1 # Ocean Interpreter - Jamison Creek version
3 Ocean is intended to be a compiled language, so this interpreter is
4 not targeted at being the final product. It is, rather, an intermediate
5 stage and fills that role in two distinct ways.
7 Firstly, it exists as a platform to experiment with the early language
8 design. An interpreter is easy to write and easy to get working, so
9 the barrier for entry is lower if I aim to start with an interpreter.
11 Secondly, the plan for the Ocean compiler is to write it in the
12 [Ocean language](http://ocean-lang.org). To achieve this we naturally
13 need some sort of boot-strap process and this interpreter - written in
14 portable C - will fill that role. It will be used to bootstrap the
17 Two features that are not needed to fill either of these roles are
18 performance and completeness. The interpreter only needs to be fast
19 enough to run small test programs and occasionally to run the compiler
20 on itself. It only needs to be complete enough to test aspects of the
21 design which are developed before the compiler is working, and to run
22 the compiler on itself. Any features not used by the compiler when
23 compiling itself are superfluous. They may be included anyway, but
26 Nonetheless, the interpreter should end up being reasonably complete,
27 and any performance bottlenecks which appear and are easily fixed, will
32 This third version of the interpreter exists to test out some initial
33 ideas relating to types. Particularly it adds arrays (indexed from
34 zero) and simple structures. Basic control flow and variable scoping
35 are already fairly well established, as are basic numerical and
38 Some operators that have only recently been added, and so have not
39 generated all that much experience yet are "and then" and "or else" as
40 short-circuit Boolean operators, and the "if ... else" trinary
41 operator which can select between two expressions based on a third
42 (which appears syntactically in the middle).
44 The "func" clause currently only allows a "main" function to be
45 declared. That will be extended when proper function support is added.
47 An element that is present purely to make a usable language, and
48 without any expectation that they will remain, is the "print" statement
49 which performs simple output.
51 The current scalar types are "number", "Boolean", and "string".
52 Boolean will likely stay in its current form, the other two might, but
53 could just as easily be changed.
57 Versions of the interpreter which obviously do not support a complete
58 language will be named after creeks and streams. This one is Jamison
61 Once we have something reasonably resembling a complete language, the
62 names of rivers will be used.
63 Early versions of the compiler will be named after seas. Major
64 releases of the compiler will be named after oceans. Hopefully I will
65 be finished once I get to the Pacific Ocean release.
69 As well as parsing and executing a program, the interpreter can print
70 out the program from the parsed internal structure. This is useful
71 for validating the parsing.
72 So the main requirements of the interpreter are:
74 - Parse the program, possibly with tracing,
75 - Analyse the parsed program to ensure consistency,
77 - Execute the "main" function in the program, if no parsing or
78 consistency errors were found.
80 This is all performed by a single C program extracted with
83 There will be two formats for printing the program: a default and one
84 that uses bracketing. So a `--bracket` command line option is needed
85 for that. Normally the first code section found is used, however an
86 alternate section can be requested so that a file (such as this one)
87 can contain multiple programs. This is effected with the `--section`
90 This code must be compiled with `-fplan9-extensions` so that anonymous
91 structures can be used.
93 ###### File: oceani.mk
95 myCFLAGS := -Wall -g -fplan9-extensions
96 CFLAGS := $(filter-out $(myCFLAGS),$(CFLAGS)) $(myCFLAGS)
97 myLDLIBS:= libparser.o libscanner.o libmdcode.o -licuuc
98 LDLIBS := $(filter-out $(myLDLIBS),$(LDLIBS)) $(myLDLIBS)
100 all :: $(LDLIBS) oceani
101 oceani.c oceani.h : oceani.mdc parsergen
102 ./parsergen -o oceani --LALR --tag Parser oceani.mdc
103 oceani.mk: oceani.mdc md2c
106 oceani: oceani.o $(LDLIBS)
107 $(CC) $(CFLAGS) -o oceani oceani.o $(LDLIBS)
109 ###### Parser: header
111 struct parse_context;
114 struct parse_context {
115 struct token_config config;
123 #define container_of(ptr, type, member) ({ \
124 const typeof( ((type *)0)->member ) *__mptr = (ptr); \
125 (type *)( (char *)__mptr - offsetof(type,member) );})
127 #define config2context(_conf) container_of(_conf, struct parse_context, \
130 ###### Parser: reduce
131 struct parse_context *c = config2context(config);
139 #include <sys/mman.h>
158 static char Usage[] =
159 "Usage: oceani --trace --print --noexec --brackets --section=SectionName prog.ocn\n";
160 static const struct option long_options[] = {
161 {"trace", 0, NULL, 't'},
162 {"print", 0, NULL, 'p'},
163 {"noexec", 0, NULL, 'n'},
164 {"brackets", 0, NULL, 'b'},
165 {"section", 1, NULL, 's'},
168 const char *options = "tpnbs";
170 static void pr_err(char *msg) // NOTEST
172 fprintf(stderr, "%s\n", msg); // NOTEST
175 int main(int argc, char *argv[])
180 struct section *s = NULL, *ss;
181 char *section = NULL;
182 struct parse_context context = {
184 .ignored = (1 << TK_mark),
185 .number_chars = ".,_+- ",
190 int doprint=0, dotrace=0, doexec=1, brackets=0;
192 while ((opt = getopt_long(argc, argv, options, long_options, NULL))
195 case 't': dotrace=1; break;
196 case 'p': doprint=1; break;
197 case 'n': doexec=0; break;
198 case 'b': brackets=1; break;
199 case 's': section = optarg; break;
200 default: fprintf(stderr, Usage);
204 if (optind >= argc) {
205 fprintf(stderr, "oceani: no input file given\n");
208 fd = open(argv[optind], O_RDONLY);
210 fprintf(stderr, "oceani: cannot open %s\n", argv[optind]);
213 context.file_name = argv[optind];
214 len = lseek(fd, 0, 2);
215 file = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
216 s = code_extract(file, file+len, pr_err);
218 fprintf(stderr, "oceani: could not find any code in %s\n",
223 ## context initialization
226 for (ss = s; ss; ss = ss->next) {
227 struct text sec = ss->section;
228 if (sec.len == strlen(section) &&
229 strncmp(sec.txt, section, sec.len) == 0)
233 fprintf(stderr, "oceani: cannot find section %s\n",
240 fprintf(stderr, "oceani: no code found in requested section\n"); // NOTEST
241 goto cleanup; // NOTEST
244 parse_oceani(ss->code, &context.config, dotrace ? stderr : NULL);
246 resolve_consts(&context);
247 prepare_types(&context);
248 if (!context.parse_error && !analyse_funcs(&context)) {
249 fprintf(stderr, "oceani: type error in program - not running.\n");
250 context.parse_error += 1;
258 if (doexec && !context.parse_error)
259 interp_main(&context, argc - optind, argv + optind);
262 struct section *t = s->next;
267 // FIXME parser should pop scope even on error
268 while (context.scope_depth > 0)
272 ## free context types
273 ## free context storage
274 exit(context.parse_error ? 1 : 0);
279 The four requirements of parse, analyse, print, interpret apply to
280 each language element individually so that is how most of the code
283 Three of the four are fairly self explanatory. The one that requires
284 a little explanation is the analysis step.
286 The current language design does not require the types of variables to
287 be declared, but they must still have a single type. Different
288 operations impose different requirements on the variables, for example
289 addition requires both arguments to be numeric, and assignment
290 requires the variable on the left to have the same type as the
291 expression on the right.
293 Analysis involves propagating these type requirements around and
294 consequently setting the type of each variable. If any requirements
295 are violated (e.g. a string is compared with a number) or if a
296 variable needs to have two different types, then an error is raised
297 and the program will not run.
299 If the same variable is declared in both branchs of an 'if/else', or
300 in all cases of a 'switch' then the multiple instances may be merged
301 into just one variable if the variable is referenced after the
302 conditional statement. When this happens, the types must naturally be
303 consistent across all the branches. When the variable is not used
304 outside the if, the variables in the different branches are distinct
305 and can be of different types.
307 Undeclared names may only appear in "use" statements and "case" expressions.
308 These names are given a type of "label" and a unique value.
309 This allows them to fill the role of a name in an enumerated type, which
310 is useful for testing the `switch` statement.
312 As we will see, the condition part of a `while` statement can return
313 either a Boolean or some other type. This requires that the expected
314 type that gets passed around comprises a type and a flag to indicate
315 that `Tbool` is also permitted.
317 As there are, as yet, no distinct types that are compatible, there
318 isn't much subtlety in the analysis. When we have distinct number
319 types, this will become more interesting.
323 When analysis discovers an inconsistency it needs to report an error;
324 just refusing to run the code ensures that the error doesn't cascade,
325 but by itself it isn't very useful. A clear understanding of the sort
326 of error message that are useful will help guide the process of
329 At a simplistic level, the only sort of error that type analysis can
330 report is that the type of some construct doesn't match a contextual
331 requirement. For example, in `4 + "hello"` the addition provides a
332 contextual requirement for numbers, but `"hello"` is not a number. In
333 this particular example no further information is needed as the types
334 are obvious from local information. When a variable is involved that
335 isn't the case. It may be helpful to explain why the variable has a
336 particular type, by indicating the location where the type was set,
337 whether by declaration or usage.
339 Using a recursive-descent analysis we can easily detect a problem at
340 multiple locations. In "`hello:= "there"; 4 + hello`" the addition
341 will detect that one argument is not a number and the usage of `hello`
342 will detect that a number was wanted, but not provided. In this
343 (early) version of the language, we will generate error reports at
344 multiple locations, so the use of `hello` will report an error and
345 explain were the value was set, and the addition will report an error
346 and say why numbers are needed. To be able to report locations for
347 errors, each language element will need to record a file location
348 (line and column) and each variable will need to record the language
349 element where its type was set. For now we will assume that each line
350 of an error message indicates one location in the file, and up to 2
351 types. So we provide a `printf`-like function which takes a format, a
352 location (a `struct exec` which has not yet been introduced), and 2
353 types. "`%1`" reports the first type, "`%2`" reports the second. We
354 will need a function to print the location, once we know how that is
355 stored. e As will be explained later, there are sometimes extra rules for
356 type matching and they might affect error messages, we need to pass those
359 As well as type errors, we sometimes need to report problems with
360 tokens, which might be unexpected or might name a type that has not
361 been defined. For these we have `tok_err()` which reports an error
362 with a given token. Each of the error functions sets the flag in the
363 context so indicate that parsing failed.
367 static void fput_loc(struct exec *loc, FILE *f);
368 static void type_err(struct parse_context *c,
369 char *fmt, struct exec *loc,
370 struct type *t1, enum val_rules rules, struct type *t2);
371 static void tok_err(struct parse_context *c, char *fmt, struct token *t);
373 ###### core functions
375 static void type_err(struct parse_context *c,
376 char *fmt, struct exec *loc,
377 struct type *t1, enum val_rules rules, struct type *t2)
379 fprintf(stderr, "%s:", c->file_name);
380 fput_loc(loc, stderr);
381 for (; *fmt ; fmt++) {
388 case '%': fputc(*fmt, stderr); break; // NOTEST
389 default: fputc('?', stderr); break; // NOTEST
391 type_print(t1, stderr);
394 type_print(t2, stderr);
403 static void tok_err(struct parse_context *c, char *fmt, struct token *t)
405 fprintf(stderr, "%s:%d:%d: %s: %.*s\n", c->file_name, t->line, t->col, fmt,
406 t->txt.len, t->txt.txt);
410 ## Entities: declared and predeclared.
412 There are various "things" that the language and/or the interpreter
413 needs to know about to parse and execute a program. These include
414 types, variables, values, and executable code. These are all lumped
415 together under the term "entities" (calling them "objects" would be
416 confusing) and introduced here. The following section will present the
417 different specific code elements which comprise or manipulate these
422 Executables can be lots of different things. In many cases an
423 executable is just an operation combined with one or two other
424 executables. This allows for expressions and lists etc. Other times an
425 executable is something quite specific like a constant or variable name.
426 So we define a `struct exec` to be a general executable with a type, and
427 a `struct binode` which is a subclass of `exec`, forms a node in a
428 binary tree, and holds an operation. There will be other subclasses,
429 and to access these we need to be able to `cast` the `exec` into the
430 various other types. The first field in any `struct exec` is the type
431 from the `exec_types` enum.
434 #define cast(structname, pointer) ({ \
435 const typeof( ((struct structname *)0)->type) *__mptr = &(pointer)->type; \
436 if (__mptr && *__mptr != X##structname) abort(); \
437 (struct structname *)( (char *)__mptr);})
439 #define new(structname) ({ \
440 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
441 __ptr->type = X##structname; \
442 __ptr->line = -1; __ptr->column = -1; \
445 #define new_pos(structname, token) ({ \
446 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
447 __ptr->type = X##structname; \
448 __ptr->line = token.line; __ptr->column = token.col; \
457 enum exec_types type;
466 struct exec *left, *right;
471 static int __fput_loc(struct exec *loc, FILE *f)
475 if (loc->line >= 0) {
476 fprintf(f, "%d:%d: ", loc->line, loc->column);
479 if (loc->type == Xbinode)
480 return __fput_loc(cast(binode,loc)->left, f) ||
481 __fput_loc(cast(binode,loc)->right, f); // NOTEST
484 static void fput_loc(struct exec *loc, FILE *f)
486 if (!__fput_loc(loc, f))
487 fprintf(f, "??:??: "); // NOTEST
490 Each different type of `exec` node needs a number of functions defined,
491 a bit like methods. We must be able to free it, print it, analyse it
492 and execute it. Once we have specific `exec` types we will need to
493 parse them too. Let's take this a bit more slowly.
497 The parser generator requires a `free_foo` function for each struct
498 that stores attributes and they will often be `exec`s and subtypes
499 there-of. So we need `free_exec` which can handle all the subtypes,
500 and we need `free_binode`.
504 static void free_binode(struct binode *b)
513 ###### core functions
514 static void free_exec(struct exec *e)
525 static void free_exec(struct exec *e);
527 ###### free exec cases
528 case Xbinode: free_binode(cast(binode, e)); break;
532 Printing an `exec` requires that we know the current indent level for
533 printing line-oriented components. As will become clear later, we
534 also want to know what sort of bracketing to use.
538 static void do_indent(int i, char *str)
545 ###### core functions
546 static void print_binode(struct binode *b, int indent, int bracket)
550 ## print binode cases
554 static void print_exec(struct exec *e, int indent, int bracket)
560 print_binode(cast(binode, e), indent, bracket); break;
565 do_indent(indent, "/* FREE");
566 for (v = e->to_free; v; v = v->next_free) {
567 printf(" %.*s", v->name->name.len, v->name->name.txt);
568 printf("[%d,%d]", v->scope_start, v->scope_end);
569 if (v->frame_pos >= 0)
570 printf("(%d+%d)", v->frame_pos,
571 v->type ? v->type->size:0);
579 static void print_exec(struct exec *e, int indent, int bracket);
583 As discussed, analysis involves propagating type requirements around the
584 program and looking for errors.
586 So `propagate_types` is passed an expected type (being a `struct type`
587 pointer together with some `val_rules` flags) that the `exec` is
588 expected to return, and returns the type that it does return, either of
589 which can be `NULL` signifying "unknown". A `prop_err` flag set is
590 passed by reference. It has `Efail` set when an error is found, and
591 `Eretry` when the type for some element is set via propagation. If
592 any expression cannot be evaluated a compile time, `Eruntime` is set.
593 If the expression can be copied, `Emaycopy` is set.
595 If `Erval` is set, then the value cannot be assigned to because it is
596 a temporary result. If `Erval` is clear but `Econst` is set, then
597 the value can only be assigned once, when the variable is declared.
601 enum val_rules {Rboolok = 1<<0, Rrefok = 1<<1,};
602 enum prop_err {Efail = 1<<0, Eretry = 1<<1, Eruntime = 1<<2,
603 Emaycopy = 1<<3, Erval = 1<<4, Econst = 1<<5};
606 static struct type *propagate_types(struct exec *prog, struct parse_context *c, enum prop_err *perr,
607 struct type *type, enum val_rules rules);
608 ###### core functions
610 static struct type *__propagate_types(struct exec *prog, struct parse_context *c, enum prop_err *perr,
611 enum prop_err *perr_local,
612 struct type *type, enum val_rules rules)
619 switch (prog->type) {
622 struct binode *b = cast(binode, prog);
624 ## propagate binode cases
628 ## propagate exec cases
633 static struct type *propagate_types(struct exec *prog, struct parse_context *c, enum prop_err *perr,
634 struct type *type, enum val_rules rules)
636 int pre_err = c->parse_error;
637 enum prop_err perr_local = 0;
638 struct type *ret = __propagate_types(prog, c, perr, &perr_local, type, rules);
640 *perr |= perr_local & (Efail | Eretry);
641 if (c->parse_error > pre_err)
648 Interpreting an `exec` doesn't require anything but the `exec`. State
649 is stored in variables and each variable will be directly linked from
650 within the `exec` tree. The exception to this is the `main` function
651 which needs to look at command line arguments. This function will be
652 interpreted separately.
654 Each `exec` can return a value combined with a type in `struct lrval`.
655 The type may be `Tnone` but must be non-NULL. Some `exec`s will return
656 the location of a value, which can be updated, in `lval`. Others will
657 set `lval` to NULL indicating that there is a value of appropriate type
661 static struct value interp_exec(struct parse_context *c, struct exec *e,
662 struct type **typeret);
663 ###### core functions
667 struct value rval, *lval;
670 /* If dest is passed, dtype must give the expected type, and
671 * result can go there, in which case type is returned as NULL.
673 static struct lrval _interp_exec(struct parse_context *c, struct exec *e,
674 struct value *dest, struct type *dtype);
676 static struct value interp_exec(struct parse_context *c, struct exec *e,
677 struct type **typeret)
679 struct lrval ret = _interp_exec(c, e, NULL, NULL);
681 if (!ret.type) abort();
685 dup_value(ret.type, ret.lval, &ret.rval);
689 static struct value *linterp_exec(struct parse_context *c, struct exec *e,
690 struct type **typeret)
692 struct lrval ret = _interp_exec(c, e, NULL, NULL);
694 if (!ret.type) abort();
698 free_value(ret.type, &ret.rval);
702 /* dinterp_exec is used when the destination type is certain and
703 * the value has a place to go.
705 static void dinterp_exec(struct parse_context *c, struct exec *e,
706 struct value *dest, struct type *dtype,
709 struct lrval ret = _interp_exec(c, e, dest, dtype);
713 free_value(dtype, dest);
715 dup_value(dtype, ret.lval, dest);
717 memcpy(dest, &ret.rval, dtype->size);
720 static struct lrval _interp_exec(struct parse_context *c, struct exec *e,
721 struct value *dest, struct type *dtype)
723 /* If the result is copied to dest, ret.type is set to NULL */
725 struct value rv = {}, *lrv = NULL;
728 rvtype = ret.type = Tnone;
738 struct binode *b = cast(binode, e);
739 struct value left, right, *lleft;
740 struct type *ltype, *rtype;
741 ltype = rtype = Tnone;
743 ## interp binode cases
745 free_value(ltype, &left);
746 free_value(rtype, &right);
756 ## interp exec cleanup
762 Values come in a wide range of types, with more likely to be added.
763 Each type needs to be able to print its own values (for convenience at
764 least) as well as to compare two values, at least for equality and
765 possibly for order. For now, values might need to be duplicated and
766 freed, though eventually such manipulations will be better integrated
769 Rather than requiring every numeric type to support all numeric
770 operations (add, multiply, etc), we allow types to be able to present
771 as one of a few standard types: integer, float, and fraction. The
772 existence of these conversion functions eventually enable types to
773 determine if they are compatible with other types, though such types
774 have not yet been implemented.
776 Named type are stored in a simple linked list. Objects of each type are
777 "values" which are often passed around by value.
779 There are both explicitly named types, and anonymous types. Anonymous
780 cannot be accessed by name, but are used internally and have a name
781 which might be reported in error messages.
788 ## value union fields
796 struct token first_use;
799 void (*init)(struct type *type, struct value *val);
800 int (*prepare_type)(struct parse_context *c, struct type *type, int parse_time);
801 void (*print)(struct type *type, struct value *val, FILE *f);
802 void (*print_type)(struct type *type, FILE *f);
803 int (*cmp_order)(struct type *t1, struct type *t2,
804 struct value *v1, struct value *v2);
805 int (*cmp_eq)(struct type *t1, struct type *t2,
806 struct value *v1, struct value *v2);
807 void (*dup)(struct type *type, struct value *vold, struct value *vnew);
808 int (*test)(struct type *type, struct value *val);
809 void (*free)(struct type *type, struct value *val);
810 void (*free_type)(struct type *t);
811 long long (*to_int)(struct value *v);
812 double (*to_float)(struct value *v);
813 int (*to_mpq)(mpq_t *q, struct value *v);
822 struct type *typelist;
829 static struct type *find_type(struct parse_context *c, struct text s)
831 struct type *t = c->typelist;
833 while (t && (t->anon ||
834 text_cmp(t->name, s) != 0))
839 static struct type *_add_type(struct parse_context *c, struct text s,
840 struct type *proto, int anon)
844 n = calloc(1, sizeof(*n));
851 n->next = c->typelist;
856 static struct type *add_type(struct parse_context *c, struct text s,
859 return _add_type(c, s, proto, 0);
862 static struct type *add_anon_type(struct parse_context *c,
863 struct type *proto, char *name, ...)
869 vasprintf(&t.txt, name, ap);
871 t.len = strlen(t.txt);
872 return _add_type(c, t, proto, 1);
875 static struct type *find_anon_type(struct parse_context *c,
876 struct type *proto, char *name, ...)
878 struct type *t = c->typelist;
883 vasprintf(&nm.txt, name, ap);
885 nm.len = strlen(name);
887 while (t && (!t->anon ||
888 text_cmp(t->name, nm) != 0))
894 return _add_type(c, nm, proto, 1);
897 static void free_type(struct type *t)
899 /* The type is always a reference to something in the
900 * context, so we don't need to free anything.
904 static void free_value(struct type *type, struct value *v)
908 memset(v, 0x5a, type->size);
912 static void type_print(struct type *type, FILE *f)
915 fputs("*unknown*type*", f); // NOTEST
916 else if (type->name.len && !type->anon)
917 fprintf(f, "%.*s", type->name.len, type->name.txt);
918 else if (type->print_type)
919 type->print_type(type, f);
920 else if (type->name.len && type->anon)
921 fprintf(f, "\"%.*s\"", type->name.len, type->name.txt);
923 fputs("*invalid*type*", f); // NOTEST
926 static void val_init(struct type *type, struct value *val)
928 if (type && type->init)
929 type->init(type, val);
932 static void dup_value(struct type *type,
933 struct value *vold, struct value *vnew)
935 if (type && type->dup)
936 type->dup(type, vold, vnew);
939 static int value_cmp(struct type *tl, struct type *tr,
940 struct value *left, struct value *right)
942 if (tl && tl->cmp_order)
943 return tl->cmp_order(tl, tr, left, right);
944 if (tl && tl->cmp_eq)
945 return tl->cmp_eq(tl, tr, left, right);
949 static void print_value(struct type *type, struct value *v, FILE *f)
951 if (type && type->print)
952 type->print(type, v, f);
954 fprintf(f, "*Unknown*"); // NOTEST
957 static void prepare_types(struct parse_context *c)
961 enum { none, some, cannot } progress = none;
966 for (t = c->typelist; t; t = t->next) {
968 tok_err(c, "error: type used but not declared",
970 if (t->size == 0 && t->prepare_type) {
971 if (t->prepare_type(c, t, 1))
973 else if (progress == cannot)
974 tok_err(c, "error: type has recursive definition",
984 progress = cannot; break;
986 progress = none; break;
993 static void free_value(struct type *type, struct value *v);
994 static int type_compat(struct type *require, struct type *have, enum val_rules rules);
995 static void type_print(struct type *type, FILE *f);
996 static void val_init(struct type *type, struct value *v);
997 static void dup_value(struct type *type,
998 struct value *vold, struct value *vnew);
999 static int value_cmp(struct type *tl, struct type *tr,
1000 struct value *left, struct value *right);
1001 static void print_value(struct type *type, struct value *v, FILE *f);
1003 ###### free context types
1005 while (context.typelist) {
1006 struct type *t = context.typelist;
1008 context.typelist = t->next;
1016 Type can be specified for local variables, for fields in a structure,
1017 for formal parameters to functions, and possibly elsewhere. Different
1018 rules may apply in different contexts. As a minimum, a named type may
1019 always be used. Currently the type of a formal parameter can be
1020 different from types in other contexts, so we have a separate grammar
1026 Type -> IDENTIFIER ${
1027 $0 = find_type(c, $ID.txt);
1029 $0 = add_type(c, $ID.txt, NULL);
1030 $0->first_use = $ID;
1035 FormalType -> Type ${ $0 = $<1; }$
1036 ## formal type grammar
1040 Values of the base types can be numbers, which we represent as
1041 multi-precision fractions, strings, Booleans and labels. When
1042 analysing the program we also need to allow for places where no value
1043 is meaningful (type `Tnone`) and where we don't know what type to
1044 expect yet (type is `NULL`).
1046 Values are never shared, they are always copied when used, and freed
1047 when no longer needed.
1049 When propagating type information around the program, we need to
1050 determine if two types are compatible, where type `NULL` is compatible
1051 with anything. There are two special cases with type compatibility,
1052 both related to the Conditional Statement which will be described
1053 later. In some cases a Boolean can be accepted as well as some other
1054 primary type, and in others any type is acceptable except a label (`Vlabel`).
1055 A separate function encoding these cases will simplify some code later.
1057 ###### type functions
1059 int (*compat)(struct type *this, struct type *other, enum val_rules rules);
1061 ###### ast functions
1063 static int type_compat(struct type *require, struct type *have,
1064 enum val_rules rules)
1066 if ((rules & Rboolok) && have == Tbool)
1068 if (!require || !have)
1071 if (require->compat)
1072 return require->compat(require, have, rules);
1074 return require == have;
1079 #include "parse_string.h"
1080 #include "parse_number.h"
1083 myLDLIBS := libnumber.o libstring.o -lgmp
1084 LDLIBS := $(filter-out $(myLDLIBS),$(LDLIBS)) $(myLDLIBS)
1086 ###### type union fields
1087 enum vtype {Vnone, Vstr, Vnum, Vbool, Vlabel} vtype;
1089 ###### value union fields
1095 ###### ast functions
1096 static void _free_value(struct type *type, struct value *v)
1100 switch (type->vtype) {
1102 case Vstr: free(v->str.txt); break;
1103 case Vnum: mpq_clear(v->num); break;
1109 ###### value functions
1111 static void _val_init(struct type *type, struct value *val)
1113 switch(type->vtype) {
1114 case Vnone: // NOTEST
1117 mpq_init(val->num); break;
1119 val->str.txt = malloc(1);
1126 val->label = 0; // NOTEST
1131 static void _dup_value(struct type *type,
1132 struct value *vold, struct value *vnew)
1134 switch (type->vtype) {
1135 case Vnone: // NOTEST
1138 vnew->label = vold->label; // NOTEST
1141 vnew->bool = vold->bool;
1144 mpq_init(vnew->num);
1145 mpq_set(vnew->num, vold->num);
1148 vnew->str.len = vold->str.len;
1149 vnew->str.txt = malloc(vnew->str.len);
1150 memcpy(vnew->str.txt, vold->str.txt, vnew->str.len);
1155 static int _value_cmp(struct type *tl, struct type *tr,
1156 struct value *left, struct value *right)
1160 return tl - tr; // NOTEST
1161 switch (tl->vtype) {
1162 case Vlabel: cmp = left->label == right->label ? 0 : 1; break;
1163 case Vnum: cmp = mpq_cmp(left->num, right->num); break;
1164 case Vstr: cmp = text_cmp(left->str, right->str); break;
1165 case Vbool: cmp = left->bool - right->bool; break;
1166 case Vnone: cmp = 0; // NOTEST
1171 static void _print_value(struct type *type, struct value *v, FILE *f)
1173 switch (type->vtype) {
1174 case Vnone: // NOTEST
1175 fprintf(f, "*no-value*"); break; // NOTEST
1176 case Vlabel: // NOTEST
1177 fprintf(f, "*label-%d*", v->label); break; // NOTEST
1179 fprintf(f, "%.*s", v->str.len, v->str.txt); break;
1181 fprintf(f, "%s", v->bool ? "True":"False"); break;
1186 mpf_set_q(fl, v->num);
1187 gmp_fprintf(f, "%.10Fg", fl);
1194 static void _free_value(struct type *type, struct value *v);
1196 static int bool_test(struct type *type, struct value *v)
1201 static struct type base_prototype = {
1203 .print = _print_value,
1204 .cmp_order = _value_cmp,
1205 .cmp_eq = _value_cmp,
1207 .free = _free_value,
1210 static struct type *Tbool, *Tstr, *Tnum, *Tnone, *Tlabel;
1212 ###### ast functions
1213 static struct type *add_base_type(struct parse_context *c, char *n,
1214 enum vtype vt, int size)
1216 struct text txt = { n, strlen(n) };
1219 t = add_type(c, txt, &base_prototype);
1222 t->align = size > sizeof(void*) ? sizeof(void*) : size;
1223 if (t->size & (t->align - 1))
1224 t->size = (t->size | (t->align - 1)) + 1; // NOTEST
1228 ###### context initialization
1230 Tbool = add_base_type(&context, "Boolean", Vbool, sizeof(char));
1231 Tbool->test = bool_test;
1232 Tstr = add_base_type(&context, "string", Vstr, sizeof(struct text));
1233 Tnum = add_base_type(&context, "number", Vnum, sizeof(mpq_t));
1234 Tnone = add_base_type(&context, "none", Vnone, 0);
1235 Tlabel = add_base_type(&context, "label", Vlabel, sizeof(void*));
1239 We have already met values as separate objects. When manifest constants
1240 appear in the program text, that must result in an executable which has
1241 a constant value. So the `val` structure embeds a value in an
1254 ###### ast functions
1255 struct val *new_val(struct type *T, struct token tk)
1257 struct val *v = new_pos(val, tk);
1262 ###### declare terminals
1269 $0 = new_val(Tbool, $1);
1273 $0 = new_val(Tbool, $1);
1278 $0 = new_val(Tnum, $1);
1279 if (number_parse($0->val.num, tail, $1.txt) == 0) {
1280 mpq_init($0->val.num);
1281 tok_err(c, "error: unsupported number format", &$NUM);
1283 tok_err(c, "error: unsupported number suffix", &$1);
1287 $0 = new_val(Tstr, $1);
1288 string_parse(&$1, '\\', &$0->val.str, tail);
1290 tok_err(c, "error: unsupported string suffix",
1295 $0 = new_val(Tstr, $1);
1296 string_parse(&$1, '\\', &$0->val.str, tail);
1298 tok_err(c, "error: unsupported string suffix",
1302 ###### print exec cases
1305 struct val *v = cast(val, e);
1306 if (v->vtype == Tstr)
1308 // FIXME how to ensure numbers have same precision.
1309 print_value(v->vtype, &v->val, stdout);
1310 if (v->vtype == Tstr)
1315 ###### propagate exec cases
1318 struct val *val = cast(val, prog);
1319 if (!type_compat(type, val->vtype, rules))
1320 type_err(c, "error: expected %1 found %2",
1321 prog, type, rules, val->vtype);
1326 ###### interp exec cases
1328 rvtype = cast(val, e)->vtype;
1329 dup_value(rvtype, &cast(val, e)->val, &rv);
1332 ###### ast functions
1333 static void free_val(struct val *v)
1336 free_value(v->vtype, &v->val);
1340 ###### free exec cases
1341 case Xval: free_val(cast(val, e)); break;
1343 ###### ast functions
1344 // Move all nodes from 'b' to 'rv', reversing their order.
1345 // In 'b' 'left' is a list, and 'right' is the last node.
1346 // In 'rv', left' is the first node and 'right' is a list.
1347 static struct binode *reorder_bilist(struct binode *b)
1349 struct binode *rv = NULL;
1352 struct exec *t = b->right;
1356 b = cast(binode, b->left);
1366 Labels are a temporary concept until I implement enums. There are an
1367 anonymous enum which is declared by usage. Thet are only allowed in
1368 `use` statements and corresponding `case` entries. They appear as a
1369 period followed by an identifier. All identifiers that are "used" must
1372 For now, we have a global list of labels, and don't check that all "use"
1384 ###### free exec cases
1388 ###### print exec cases
1390 struct label *l = cast(label, e);
1391 printf(".%.*s", l->name.len, l->name.txt);
1397 struct labels *next;
1401 ###### parse context
1402 struct labels *labels;
1404 ###### ast functions
1405 static int label_lookup(struct parse_context *c, struct text name)
1407 struct labels *l, **lp = &c->labels;
1408 while (*lp && text_cmp((*lp)->name, name) < 0)
1410 if (*lp && text_cmp((*lp)->name, name) == 0)
1411 return (*lp)->value;
1412 l = calloc(1, sizeof(*l));
1415 if (c->next_label == 0)
1417 l->value = c->next_label;
1423 ###### free context storage
1424 while (context.labels) {
1425 struct labels *l = context.labels;
1426 context.labels = l->next;
1430 ###### declare terminals
1434 struct label *l = new_pos(label, $ID);
1438 ###### propagate exec cases
1440 struct label *l = cast(label, prog);
1441 l->value = label_lookup(c, l->name);
1442 if (!type_compat(type, Tlabel, rules))
1443 type_err(c, "error: expected %1 found %2",
1444 prog, type, rules, Tlabel);
1448 ###### interp exec cases
1450 struct label *l = cast(label, e);
1451 rv.label = l->value;
1459 Variables are scoped named values. We store the names in a linked list
1460 of "bindings" sorted in lexical order, and use sequential search and
1467 struct binding *next; // in lexical order
1471 This linked list is stored in the parse context so that "reduce"
1472 functions can find or add variables, and so the analysis phase can
1473 ensure that every variable gets a type.
1475 ###### parse context
1477 struct binding *varlist; // In lexical order
1479 ###### ast functions
1481 static struct binding *find_binding(struct parse_context *c, struct text s)
1483 struct binding **l = &c->varlist;
1488 (cmp = text_cmp((*l)->name, s)) < 0)
1492 n = calloc(1, sizeof(*n));
1499 Each name can be linked to multiple variables defined in different
1500 scopes. Each scope starts where the name is declared and continues
1501 until the end of the containing code block. Scopes of a given name
1502 cannot nest, so a declaration while a name is in-scope is an error.
1504 ###### binding fields
1505 struct variable *var;
1509 struct variable *previous;
1511 struct binding *name;
1512 struct exec *where_decl;// where name was declared
1513 struct exec *where_set; // where type was set
1517 When a scope closes, the values of the variables might need to be freed.
1518 This happens in the context of some `struct exec` and each `exec` will
1519 need to know which variables need to be freed when it completes.
1522 struct variable *to_free;
1524 ####### variable fields
1525 struct exec *cleanup_exec;
1526 struct variable *next_free;
1528 ####### interp exec cleanup
1531 for (v = e->to_free; v; v = v->next_free) {
1532 struct value *val = var_value(c, v);
1533 free_value(v->type, val);
1537 ###### ast functions
1538 static void variable_unlink_exec(struct variable *v)
1540 struct variable **vp;
1541 if (!v->cleanup_exec)
1543 for (vp = &v->cleanup_exec->to_free;
1544 *vp; vp = &(*vp)->next_free) {
1548 v->cleanup_exec = NULL;
1553 While the naming seems strange, we include local constants in the
1554 definition of variables. A name declared `var := value` can
1555 subsequently be changed, but a name declared `var ::= value` cannot -
1558 ###### variable fields
1561 Scopes in parallel branches can be partially merged. More
1562 specifically, if a given name is declared in both branches of an
1563 if/else then its scope is a candidate for merging. Similarly if
1564 every branch of an exhaustive switch (e.g. has an "else" clause)
1565 declares a given name, then the scopes from the branches are
1566 candidates for merging.
1568 Note that names declared inside a loop (which is only parallel to
1569 itself) are never visible after the loop. Similarly names defined in
1570 scopes which are not parallel, such as those started by `for` and
1571 `switch`, are never visible after the scope. Only variables defined in
1572 both `then` and `else` (including the implicit then after an `if`, and
1573 excluding `then` used with `for`) and in all `case`s and `else` of a
1574 `switch` or `while` can be visible beyond the `if`/`switch`/`while`.
1576 Labels, which are a bit like variables, follow different rules.
1577 Labels are not explicitly declared, but if an undeclared name appears
1578 in a context where a label is legal, that effectively declares the
1579 name as a label. The declaration remains in force (or in scope) at
1580 least to the end of the immediately containing block and conditionally
1581 in any larger containing block which does not declare the name in some
1582 other way. Importantly, the conditional scope extension happens even
1583 if the label is only used in one parallel branch of a conditional --
1584 when used in one branch it is treated as having been declared in all
1587 Merge candidates are tentatively visible beyond the end of the
1588 branching statement which creates them. If the name is used, the
1589 merge is affirmed and they become a single variable visible at the
1590 outer layer. If not - if it is redeclared first - the merge lapses.
1592 To track scopes we have an extra stack, implemented as a linked list,
1593 which roughly parallels the parse stack and which is used exclusively
1594 for scoping. When a new scope is opened, a new frame is pushed and
1595 the child-count of the parent frame is incremented. This child-count
1596 is used to distinguish between the first of a set of parallel scopes,
1597 in which declared variables must not be in scope, and subsequent
1598 branches, whether they may already be conditionally scoped.
1600 We need a total ordering of scopes so we can easily compare to variables
1601 to see if they are concurrently in scope. To achieve this we record a
1602 `scope_count` which is actually a count of both beginnings and endings
1603 of scopes. Then each variable has a record of the scope count where it
1604 enters scope, and where it leaves.
1606 To push a new frame *before* any code in the frame is parsed, we need a
1607 grammar reduction. This is most easily achieved with a grammar
1608 element which derives the empty string, and creates the new scope when
1609 it is recognised. This can be placed, for example, between a keyword
1610 like "if" and the code following it.
1614 struct scope *parent;
1618 ###### parse context
1621 struct scope *scope_stack;
1623 ###### variable fields
1624 int scope_start, scope_end;
1626 ###### ast functions
1627 static void scope_pop(struct parse_context *c)
1629 struct scope *s = c->scope_stack;
1631 c->scope_stack = s->parent;
1633 c->scope_depth -= 1;
1634 c->scope_count += 1;
1637 static void scope_push(struct parse_context *c)
1639 struct scope *s = calloc(1, sizeof(*s));
1641 c->scope_stack->child_count += 1;
1642 s->parent = c->scope_stack;
1644 c->scope_depth += 1;
1645 c->scope_count += 1;
1651 OpenScope -> ${ scope_push(c); }$
1653 Each variable records a scope depth and is in one of four states:
1655 - "in scope". This is the case between the declaration of the
1656 variable and the end of the containing block, and also between
1657 the usage with affirms a merge and the end of that block.
1659 The scope depth is not greater than the current parse context scope
1660 nest depth. When the block of that depth closes, the state will
1661 change. To achieve this, all "in scope" variables are linked
1662 together as a stack in nesting order.
1664 - "pending". The "in scope" block has closed, but other parallel
1665 scopes are still being processed. So far, every parallel block at
1666 the same level that has closed has declared the name.
1668 The scope depth is the depth of the last parallel block that
1669 enclosed the declaration, and that has closed.
1671 - "conditionally in scope". The "in scope" block and all parallel
1672 scopes have closed, and no further mention of the name has been seen.
1673 This state includes a secondary nest depth (`min_depth`) which records
1674 the outermost scope seen since the variable became conditionally in
1675 scope. If a use of the name is found, the variable becomes "in scope"
1676 and that secondary depth becomes the recorded scope depth. If the
1677 name is declared as a new variable, the old variable becomes "out of
1678 scope" and the recorded scope depth stays unchanged.
1680 - "out of scope". The variable is neither in scope nor conditionally
1681 in scope. It is permanently out of scope now and can be removed from
1682 the "in scope" stack. When a variable becomes out-of-scope it is
1683 moved to a separate list (`out_scope`) of variables which have fully
1684 known scope. This will be used at the end of each function to assign
1685 each variable a place in the stack frame.
1687 ###### variable fields
1688 int depth, min_depth;
1689 enum { OutScope, PendingScope, CondScope, InScope } scope;
1690 struct variable *in_scope;
1692 ###### parse context
1694 struct variable *in_scope;
1695 struct variable *out_scope;
1697 All variables with the same name are linked together using the
1698 'previous' link. Those variable that have been affirmatively merged all
1699 have a 'merged' pointer that points to one primary variable - the most
1700 recently declared instance. When merging variables, we need to also
1701 adjust the 'merged' pointer on any other variables that had previously
1702 been merged with the one that will no longer be primary.
1704 A variable that is no longer the most recent instance of a name may
1705 still have "pending" scope, if it might still be merged with most
1706 recent instance. These variables don't really belong in the
1707 "in_scope" list, but are not immediately removed when a new instance
1708 is found. Instead, they are detected and ignored when considering the
1709 list of in_scope names.
1711 The storage of the value of a variable will be described later. For now
1712 we just need to know that when a variable goes out of scope, it might
1713 need to be freed. For this we need to be able to find it, so assume that
1714 `var_value()` will provide that.
1716 ###### variable fields
1717 struct variable *merged;
1719 ###### ast functions
1721 static void variable_merge(struct variable *primary, struct variable *secondary)
1725 primary = primary->merged;
1727 for (v = primary->previous; v; v=v->previous)
1728 if (v == secondary || v == secondary->merged ||
1729 v->merged == secondary ||
1730 v->merged == secondary->merged) {
1731 v->scope = OutScope;
1732 v->merged = primary;
1733 if (v->scope_start < primary->scope_start)
1734 primary->scope_start = v->scope_start;
1735 if (v->scope_end > primary->scope_end)
1736 primary->scope_end = v->scope_end; // NOTEST
1737 variable_unlink_exec(v);
1741 ###### forward decls
1742 static struct value *var_value(struct parse_context *c, struct variable *v);
1744 ###### free global vars
1746 while (context.varlist) {
1747 struct binding *b = context.varlist;
1748 struct variable *v = b->var;
1749 context.varlist = b->next;
1752 struct variable *next = v->previous;
1754 if (v->global && v->frame_pos >= 0) {
1755 free_value(v->type, var_value(&context, v));
1756 if (v->depth == 0 && v->type->free == function_free)
1757 // This is a function constant
1758 free_exec(v->where_decl);
1765 #### Manipulating Bindings
1767 When a name is conditionally visible, a new declaration discards the old
1768 binding - the condition lapses. Similarly when we reach the end of a
1769 function (outermost non-global scope) any conditional scope must lapse.
1770 Conversely a usage of the name affirms the visibility and extends it to
1771 the end of the containing block - i.e. the block that contains both the
1772 original declaration and the latest usage. This is determined from
1773 `min_depth`. When a conditionally visible variable gets affirmed like
1774 this, it is also merged with other conditionally visible variables with
1777 When we parse a variable declaration we either report an error if the
1778 name is currently bound, or create a new variable at the current nest
1779 depth if the name is unbound or bound to a conditionally scoped or
1780 pending-scope variable. If the previous variable was conditionally
1781 scoped, it and its homonyms becomes out-of-scope.
1783 When we parse a variable reference (including non-declarative assignment
1784 "foo = bar") we report an error if the name is not bound or is bound to
1785 a pending-scope variable; update the scope if the name is bound to a
1786 conditionally scoped variable; or just proceed normally if the named
1787 variable is in scope.
1789 When we exit a scope, any variables bound at this level are either
1790 marked out of scope or pending-scoped, depending on whether the scope
1791 was sequential or parallel. Here a "parallel" scope means the "then"
1792 or "else" part of a conditional, or any "case" or "else" branch of a
1793 switch. Other scopes are "sequential".
1795 When exiting a parallel scope we check if there are any variables that
1796 were previously pending and are still visible. If there are, then
1797 they weren't redeclared in the most recent scope, so they cannot be
1798 merged and must become out-of-scope. If it is not the first of
1799 parallel scopes (based on `child_count`), we check that there was a
1800 previous binding that is still pending-scope. If there isn't, the new
1801 variable must now be out-of-scope.
1803 When exiting a sequential scope that immediately enclosed parallel
1804 scopes, we need to resolve any pending-scope variables. If there was
1805 no `else` clause, and we cannot determine that the `switch` was exhaustive,
1806 we need to mark all pending-scope variable as out-of-scope. Otherwise
1807 all pending-scope variables become conditionally scoped.
1810 enum closetype { CloseSequential, CloseFunction, CloseParallel, CloseElse };
1812 ###### ast functions
1814 static struct variable *var_decl(struct parse_context *c, struct text s)
1816 struct binding *b = find_binding(c, s);
1817 struct variable *v = b->var;
1819 switch (v ? v->scope : OutScope) {
1821 /* Caller will report the error */
1825 v && v->scope == CondScope;
1827 v->scope = OutScope;
1831 v = calloc(1, sizeof(*v));
1832 v->previous = b->var;
1836 v->min_depth = v->depth = c->scope_depth;
1838 v->in_scope = c->in_scope;
1839 v->scope_start = c->scope_count;
1845 static struct variable *var_ref(struct parse_context *c, struct text s)
1847 struct binding *b = find_binding(c, s);
1848 struct variable *v = b->var;
1849 struct variable *v2;
1851 switch (v ? v->scope : OutScope) {
1854 /* Caller will report the error */
1857 /* All CondScope variables of this name need to be merged
1858 * and become InScope
1860 v->depth = v->min_depth;
1862 for (v2 = v->previous;
1863 v2 && v2->scope == CondScope;
1865 variable_merge(v, v2);
1873 static int var_refile(struct parse_context *c, struct variable *v)
1875 /* Variable just went out of scope. Add it to the out_scope
1876 * list, sorted by ->scope_start
1878 struct variable **vp = &c->out_scope;
1879 while ((*vp) && (*vp)->scope_start < v->scope_start)
1880 vp = &(*vp)->in_scope;
1886 static void var_block_close(struct parse_context *c, enum closetype ct,
1889 /* Close off all variables that are in_scope.
1890 * Some variables in c->scope may already be not-in-scope,
1891 * such as when a PendingScope variable is hidden by a new
1892 * variable with the same name.
1893 * So we check for v->name->var != v and drop them.
1894 * If we choose to make a variable OutScope, we drop it
1897 struct variable *v, **vp, *v2;
1900 for (vp = &c->in_scope;
1901 (v = *vp) && v->min_depth > c->scope_depth;
1902 (v->scope == OutScope || v->name->var != v)
1903 ? (*vp = v->in_scope, var_refile(c, v))
1904 : ( vp = &v->in_scope, 0)) {
1905 v->min_depth = c->scope_depth;
1906 if (v->name->var != v)
1907 /* This is still in scope, but we haven't just
1911 v->min_depth = c->scope_depth;
1912 if (v->scope == InScope)
1913 v->scope_end = c->scope_count;
1914 if (v->scope == InScope && e && !v->global) {
1915 /* This variable gets cleaned up when 'e' finishes */
1916 variable_unlink_exec(v);
1917 v->cleanup_exec = e;
1918 v->next_free = e->to_free;
1923 case CloseParallel: /* handle PendingScope */
1927 if (c->scope_stack->child_count == 1)
1928 /* first among parallel branches */
1929 v->scope = PendingScope;
1930 else if (v->previous &&
1931 v->previous->scope == PendingScope)
1932 /* all previous branches used name */
1933 v->scope = PendingScope;
1935 v->scope = OutScope;
1936 if (ct == CloseElse) {
1937 /* All Pending variables with this name
1938 * are now Conditional */
1940 v2 && v2->scope == PendingScope;
1942 v2->scope = CondScope;
1946 /* Not possible as it would require
1947 * parallel scope to be nested immediately
1948 * in a parallel scope, and that never
1952 /* Not possible as we already tested for
1959 if (v->scope == CondScope)
1960 /* Condition cannot continue past end of function */
1963 case CloseSequential:
1966 v->scope = OutScope;
1969 /* There was no 'else', so we can only become
1970 * conditional if we know the cases were exhaustive,
1971 * and that doesn't mean anything yet.
1972 * So only labels become conditional..
1975 v2 && v2->scope == PendingScope;
1977 v2->scope = OutScope;
1980 case OutScope: break;
1989 The value of a variable is store separately from the variable, on an
1990 analogue of a stack frame. There are (currently) two frames that can be
1991 active. A global frame which currently only stores constants, and a
1992 stacked frame which stores local variables. Each variable knows if it
1993 is global or not, and what its index into the frame is.
1995 Values in the global frame are known immediately they are relevant, so
1996 the frame needs to be reallocated as it grows so it can store those
1997 values. The local frame doesn't get values until the interpreted phase
1998 is started, so there is no need to allocate until the size is known.
2000 We initialize the `frame_pos` to an impossible value, so that we can
2001 tell if it was set or not later.
2003 ###### variable fields
2007 ###### variable init
2010 ###### parse context
2012 short global_size, global_alloc;
2014 void *global, *local;
2016 ###### forward decls
2017 static struct value *global_alloc(struct parse_context *c, struct type *t,
2018 struct variable *v, struct value *init);
2020 ###### ast functions
2022 static struct value *var_value(struct parse_context *c, struct variable *v)
2025 if (!c->local || !v->type)
2026 return NULL; // NOTEST
2027 if (v->frame_pos + v->type->size > c->local_size) {
2028 printf("INVALID frame_pos\n"); // NOTEST
2031 return c->local + v->frame_pos;
2033 if (c->global_size > c->global_alloc) {
2034 int old = c->global_alloc;
2035 c->global_alloc = (c->global_size | 1023) + 1024;
2036 c->global = realloc(c->global, c->global_alloc);
2037 memset(c->global + old, 0, c->global_alloc - old);
2039 return c->global + v->frame_pos;
2042 static struct value *global_alloc(struct parse_context *c, struct type *t,
2043 struct variable *v, struct value *init)
2046 struct variable scratch;
2048 if (t->prepare_type)
2049 t->prepare_type(c, t, 1); // NOTEST
2051 if (c->global_size & (t->align - 1))
2052 c->global_size = (c->global_size + t->align) & ~(t->align-1);
2057 v->frame_pos = c->global_size;
2059 c->global_size += v->type->size;
2060 ret = var_value(c, v);
2062 memcpy(ret, init, t->size);
2064 val_init(t, ret); // NOTEST
2068 As global values are found -- struct field initializers, labels etc --
2069 `global_alloc()` is called to record the value in the global frame.
2071 When the program is fully parsed, each function is analysed, we need to
2072 walk the list of variables local to that function and assign them an
2073 offset in the stack frame. For this we have `scope_finalize()`.
2075 We keep the stack from dense by re-using space for between variables
2076 that are not in scope at the same time. The `out_scope` list is sorted
2077 by `scope_start` and as we process a varible, we move it to an FIFO
2078 stack. For each variable we consider, we first discard any from the
2079 stack anything that went out of scope before the new variable came in.
2080 Then we place the new variable just after the one at the top of the
2083 ###### ast functions
2085 static void scope_finalize(struct parse_context *c, struct type *ft)
2087 int size = ft->function.local_size;
2088 struct variable *next = ft->function.scope;
2089 struct variable *done = NULL;
2092 struct variable *v = next;
2093 struct type *t = v->type;
2100 if (v->frame_pos >= 0)
2102 while (done && done->scope_end < v->scope_start)
2103 done = done->in_scope;
2105 pos = done->frame_pos + done->type->size;
2107 pos = ft->function.local_size;
2108 if (pos & (t->align - 1))
2109 pos = (pos + t->align) & ~(t->align-1);
2111 if (size < pos + v->type->size)
2112 size = pos + v->type->size;
2116 c->out_scope = NULL;
2117 ft->function.local_size = size;
2120 ###### free context storage
2121 free(context.global);
2123 #### Variables as executables
2125 Just as we used a `val` to wrap a value into an `exec`, we similarly
2126 need a `var` to wrap a `variable` into an exec. While each `val`
2127 contained a copy of the value, each `var` holds a link to the variable
2128 because it really is the same variable no matter where it appears.
2129 When a variable is used, we need to remember to follow the `->merged`
2130 link to find the primary instance.
2132 When a variable is declared, it may or may not be given an explicit
2133 type. We need to record which so that we can report the parsed code
2142 struct variable *var;
2145 ###### variable fields
2153 VariableDecl -> IDENTIFIER : ${ {
2154 struct variable *v = var_decl(c, $1.txt);
2155 $0 = new_pos(var, $1);
2160 v = var_ref(c, $1.txt);
2162 type_err(c, "error: variable '%v' redeclared",
2164 type_err(c, "info: this is where '%v' was first declared",
2165 v->where_decl, NULL, 0, NULL);
2168 | IDENTIFIER :: ${ {
2169 struct variable *v = var_decl(c, $1.txt);
2170 $0 = new_pos(var, $1);
2176 v = var_ref(c, $1.txt);
2178 type_err(c, "error: variable '%v' redeclared",
2180 type_err(c, "info: this is where '%v' was first declared",
2181 v->where_decl, NULL, 0, NULL);
2184 | IDENTIFIER : Type ${ {
2185 struct variable *v = var_decl(c, $1.txt);
2186 $0 = new_pos(var, $1);
2192 v->explicit_type = 1;
2194 v = var_ref(c, $1.txt);
2196 type_err(c, "error: variable '%v' redeclared",
2198 type_err(c, "info: this is where '%v' was first declared",
2199 v->where_decl, NULL, 0, NULL);
2202 | IDENTIFIER :: Type ${ {
2203 struct variable *v = var_decl(c, $1.txt);
2204 $0 = new_pos(var, $1);
2211 v->explicit_type = 1;
2213 v = var_ref(c, $1.txt);
2215 type_err(c, "error: variable '%v' redeclared",
2217 type_err(c, "info: this is where '%v' was first declared",
2218 v->where_decl, NULL, 0, NULL);
2223 Variable -> IDENTIFIER ${ {
2224 struct variable *v = var_ref(c, $1.txt);
2225 $0 = new_pos(var, $1);
2227 /* This might be a global const or a label
2228 * Allocate a var with impossible type Tnone,
2229 * which will be adjusted when we find out what it is,
2230 * or will trigger an error.
2232 v = var_decl(c, $1.txt);
2239 cast(var, $0)->var = v;
2242 ###### print exec cases
2245 struct var *v = cast(var, e);
2247 struct binding *b = v->var->name;
2248 printf("%.*s", b->name.len, b->name.txt);
2255 if (loc && loc->type == Xvar) {
2256 struct var *v = cast(var, loc);
2258 struct binding *b = v->var->name;
2259 fprintf(stderr, "%.*s", b->name.len, b->name.txt);
2261 fputs("???", stderr); // NOTEST
2263 fputs("NOTVAR", stderr); // NOTEST
2266 ###### propagate exec cases
2270 struct var *var = cast(var, prog);
2271 struct variable *v = var->var;
2273 type_err(c, "%d:BUG: no variable!!", prog, NULL, 0, NULL); // NOTEST
2274 return Tnone; // NOTEST
2277 if (v->type == Tnone && v->where_decl == prog)
2278 type_err(c, "error: variable used but not declared: %v",
2279 prog, NULL, 0, NULL);
2280 if (v->type == NULL) {
2281 if (type && !(*perr & Efail)) {
2283 v->where_set = prog;
2286 } else if (!type_compat(type, v->type, rules)) {
2287 type_err(c, "error: expected %1 but variable '%v' is %2", prog,
2288 type, rules, v->type);
2289 type_err(c, "info: this is where '%v' was set to %1", v->where_set,
2290 v->type, rules, NULL);
2292 if (!v->global || v->frame_pos < 0)
2299 ###### interp exec cases
2302 struct var *var = cast(var, e);
2303 struct variable *v = var->var;
2306 lrv = var_value(c, v);
2311 ###### ast functions
2313 static void free_var(struct var *v)
2318 ###### free exec cases
2319 case Xvar: free_var(cast(var, e)); break;
2324 Now that we have the shape of the interpreter in place we can add some
2325 complex types and connected them in to the data structures and the
2326 different phases of parse, analyse, print, interpret.
2328 Being "complex" the language will naturally have syntax to access
2329 specifics of objects of these types. These will fit into the grammar as
2330 "Terms" which are the things that are combined with various operators to
2331 form "Expression". Where a Term is formed by some operation on another
2332 Term, the subordinate Term will always come first, so for example a
2333 member of an array will be expressed as the Term for the array followed
2334 by an index in square brackets. The strict rule of using postfix
2335 operations makes precedence irrelevant within terms. To provide a place
2336 to put the grammar for each terms of each type, we will start out by
2337 introducing the "Term" grammar production, with contains at least a
2338 simple "Value" (to be explained later).
2342 Term -> Value ${ $0 = $<1; }$
2343 | Variable ${ $0 = $<1; }$
2346 Thus far the complex types we have are arrays and structs.
2350 Arrays can be declared by giving a size and a type, as `[size]type' so
2351 `freq:[26]number` declares `freq` to be an array of 26 numbers. The
2352 size can be either a literal number, or a named constant. Some day an
2353 arbitrary expression will be supported.
2355 As a formal parameter to a function, the array can be declared with a
2356 new variable as the size: `name:[size::number]string`. The `size`
2357 variable is set to the size of the array and must be a constant. As
2358 `number` is the only supported type, it can be left out:
2359 `name:[size::]string`.
2361 Arrays cannot be assigned. When pointers are introduced we will also
2362 introduce array slices which can refer to part or all of an array -
2363 the assignment syntax will create a slice. For now, an array can only
2364 ever be referenced by the name it is declared with. It is likely that
2365 a "`copy`" primitive will eventually be define which can be used to
2366 make a copy of an array with controllable recursive depth.
2368 For now we have two sorts of array, those with fixed size either because
2369 it is given as a literal number or because it is a struct member (which
2370 cannot have a runtime-changing size), and those with a size that is
2371 determined at runtime - local variables with a const size. The former
2372 have their size calculated at parse time, the latter at run time.
2374 For the latter type, the `size` field of the type is the size of a
2375 pointer, and the array is reallocated every time it comes into scope.
2377 We differentiate struct fields with a const size from local variables
2378 with a const size by whether they are prepared at parse time or not.
2380 ###### type union fields
2383 int unspec; // size is unspecified - vsize must be set.
2386 struct variable *vsize;
2387 struct type *member;
2390 ###### value union fields
2391 void *array; // used if not static_size
2393 ###### value functions
2395 static int array_prepare_type(struct parse_context *c, struct type *type,
2398 struct value *vsize;
2400 if (type->array.static_size)
2401 return 1; // UNTESTED
2402 if (type->array.unspec && parse_time)
2403 return 1; // UNTESTED
2404 if (parse_time && type->array.vsize && !type->array.vsize->global)
2405 return 1; // UNTESTED
2407 if (type->array.vsize) {
2408 vsize = var_value(c, type->array.vsize);
2410 return 1; // UNTESTED
2412 mpz_tdiv_q(q, mpq_numref(vsize->num), mpq_denref(vsize->num));
2413 type->array.size = mpz_get_si(q);
2418 if (type->array.member->size <= 0)
2419 return 0; // UNTESTED
2421 type->array.static_size = 1;
2422 type->size = type->array.size * type->array.member->size;
2423 type->align = type->array.member->align;
2428 static void array_init(struct type *type, struct value *val)
2431 void *ptr = val->ptr;
2435 if (!type->array.static_size) {
2436 val->array = calloc(type->array.size,
2437 type->array.member->size);
2440 for (i = 0; i < type->array.size; i++) {
2442 v = (void*)ptr + i * type->array.member->size;
2443 val_init(type->array.member, v);
2447 static void array_free(struct type *type, struct value *val)
2450 void *ptr = val->ptr;
2452 if (!type->array.static_size)
2454 for (i = 0; i < type->array.size; i++) {
2456 v = (void*)ptr + i * type->array.member->size;
2457 free_value(type->array.member, v);
2459 if (!type->array.static_size)
2463 static int array_compat(struct type *require, struct type *have,
2464 enum val_rules rules)
2466 if (have->compat != require->compat)
2468 /* Both are arrays, so we can look at details */
2469 if (!type_compat(require->array.member, have->array.member, 0))
2471 if (have->array.unspec && require->array.unspec &&
2472 have->array.size != require->array.size)
2474 if (have->array.unspec || require->array.unspec)
2476 if (require->array.vsize == NULL && have->array.vsize == NULL)
2477 return require->array.size == have->array.size;
2479 return require->array.vsize == have->array.vsize;
2482 static void array_print_type(struct type *type, FILE *f)
2485 if (type->array.vsize) {
2486 struct binding *b = type->array.vsize->name;
2487 fprintf(f, "%.*s%s]", b->name.len, b->name.txt,
2488 type->array.unspec ? "::" : "");
2489 } else if (type->array.size)
2490 fprintf(f, "%d]", type->array.size);
2493 type_print(type->array.member, f);
2496 static struct type array_prototype = {
2498 .prepare_type = array_prepare_type,
2499 .print_type = array_print_type,
2500 .compat = array_compat,
2502 .size = sizeof(void*),
2503 .align = sizeof(void*),
2506 ###### declare terminals
2511 | [ NUMBER ] Type ${ {
2517 if (number_parse(num, tail, $2.txt) == 0)
2518 tok_err(c, "error: unrecognised number", &$2);
2520 tok_err(c, "error: unsupported number suffix", &$2);
2523 elements = mpz_get_ui(mpq_numref(num));
2524 if (mpz_cmp_ui(mpq_denref(num), 1) != 0) {
2525 tok_err(c, "error: array size must be an integer",
2527 } else if (mpz_cmp_ui(mpq_numref(num), 1UL << 30) >= 0)
2528 tok_err(c, "error: array size is too large",
2533 $0 = t = add_anon_type(c, &array_prototype, "array[%d]", elements );
2534 t->array.size = elements;
2535 t->array.member = $<4;
2536 t->array.vsize = NULL;
2539 | [ IDENTIFIER ] Type ${ {
2540 struct variable *v = var_ref(c, $2.txt);
2543 tok_err(c, "error: name undeclared", &$2);
2544 else if (!v->constant)
2545 tok_err(c, "error: array size must be a constant", &$2);
2547 $0 = add_anon_type(c, &array_prototype, "array[%.*s]", $2.txt.len, $2.txt.txt);
2548 $0->array.member = $<4;
2550 $0->array.vsize = v;
2553 ###### formal type grammar
2556 $0 = add_anon_type(c, &array_prototype, "array[]");
2557 $0->array.member = $<Type;
2559 $0->array.unspec = 1;
2560 $0->array.vsize = NULL;
2568 | Term [ Expression ] ${ {
2569 struct binode *b = new(binode);
2577 struct binode *b = new(binode);
2583 ###### print binode cases
2585 print_exec(b->left, -1, bracket);
2587 print_exec(b->right, -1, bracket);
2592 print_exec(b->left, -1, bracket);
2596 ###### propagate binode cases
2598 /* left must be an array, right must be a number,
2599 * result is the member type of the array
2601 propagate_types(b->right, c, perr_local, Tnum, 0);
2602 t = propagate_types(b->left, c, perr, NULL, 0);
2603 if (!t || t->compat != array_compat) {
2604 type_err(c, "error: %1 cannot be indexed", prog, t, 0, NULL);
2607 if (!type_compat(type, t->array.member, rules)) {
2608 type_err(c, "error: have %1 but need %2", prog,
2609 t->array.member, rules, type);
2611 return t->array.member;
2616 /* left must be an array, result is a number
2618 t = propagate_types(b->left, c, perr, NULL, 0);
2619 if (!t || t->compat != array_compat) {
2620 type_err(c, "error: %1 cannot provide length", prog, t, 0, NULL);
2623 if (!type_compat(type, Tnum, rules))
2624 type_err(c, "error: have %1 but need %2", prog,
2629 ###### interp binode cases
2635 lleft = linterp_exec(c, b->left, <ype);
2636 right = interp_exec(c, b->right, &rtype);
2638 mpz_tdiv_q(q, mpq_numref(right.num), mpq_denref(right.num));
2642 if (ltype->array.static_size)
2645 ptr = *(void**)lleft;
2646 rvtype = ltype->array.member;
2647 if (i >= 0 && i < ltype->array.size)
2648 lrv = ptr + i * rvtype->size;
2650 val_init(ltype->array.member, &rv); // UNSAFE
2655 lleft = linterp_exec(c, b->left, <ype);
2656 mpq_set_ui(rv.num, ltype->array.size, 1);
2664 A `struct` is a data-type that contains one or more other data-types.
2665 It differs from an array in that each member can be of a different
2666 type, and they are accessed by name rather than by number. Thus you
2667 cannot choose an element by calculation, you need to know what you
2670 The language makes no promises about how a given structure will be
2671 stored in memory - it is free to rearrange fields to suit whatever
2672 criteria seems important.
2674 Structs are declared separately from program code - they cannot be
2675 declared in-line in a variable declaration like arrays can. A struct
2676 is given a name and this name is used to identify the type - the name
2677 is not prefixed by the word `struct` as it would be in C.
2679 Structs are only treated as the same if they have the same name.
2680 Simply having the same fields in the same order is not enough. This
2681 might change once we can create structure initializers from a list of
2684 Each component datum is identified much like a variable is declared,
2685 with a name, one or two colons, and a type. The type cannot be omitted
2686 as there is no opportunity to deduce the type from usage. An initial
2687 value can be given following an equals sign, so
2689 ##### Example: a struct type
2695 would declare a type called "complex" which has two number fields,
2696 each initialised to zero.
2698 Struct will need to be declared separately from the code that uses
2699 them, so we will need to be able to print out the declaration of a
2700 struct when reprinting the whole program. So a `print_type_decl` type
2701 function will be needed.
2703 ###### type union fields
2712 } *fields; // This is created when field_list is analysed.
2714 struct fieldlist *prev;
2717 } *field_list; // This is created during parsing
2720 ###### type functions
2721 void (*print_type_decl)(struct type *type, FILE *f);
2722 struct type *(*fieldref)(struct type *t, struct parse_context *c,
2723 struct fieldref *f, struct value **vp);
2725 ###### value functions
2727 static void structure_init(struct type *type, struct value *val)
2731 for (i = 0; i < type->structure.nfields; i++) {
2733 v = (void*) val->ptr + type->structure.fields[i].offset;
2734 if (type->structure.fields[i].init)
2735 dup_value(type->structure.fields[i].type,
2736 type->structure.fields[i].init,
2739 val_init(type->structure.fields[i].type, v);
2743 static void structure_free(struct type *type, struct value *val)
2747 for (i = 0; i < type->structure.nfields; i++) {
2749 v = (void*)val->ptr + type->structure.fields[i].offset;
2750 free_value(type->structure.fields[i].type, v);
2754 static void free_fieldlist(struct fieldlist *f)
2758 free_fieldlist(f->prev);
2763 static void structure_free_type(struct type *t)
2766 for (i = 0; i < t->structure.nfields; i++)
2767 if (t->structure.fields[i].init) {
2768 free_value(t->structure.fields[i].type,
2769 t->structure.fields[i].init);
2771 free(t->structure.fields);
2772 free_fieldlist(t->structure.field_list);
2775 static int structure_prepare_type(struct parse_context *c,
2776 struct type *t, int parse_time)
2779 struct fieldlist *f;
2781 if (!parse_time || t->structure.fields)
2784 for (f = t->structure.field_list; f; f=f->prev) {
2788 if (f->f.type->size <= 0)
2790 if (f->f.type->prepare_type)
2791 f->f.type->prepare_type(c, f->f.type, parse_time);
2793 if (f->init == NULL)
2797 propagate_types(f->init, c, &perr, f->f.type, 0);
2798 } while (perr & Eretry);
2800 c->parse_error += 1; // NOTEST
2803 t->structure.nfields = cnt;
2804 t->structure.fields = calloc(cnt, sizeof(struct field));
2805 f = t->structure.field_list;
2807 int a = f->f.type->align;
2809 t->structure.fields[cnt] = f->f;
2810 if (t->size & (a-1))
2811 t->size = (t->size | (a-1)) + 1;
2812 t->structure.fields[cnt].offset = t->size;
2813 t->size += ((f->f.type->size - 1) | (a-1)) + 1;
2817 if (f->init && !c->parse_error) {
2818 struct value vl = interp_exec(c, f->init, NULL);
2819 t->structure.fields[cnt].init =
2820 global_alloc(c, f->f.type, NULL, &vl);
2828 static int find_struct_index(struct type *type, struct text field)
2831 for (i = 0; i < type->structure.nfields; i++)
2832 if (text_cmp(type->structure.fields[i].name, field) == 0)
2834 return IndexInvalid;
2837 static struct type *structure_fieldref(struct type *t, struct parse_context *c,
2838 struct fieldref *f, struct value **vp)
2840 if (f->index == IndexUnknown) {
2841 f->index = find_struct_index(t, f->name);
2843 type_err(c, "error: cannot find requested field in %1",
2844 f->left, t, 0, NULL);
2849 struct value *v = *vp;
2850 v = (void*)v->ptr + t->structure.fields[f->index].offset;
2853 return t->structure.fields[f->index].type;
2856 static struct type structure_prototype = {
2857 .init = structure_init,
2858 .free = structure_free,
2859 .free_type = structure_free_type,
2860 .print_type_decl = structure_print_type,
2861 .prepare_type = structure_prepare_type,
2862 .fieldref = structure_fieldref,
2875 enum { IndexUnknown = -1, IndexInvalid = -2 };
2877 ###### free exec cases
2879 free_exec(cast(fieldref, e)->left);
2883 ###### declare terminals
2888 | Term . IDENTIFIER ${ {
2889 struct fieldref *fr = new_pos(fieldref, $2);
2892 fr->index = IndexUnknown;
2896 ###### print exec cases
2900 struct fieldref *f = cast(fieldref, e);
2901 print_exec(f->left, -1, bracket);
2902 printf(".%.*s", f->name.len, f->name.txt);
2906 ###### propagate exec cases
2910 struct fieldref *f = cast(fieldref, prog);
2911 struct type *st = propagate_types(f->left, c, perr, NULL, 0);
2913 if (!st || !st->fieldref)
2914 type_err(c, "error: field reference on %1 is not supported",
2915 f->left, st, 0, NULL);
2917 t = st->fieldref(st, c, f, NULL);
2918 if (t && !type_compat(type, t, rules))
2919 type_err(c, "error: have %1 but need %2", prog,
2926 ###### interp exec cases
2929 struct fieldref *f = cast(fieldref, e);
2931 struct value *lleft = linterp_exec(c, f->left, <ype);
2933 rvtype = ltype->fieldref(ltype, c, f, &lrv);
2937 ###### top level grammar
2939 StructName -> IDENTIFIER ${ {
2940 struct type *t = find_type(c, $ID.txt);
2942 if (t && t->size >= 0) {
2943 tok_err(c, "error: type already declared", &$ID);
2944 tok_err(c, "info: this is location of declartion", &t->first_use);
2948 t = add_type(c, $ID.txt, NULL);
2953 DeclareStruct -> struct StructName FieldBlock Newlines ${ {
2954 struct type *t = $<SN;
2955 struct type tmp = *t;
2957 *t = structure_prototype;
2960 t->first_use = tmp.first_use;
2962 t->structure.field_list = $<FB;
2966 FieldBlock -> { IN OptNL FieldLines OUT OptNL } ${ $0 = $<FL; }$
2967 | { SimpleFieldList } ${ $0 = $<SFL; }$
2968 | IN OptNL FieldLines OUT ${ $0 = $<FL; }$
2969 | SimpleFieldList EOL ${ $0 = $<SFL; }$
2971 FieldLines -> SimpleFieldList Newlines ${ $0 = $<SFL; }$
2972 | FieldLines SimpleFieldList Newlines ${
2977 SimpleFieldList -> Field ${ $0 = $<F; }$
2978 | SimpleFieldList ; Field ${
2982 | SimpleFieldList ; ${
2985 | ERROR ${ tok_err(c, "Syntax error in struct field", &$1); }$
2987 Field -> IDENTIFIER : Type = Expression ${ {
2988 $0 = calloc(1, sizeof(struct fieldlist));
2989 $0->f.name = $ID.txt;
2990 $0->f.type = $<Type;
2994 | IDENTIFIER : Type ${
2995 $0 = calloc(1, sizeof(struct fieldlist));
2996 $0->f.name = $ID.txt;
2997 $0->f.type = $<Type;
3000 ###### forward decls
3001 static void structure_print_type(struct type *t, FILE *f);
3003 ###### value functions
3004 static void structure_print_type(struct type *t, FILE *f)
3008 fprintf(f, "struct %.*s\n", t->name.len, t->name.txt);
3010 for (i = 0; i < t->structure.nfields; i++) {
3011 struct field *fl = t->structure.fields + i;
3012 fprintf(f, " %.*s : ", fl->name.len, fl->name.txt);
3013 type_print(fl->type, f);
3014 if (fl->type->print && fl->init) {
3016 if (fl->type == Tstr)
3018 print_value(fl->type, fl->init, f);
3019 if (fl->type == Tstr)
3026 ###### print type decls
3031 while (target != 0) {
3033 for (t = context.typelist; t ; t=t->next)
3034 if (!t->anon && t->print_type_decl &&
3044 t->print_type_decl(t, stdout);
3052 References, or pointers, are values that refer to another value. They
3053 can only refer to a `struct`, though as a struct can embed anything they
3054 can effectively refer to anything.
3056 References are potentially dangerous as they might refer to some
3057 variable which no longer exists - either because a stack frame
3058 containing it has been discarded or because the value was allocated on
3059 the heap and has now been free. Ocean does not yet provide any
3060 protection against these problems. It will in due course.
3062 With references comes the opportunity and the need to explicitly
3063 allocate values on the "heap" and to free them. We currently provide
3064 fairly basic support for this.
3066 Reference make use of the `@` symbol in various ways. A type that starts
3067 with `@` is a reference to whatever follows. A reference value
3068 followed by an `@` acts as the referred value, though the `@` is often
3069 not needed. Finally, an expression that starts with `@` is a special
3070 reference related expression. Some examples might help.
3072 ##### Example: Reference examples
3079 bar.number = 23; bar.string = "hello"
3090 Obviously this is very contrived. `ref` is a reference to a `foo` which
3091 is initially set to refer to the value stored in `bar` - no extra syntax
3092 is needed to "Take the address of" `bar` - the fact that `ref` is a
3093 reference means that only the address make sense.
3095 When `ref.a` is accessed, that is whatever value is stored in `bar.a`.
3096 The same syntax is used for accessing fields both in structs and in
3097 references to structs. It would be correct to use `ref@.a`, but not
3100 `@new()` creates an object of whatever type is needed for the program
3101 to by type-correct. In future iterations of Ocean, arguments a
3102 constructor will access arguments, so the the syntax now looks like a
3103 function call. `@free` can be assigned any reference that was returned
3104 by `@new()`, and it will be freed. `@nil` is a value of whatever
3105 reference type is appropriate, and is stable and never the address of
3106 anything in the heap or on the stack. A reference can be assigned
3107 `@nil` or compared against that value.
3109 ###### declare terminals
3112 ###### type union fields
3115 struct type *referent;
3118 ###### value union fields
3121 ###### value functions
3123 static void reference_print_type(struct type *t, FILE *f)
3126 type_print(t->reference.referent, f);
3129 static int reference_cmp(struct type *tl, struct type *tr,
3130 struct value *left, struct value *right)
3132 return left->ref == right->ref ? 0 : 1;
3135 static void reference_dup(struct type *t,
3136 struct value *vold, struct value *vnew)
3138 vnew->ref = vold->ref;
3141 static void reference_free(struct type *t, struct value *v)
3143 /* Nothing to do here */
3146 static int reference_compat(struct type *require, struct type *have,
3147 enum val_rules rules)
3150 if (require->reference.referent == have)
3152 if (have->compat != require->compat)
3154 if (have->reference.referent != require->reference.referent)
3159 static int reference_test(struct type *type, struct value *val)
3161 return val->ref != NULL;
3164 static struct type *reference_fieldref(struct type *t, struct parse_context *c,
3165 struct fieldref *f, struct value **vp)
3167 struct type *rt = t->reference.referent;
3172 return rt->fieldref(rt, c, f, vp);
3174 type_err(c, "error: field reference on %1 is not supported",
3175 f->left, rt, 0, NULL);
3179 static struct type reference_prototype = {
3180 .print_type = reference_print_type,
3181 .cmp_eq = reference_cmp,
3182 .dup = reference_dup,
3183 .test = reference_test,
3184 .free = reference_free,
3185 .compat = reference_compat,
3186 .fieldref = reference_fieldref,
3187 .size = sizeof(void*),
3188 .align = sizeof(void*),
3194 struct type *t = find_type(c, $ID.txt);
3196 t = add_type(c, $ID.txt, NULL);
3199 $0 = find_anon_type(c, &reference_prototype, "@%.*s",
3200 $ID.txt.len, $ID.txt.txt);
3201 $0->reference.referent = t;
3204 ###### core functions
3205 static int text_is(struct text t, char *s)
3207 return (strlen(s) == t.len &&
3208 strncmp(s, t.txt, t.len) == 0);
3217 enum ref_func { RefNew, RefFree, RefNil } action;
3218 struct type *reftype;
3222 ###### SimpleStatement Grammar
3224 | @ IDENTIFIER = Expression ${ {
3225 struct ref *r = new_pos(ref, $ID);
3227 if (!text_is($ID.txt, "free"))
3228 tok_err(c, "error: only \"@free\" makes sense here",
3232 r->action = RefFree;
3236 ###### expression grammar
3237 | @ IDENTIFIER ( ) ${
3238 // Only 'new' valid here
3239 if (!text_is($ID.txt, "new")) {
3240 tok_err(c, "error: Only reference function is \"@new()\"",
3243 struct ref *r = new_pos(ref,$ID);
3249 // Only 'nil' valid here
3250 if (!text_is($ID.txt, "nil")) {
3251 tok_err(c, "error: Only reference value is \"@nil\"",
3254 struct ref *r = new_pos(ref,$ID);
3260 ###### print exec cases
3262 struct ref *r = cast(ref, e);
3263 switch (r->action) {
3265 printf("@new()"); break;
3267 printf("@nil"); break;
3269 do_indent(indent, "@free = ");
3270 print_exec(r->right, indent, bracket);
3276 ###### propagate exec cases
3278 struct ref *r = cast(ref, prog);
3279 switch (r->action) {
3281 if (type && type->free != reference_free) {
3282 type_err(c, "error: @new() can only be used with references, not %1",
3283 prog, type, 0, NULL);
3286 if (type && !r->reftype) {
3293 if (type && type->free != reference_free)
3294 type_err(c, "error: @nil can only be used with reference, not %1",
3295 prog, type, 0, NULL);
3296 if (type && !r->reftype) {
3303 t = propagate_types(r->right, c, perr_local, NULL, 0);
3304 if (t && t->free != reference_free)
3305 type_err(c, "error: @free can only be assigned a reference, not %1",
3314 ###### interp exec cases
3316 struct ref *r = cast(ref, e);
3317 switch (r->action) {
3320 rv.ref = calloc(1, r->reftype->reference.referent->size);
3321 rvtype = r->reftype;
3325 rvtype = r->reftype;
3328 rv = interp_exec(c, r->right, &rvtype);
3329 free_value(rvtype->reference.referent, rv.ref);
3337 ###### free exec cases
3339 struct ref *r = cast(ref, e);
3340 free_exec(r->right);
3345 ###### Expressions: dereference
3353 struct binode *b = new(binode);
3359 ###### print binode cases
3361 print_exec(b->left, -1, bracket);
3365 print_exec(b->left, -1, bracket);
3368 ###### propagate binode cases
3370 /* left must be a reference, and we return what it refers to */
3371 /* FIXME how can I pass the expected type down? */
3372 t = propagate_types(b->left, c, perr, NULL, 0);
3374 if (!t || t->free != reference_free)
3375 type_err(c, "error: Cannot dereference %1", b, t, 0, NULL);
3377 return t->reference.referent;
3381 /* left must be lval, we create reference to it */
3382 if (!type || type->free != reference_free)
3383 t = propagate_types(b->left, c, perr, type, 0); // UNTESTED
3385 t = propagate_types(b->left, c, perr,
3386 type->reference.referent, 0);
3388 t = find_anon_type(c, &reference_prototype, "@%.*s",
3389 t->name.len, t->name.txt);
3392 ###### interp binode cases
3394 left = interp_exec(c, b->left, <ype);
3396 rvtype = ltype->reference.referent;
3400 rv.ref = linterp_exec(c, b->left, &rvtype);
3401 rvtype = find_anon_type(c, &reference_prototype, "@%.*s",
3402 rvtype->name.len, rvtype->name.txt);
3408 A function is a chunk of code which can be passed parameters and can
3409 return results. Each function has a type which includes the set of
3410 parameters and the return value. As yet these types cannot be declared
3411 separately from the function itself.
3413 The parameters can be specified either in parentheses as a ';' separated
3416 ##### Example: function 1
3418 func main(av:[ac::number]string; env:[envc::number]string)
3421 or as an indented list of one parameter per line (though each line can
3422 be a ';' separated list)
3424 ##### Example: function 2
3427 argv:[argc::number]string
3428 env:[envc::number]string
3432 In the first case a return type can follow the parentheses after a colon,
3433 in the second it is given on a line starting with the word `return`.
3435 ##### Example: functions that return
3437 func add(a:number; b:number): number
3447 Rather than returning a type, the function can specify a set of local
3448 variables to return as a struct. The values of these variables when the
3449 function exits will be provided to the caller. For this the return type
3450 is replaced with a block of result declarations, either in parentheses
3451 or bracketed by `return` and `do`.
3453 ##### Example: functions returning multiple variables
3455 func to_cartesian(rho:number; theta:number):(x:number; y:number)
3468 For constructing the lists we use a `List` binode, which will be
3469 further detailed when Expression Lists are introduced.
3471 ###### type union fields
3474 struct binode *params;
3475 struct type *return_type;
3476 struct variable *scope;
3477 int inline_result; // return value is at start of 'local'
3481 ###### value union fields
3482 struct exec *function;
3484 ###### type functions
3485 void (*check_args)(struct parse_context *c, enum prop_err *perr,
3486 struct type *require, struct exec *args);
3488 ###### value functions
3490 static void function_free(struct type *type, struct value *val)
3492 free_exec(val->function);
3493 val->function = NULL;
3496 static int function_compat(struct type *require, struct type *have,
3497 enum val_rules rules)
3499 // FIXME can I do anything here yet?
3503 static struct exec *take_addr(struct exec *e)
3505 struct binode *rv = new(binode);
3511 static void function_check_args(struct parse_context *c, enum prop_err *perr,
3512 struct type *require, struct exec *args)
3514 /* This should be 'compat', but we don't have a 'tuple' type to
3515 * hold the type of 'args'
3517 struct binode *arg = cast(binode, args);
3518 struct binode *param = require->function.params;
3521 struct var *pv = cast(var, param->left);
3522 struct type *t = pv->var->type, *t2;
3524 type_err(c, "error: insufficient arguments to function.",
3525 args, NULL, 0, NULL);
3529 t2 = propagate_types(arg->left, c, perr, t, Rrefok);
3530 if (t->free == reference_free &&
3531 t->reference.referent == t2 &&
3533 arg->left = take_addr(arg->left);
3534 } else if (!(*perr & Efail) && !type_compat(t2, t, 0)) {
3535 type_err(c, "error: cannot pass rval when reference expected",
3536 arg->left, NULL, 0, NULL);
3538 param = cast(binode, param->right);
3539 arg = cast(binode, arg->right);
3542 type_err(c, "error: too many arguments to function.",
3543 args, NULL, 0, NULL);
3546 static void function_print(struct type *type, struct value *val, FILE *f)
3548 print_exec(val->function, 1, 0);
3551 static void function_print_type_decl(struct type *type, FILE *f)
3555 for (b = type->function.params; b; b = cast(binode, b->right)) {
3556 struct variable *v = cast(var, b->left)->var;
3557 fprintf(f, "%.*s%s", v->name->name.len, v->name->name.txt,
3558 v->constant ? "::" : ":");
3559 type_print(v->type, f);
3564 if (type->function.return_type != Tnone) {
3566 if (type->function.inline_result) {
3568 struct type *t = type->function.return_type;
3570 for (i = 0; i < t->structure.nfields; i++) {
3571 struct field *fl = t->structure.fields + i;
3574 fprintf(f, "%.*s:", fl->name.len, fl->name.txt);
3575 type_print(fl->type, f);
3579 type_print(type->function.return_type, f);
3584 static void function_free_type(struct type *t)
3586 free_exec(t->function.params);
3589 static struct type function_prototype = {
3590 .size = sizeof(void*),
3591 .align = sizeof(void*),
3592 .free = function_free,
3593 .compat = function_compat,
3594 .check_args = function_check_args,
3595 .print = function_print,
3596 .print_type_decl = function_print_type_decl,
3597 .free_type = function_free_type,
3600 ###### declare terminals
3610 FuncName -> IDENTIFIER ${ {
3611 struct variable *v = var_decl(c, $1.txt);
3612 struct var *e = new_pos(var, $1);
3619 v = var_ref(c, $1.txt);
3621 type_err(c, "error: function '%v' redeclared",
3623 type_err(c, "info: this is where '%v' was first declared",
3624 v->where_decl, NULL, 0, NULL);
3630 Args -> ArgsLine NEWLINE ${ $0 = $<AL; }$
3631 | Args ArgsLine NEWLINE ${ {
3632 struct binode *b = $<AL;
3633 struct binode **bp = &b;
3635 bp = (struct binode **)&(*bp)->left;
3640 ArgsLine -> ${ $0 = NULL; }$
3641 | Varlist ${ $0 = $<1; }$
3642 | Varlist ; ${ $0 = $<1; }$
3644 Varlist -> Varlist ; ArgDecl ${
3645 $0 = new_pos(binode, $2);
3658 ArgDecl -> IDENTIFIER : FormalType ${ {
3659 struct variable *v = var_decl(c, $ID.txt);
3660 $0 = new_pos(var, $ID);
3667 ##### Function calls
3669 A function call can appear either as an expression or as a statement.
3670 We use a new 'Funcall' binode type to link the function with a list of
3671 arguments, form with the 'List' nodes.
3673 We have already seen the "Term" which is how a function call can appear
3674 in an expression. To parse a function call into a statement we include
3675 it in the "SimpleStatement Grammar" which will be described later.
3681 | Term ( ExpressionList ) ${ {
3682 struct binode *b = new(binode);
3685 b->right = reorder_bilist($<EL);
3689 struct binode *b = new(binode);
3696 ###### SimpleStatement Grammar
3698 | Term ( ExpressionList ) ${ {
3699 struct binode *b = new(binode);
3702 b->right = reorder_bilist($<EL);
3706 ###### print binode cases
3709 do_indent(indent, "");
3710 print_exec(b->left, -1, bracket);
3712 for (b = cast(binode, b->right); b; b = cast(binode, b->right)) {
3715 print_exec(b->left, -1, bracket);
3725 ###### propagate binode cases
3728 /* Every arg must match formal parameter, and result
3729 * is return type of function
3731 struct binode *args = cast(binode, b->right);
3732 struct var *v = cast(var, b->left);
3734 if (!v->var->type || v->var->type->check_args == NULL) {
3735 type_err(c, "error: attempt to call a non-function.",
3736 prog, NULL, 0, NULL);
3740 v->var->type->check_args(c, perr_local, v->var->type, args);
3741 if (v->var->type->function.inline_result)
3744 return v->var->type->function.return_type;
3747 ###### interp binode cases
3750 struct var *v = cast(var, b->left);
3751 struct type *t = v->var->type;
3752 void *oldlocal = c->local;
3753 int old_size = c->local_size;
3754 void *local = calloc(1, t->function.local_size);
3755 struct value *fbody = var_value(c, v->var);
3756 struct binode *arg = cast(binode, b->right);
3757 struct binode *param = t->function.params;
3760 struct var *pv = cast(var, param->left);
3761 struct type *vtype = NULL;
3762 struct value val = interp_exec(c, arg->left, &vtype);
3764 c->local = local; c->local_size = t->function.local_size;
3765 lval = var_value(c, pv->var);
3766 c->local = oldlocal; c->local_size = old_size;
3767 memcpy(lval, &val, vtype->size);
3768 param = cast(binode, param->right);
3769 arg = cast(binode, arg->right);
3771 c->local = local; c->local_size = t->function.local_size;
3772 if (t->function.inline_result && dtype) {
3773 _interp_exec(c, fbody->function, NULL, NULL);
3774 memcpy(dest, local, dtype->size);
3775 rvtype = ret.type = NULL;
3777 rv = interp_exec(c, fbody->function, &rvtype);
3778 c->local = oldlocal; c->local_size = old_size;
3783 ## Complex executables: statements and expressions
3785 Now that we have types and values and variables and most of the basic
3786 Terms which provide access to these, we can explore the more complex
3787 code that combine all of these to get useful work done. Specifically
3788 statements and expressions.
3790 Expressions are various combinations of Terms. We will use operator
3791 precedence to ensure correct parsing. The simplest Expression is just a
3792 Term - others will follow.
3797 Expression -> Term ${ $0 = $<Term; }$
3798 ## expression grammar
3800 ### Expressions: Conditional
3802 Our first user of the `binode` will be conditional expressions, which
3803 is a bit odd as they actually have three components. That will be
3804 handled by having 2 binodes for each expression. The conditional
3805 expression is the lowest precedence operator which is why we define it
3806 first - to start the precedence list.
3808 Conditional expressions are of the form "value `if` condition `else`
3809 other_value". They associate to the right, so everything to the right
3810 of `else` is part of an else value, while only a higher-precedence to
3811 the left of `if` is the if values. Between `if` and `else` there is no
3812 room for ambiguity, so a full conditional expression is allowed in
3818 ###### declare terminals
3822 ###### expression grammar
3824 | Expression if Expression else Expression $$ifelse ${ {
3825 struct binode *b1 = new(binode);
3826 struct binode *b2 = new(binode);
3836 ###### print binode cases
3839 b2 = cast(binode, b->right);
3840 if (bracket) printf("(");
3841 print_exec(b2->left, -1, bracket);
3843 print_exec(b->left, -1, bracket);
3845 print_exec(b2->right, -1, bracket);
3846 if (bracket) printf(")");
3849 ###### propagate binode cases
3852 /* cond must be Tbool, others must match */
3853 struct binode *b2 = cast(binode, b->right);
3856 propagate_types(b->left, c, perr_local, Tbool, 0);
3857 t = propagate_types(b2->left, c, perr, type, 0);
3858 t2 = propagate_types(b2->right, c, perr, type ?: t, 0);
3862 ###### interp binode cases
3865 struct binode *b2 = cast(binode, b->right);
3866 left = interp_exec(c, b->left, <ype);
3868 rv = interp_exec(c, b2->left, &rvtype);
3870 rv = interp_exec(c, b2->right, &rvtype);
3876 We take a brief detour, now that we have expressions, to describe lists
3877 of expressions. These will be needed for function parameters and
3878 possibly other situations. They seem generic enough to introduce here
3879 to be used elsewhere.
3881 And ExpressionList will use the `List` type of `binode`, building up at
3882 the end. And place where they are used will probably call
3883 `reorder_bilist()` to get a more normal first/next arrangement.
3885 ###### declare terminals
3888 `List` execs have no implicit semantics, so they are never propagated or
3889 interpreted. The can be printed as a comma separate list, which is how
3890 they are parsed. Note they are also used for function formal parameter
3891 lists. In that case a separate function is used to print them.
3893 ###### print binode cases
3897 print_exec(b->left, -1, bracket);
3900 b = cast(binode, b->right);
3904 ###### propagate binode cases
3905 case List: abort(); // NOTEST
3906 ###### interp binode cases
3907 case List: abort(); // NOTEST
3912 ExpressionList -> ExpressionList , Expression ${
3925 ### Expressions: Boolean
3927 The next class of expressions to use the `binode` will be Boolean
3928 expressions. "`and then`" and "`or else`" are similar to `and` and `or`
3929 have same corresponding precendence. The difference is that they don't
3930 evaluate the second expression if not necessary.
3939 ###### declare terminals
3944 ###### expression grammar
3945 | Expression or Expression ${ {
3946 struct binode *b = new(binode);
3952 | Expression or else Expression ${ {
3953 struct binode *b = new(binode);
3960 | Expression and Expression ${ {
3961 struct binode *b = new(binode);
3967 | Expression and then Expression ${ {
3968 struct binode *b = new(binode);
3975 | not Expression ${ {
3976 struct binode *b = new(binode);
3982 ###### print binode cases
3984 if (bracket) printf("(");
3985 print_exec(b->left, -1, bracket);
3987 print_exec(b->right, -1, bracket);
3988 if (bracket) printf(")");
3991 if (bracket) printf("(");
3992 print_exec(b->left, -1, bracket);
3993 printf(" and then ");
3994 print_exec(b->right, -1, bracket);
3995 if (bracket) printf(")");
3998 if (bracket) printf("(");
3999 print_exec(b->left, -1, bracket);
4001 print_exec(b->right, -1, bracket);
4002 if (bracket) printf(")");
4005 if (bracket) printf("(");
4006 print_exec(b->left, -1, bracket);
4007 printf(" or else ");
4008 print_exec(b->right, -1, bracket);
4009 if (bracket) printf(")");
4012 if (bracket) printf("(");
4014 print_exec(b->right, -1, bracket);
4015 if (bracket) printf(")");
4018 ###### propagate binode cases
4024 /* both must be Tbool, result is Tbool */
4025 propagate_types(b->left, c, perr, Tbool, 0);
4026 propagate_types(b->right, c, perr, Tbool, 0);
4027 if (type && type != Tbool)
4028 type_err(c, "error: %1 operation found where %2 expected", prog,
4033 ###### interp binode cases
4035 rv = interp_exec(c, b->left, &rvtype);
4036 right = interp_exec(c, b->right, &rtype);
4037 rv.bool = rv.bool && right.bool;
4040 rv = interp_exec(c, b->left, &rvtype);
4042 rv = interp_exec(c, b->right, NULL);
4045 rv = interp_exec(c, b->left, &rvtype);
4046 right = interp_exec(c, b->right, &rtype);
4047 rv.bool = rv.bool || right.bool;
4050 rv = interp_exec(c, b->left, &rvtype);
4052 rv = interp_exec(c, b->right, NULL);
4055 rv = interp_exec(c, b->right, &rvtype);
4059 ### Expressions: Comparison
4061 Of slightly higher precedence that Boolean expressions are Comparisons.
4062 A comparison takes arguments of any comparable type, but the two types
4065 To simplify the parsing we introduce an `eop` which can record an
4066 expression operator, and the `CMPop` non-terminal will match one of them.
4073 ###### ast functions
4074 static void free_eop(struct eop *e)
4088 ###### declare terminals
4089 $LEFT < > <= >= == != CMPop
4091 ###### expression grammar
4092 | Expression CMPop Expression ${ {
4093 struct binode *b = new(binode);
4103 CMPop -> < ${ $0.op = Less; }$
4104 | > ${ $0.op = Gtr; }$
4105 | <= ${ $0.op = LessEq; }$
4106 | >= ${ $0.op = GtrEq; }$
4107 | == ${ $0.op = Eql; }$
4108 | != ${ $0.op = NEql; }$
4110 ###### print binode cases
4118 if (bracket) printf("(");
4119 print_exec(b->left, -1, bracket);
4121 case Less: printf(" < "); break;
4122 case LessEq: printf(" <= "); break;
4123 case Gtr: printf(" > "); break;
4124 case GtrEq: printf(" >= "); break;
4125 case Eql: printf(" == "); break;
4126 case NEql: printf(" != "); break;
4127 default: abort(); // NOTEST
4129 print_exec(b->right, -1, bracket);
4130 if (bracket) printf(")");
4133 ###### propagate binode cases
4140 /* Both must match but not be labels, result is Tbool */
4141 t = propagate_types(b->left, c, perr, NULL, 0);
4143 propagate_types(b->right, c, perr, t, 0);
4145 t = propagate_types(b->right, c, perr, NULL, 0); // NOTEST
4147 t = propagate_types(b->left, c, perr, t, 0); // NOTEST
4149 if (!type_compat(type, Tbool, 0))
4150 type_err(c, "error: Comparison returns %1 but %2 expected", prog,
4151 Tbool, rules, type);
4155 ###### interp binode cases
4164 left = interp_exec(c, b->left, <ype);
4165 right = interp_exec(c, b->right, &rtype);
4166 cmp = value_cmp(ltype, rtype, &left, &right);
4169 case Less: rv.bool = cmp < 0; break;
4170 case LessEq: rv.bool = cmp <= 0; break;
4171 case Gtr: rv.bool = cmp > 0; break;
4172 case GtrEq: rv.bool = cmp >= 0; break;
4173 case Eql: rv.bool = cmp == 0; break;
4174 case NEql: rv.bool = cmp != 0; break;
4175 default: rv.bool = 0; break; // NOTEST
4180 ### Expressions: Arithmetic etc.
4182 The remaining expressions with the highest precedence are arithmetic,
4183 string concatenation, string conversion, and testing. String concatenation
4184 (`++`) has the same precedence as multiplication and division, but lower
4187 Testing comes in two forms. A single question mark (`?`) is a uniary
4188 operator which converts come types into Boolean. The general meaning is
4189 "is this a value value" and there will be more uses as the language
4190 develops. A double questionmark (`??`) is a binary operator (Choose),
4191 with same precedence as multiplication, which returns the LHS if it
4192 tests successfully, else returns the RHS.
4194 String conversion is a temporary feature until I get a better type
4195 system. `$` is a prefix operator which expects a string and returns
4198 `+` and `-` are both infix and prefix operations (where they are
4199 absolute value and negation). These have different operator names.
4201 We also have a 'Bracket' operator which records where parentheses were
4202 found. This makes it easy to reproduce these when printing. Possibly I
4203 should only insert brackets were needed for precedence. Putting
4204 parentheses around an expression converts it into a Term,
4210 Absolute, Negate, Test,
4214 ###### declare terminals
4216 $LEFT * / % ++ ?? Top
4220 ###### expression grammar
4221 | Expression Eop Expression ${ {
4222 struct binode *b = new(binode);
4229 | Expression Top Expression ${ {
4230 struct binode *b = new(binode);
4237 | Uop Expression ${ {
4238 struct binode *b = new(binode);
4246 | ( Expression ) ${ {
4247 struct binode *b = new_pos(binode, $1);
4256 Eop -> + ${ $0.op = Plus; }$
4257 | - ${ $0.op = Minus; }$
4259 Uop -> + ${ $0.op = Absolute; }$
4260 | - ${ $0.op = Negate; }$
4261 | $ ${ $0.op = StringConv; }$
4262 | ? ${ $0.op = Test; }$
4264 Top -> * ${ $0.op = Times; }$
4265 | / ${ $0.op = Divide; }$
4266 | % ${ $0.op = Rem; }$
4267 | ++ ${ $0.op = Concat; }$
4268 | ?? ${ $0.op = Choose; }$
4270 ###### print binode cases
4278 if (bracket) printf("(");
4279 print_exec(b->left, indent, bracket);
4281 case Plus: fputs(" + ", stdout); break;
4282 case Minus: fputs(" - ", stdout); break;
4283 case Times: fputs(" * ", stdout); break;
4284 case Divide: fputs(" / ", stdout); break;
4285 case Rem: fputs(" % ", stdout); break;
4286 case Concat: fputs(" ++ ", stdout); break;
4287 case Choose: fputs(" ?? ", stdout); break;
4288 default: abort(); // NOTEST
4290 print_exec(b->right, indent, bracket);
4291 if (bracket) printf(")");
4297 if (bracket) printf("(");
4299 case Absolute: fputs("+", stdout); break;
4300 case Negate: fputs("-", stdout); break;
4301 case StringConv: fputs("$", stdout); break;
4302 case Test: fputs("?", stdout); break;
4303 default: abort(); // NOTEST
4305 print_exec(b->right, indent, bracket);
4306 if (bracket) printf(")");
4310 print_exec(b->right, indent, bracket);
4314 ###### propagate binode cases
4320 /* both must be numbers, result is Tnum */
4323 /* as propagate_types ignores a NULL,
4324 * unary ops fit here too */
4325 propagate_types(b->left, c, perr, Tnum, 0);
4326 propagate_types(b->right, c, perr, Tnum, 0);
4327 if (!type_compat(type, Tnum, 0))
4328 type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
4334 /* both must be Tstr, result is Tstr */
4335 propagate_types(b->left, c, perr, Tstr, 0);
4336 propagate_types(b->right, c, perr, Tstr, 0);
4337 if (!type_compat(type, Tstr, 0))
4338 type_err(c, "error: Concat returns %1 but %2 expected", prog,
4344 /* op must be string, result is number */
4345 propagate_types(b->left, c, perr, Tstr, 0);
4346 if (!type_compat(type, Tnum, 0))
4348 "error: Can only convert string to number, not %1",
4349 prog, type, 0, NULL);
4354 /* LHS must support ->test, result is Tbool */
4355 t = propagate_types(b->right, c, perr, NULL, 0);
4357 type_err(c, "error: '?' requires a testable value, not %1",
4363 /* LHS and RHS must match and are returned. Must support
4366 t = propagate_types(b->left, c, perr, type, rules);
4367 t = propagate_types(b->right, c, perr, t, rules);
4368 if (t && t->test == NULL)
4369 type_err(c, "error: \"??\" requires a testable value, not %1",
4375 return propagate_types(b->right, c, perr, type, rules);
4377 ###### interp binode cases
4380 rv = interp_exec(c, b->left, &rvtype);
4381 right = interp_exec(c, b->right, &rtype);
4382 mpq_add(rv.num, rv.num, right.num);
4385 rv = interp_exec(c, b->left, &rvtype);
4386 right = interp_exec(c, b->right, &rtype);
4387 mpq_sub(rv.num, rv.num, right.num);
4390 rv = interp_exec(c, b->left, &rvtype);
4391 right = interp_exec(c, b->right, &rtype);
4392 mpq_mul(rv.num, rv.num, right.num);
4395 rv = interp_exec(c, b->left, &rvtype);
4396 right = interp_exec(c, b->right, &rtype);
4397 mpq_div(rv.num, rv.num, right.num);
4402 left = interp_exec(c, b->left, <ype);
4403 right = interp_exec(c, b->right, &rtype);
4404 mpz_init(l); mpz_init(r); mpz_init(rem);
4405 mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
4406 mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
4407 mpz_tdiv_r(rem, l, r);
4408 val_init(Tnum, &rv);
4409 mpq_set_z(rv.num, rem);
4410 mpz_clear(r); mpz_clear(l); mpz_clear(rem);
4415 rv = interp_exec(c, b->right, &rvtype);
4416 mpq_neg(rv.num, rv.num);
4419 rv = interp_exec(c, b->right, &rvtype);
4420 mpq_abs(rv.num, rv.num);
4423 rv = interp_exec(c, b->right, &rvtype);
4426 left = interp_exec(c, b->left, <ype);
4427 right = interp_exec(c, b->right, &rtype);
4429 rv.str = text_join(left.str, right.str);
4432 right = interp_exec(c, b->right, &rvtype);
4436 struct text tx = right.str;
4439 if (tx.txt[0] == '-') {
4444 if (number_parse(rv.num, tail, tx) == 0)
4447 mpq_neg(rv.num, rv.num);
4449 printf("Unsupported suffix: %.*s\n", tx.len, tx.txt);
4453 right = interp_exec(c, b->right, &rtype);
4455 rv.bool = !!rtype->test(rtype, &right);
4458 left = interp_exec(c, b->left, <ype);
4459 if (ltype->test(ltype, &left)) {
4464 rv = interp_exec(c, b->right, &rvtype);
4467 ###### value functions
4469 static struct text text_join(struct text a, struct text b)
4472 rv.len = a.len + b.len;
4473 rv.txt = malloc(rv.len);
4474 memcpy(rv.txt, a.txt, a.len);
4475 memcpy(rv.txt+a.len, b.txt, b.len);
4479 ### Blocks, Statements, and Statement lists.
4481 Now that we have expressions out of the way we need to turn to
4482 statements. There are simple statements and more complex statements.
4483 Simple statements do not contain (syntactic) newlines, complex statements do.
4485 Statements often come in sequences and we have corresponding simple
4486 statement lists and complex statement lists.
4487 The former comprise only simple statements separated by semicolons.
4488 The later comprise complex statements and simple statement lists. They are
4489 separated by newlines. Thus the semicolon is only used to separate
4490 simple statements on the one line. This may be overly restrictive,
4491 but I'm not sure I ever want a complex statement to share a line with
4494 Note that a simple statement list can still use multiple lines if
4495 subsequent lines are indented, so
4497 ###### Example: wrapped simple statement list
4502 is a single simple statement list. This might allow room for
4503 confusion, so I'm not set on it yet.
4505 A simple statement list needs no extra syntax. A complex statement
4506 list has two syntactic forms. It can be enclosed in braces (much like
4507 C blocks), or it can be introduced by an indent and continue until an
4508 unindented newline (much like Python blocks). With this extra syntax
4509 it is referred to as a block.
4511 Note that a block does not have to include any newlines if it only
4512 contains simple statements. So both of:
4514 if condition: a=b; d=f
4516 if condition { a=b; print f }
4520 In either case the list is constructed from a `binode` list with
4521 `Block` as the operator. When parsing the list it is most convenient
4522 to append to the end, so a list is a list and a statement. When using
4523 the list it is more convenient to consider a list to be a statement
4524 and a list. So we need a function to re-order a list.
4525 `reorder_bilist` serves this purpose.
4527 The only stand-alone statement we introduce at this stage is `pass`
4528 which does nothing and is represented as a `NULL` pointer in a `Block`
4529 list. Other stand-alone statements will follow once the infrastructure
4532 As many statements will use binodes, we declare a binode pointer 'b' in
4533 the common header for all reductions to use.
4535 ###### Parser: reduce
4546 Block -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4547 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4548 | SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
4549 | SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
4550 | IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
4552 OpenBlock -> OpenScope { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4553 | OpenScope { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4554 | OpenScope SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
4555 | OpenScope SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
4556 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
4558 UseBlock -> { OpenScope IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4559 | { OpenScope SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4560 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
4562 ColonBlock -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4563 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4564 | : SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
4565 | : SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
4566 | : IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
4568 Statementlist -> ComplexStatements ${ $0 = reorder_bilist($<CS); }$
4570 ComplexStatements -> ComplexStatements ComplexStatement ${
4580 | ComplexStatement ${
4592 ComplexStatement -> SimpleStatements Newlines ${
4593 $0 = reorder_bilist($<SS);
4595 | SimpleStatements ; Newlines ${
4596 $0 = reorder_bilist($<SS);
4598 ## ComplexStatement Grammar
4601 SimpleStatements -> SimpleStatements ; SimpleStatement ${
4607 | SimpleStatement ${
4616 SimpleStatement -> pass ${ $0 = NULL; }$
4617 | ERROR ${ tok_err(c, "Syntax error in statement", &$1); }$
4618 ## SimpleStatement Grammar
4620 ###### print binode cases
4622 // block, one per line
4623 if (b->left == NULL)
4624 do_indent(indent, "pass\n");
4626 print_exec(b->left, indent, bracket);
4628 print_exec(b->right, indent, bracket);
4631 ###### propagate binode cases
4634 /* If any statement returns something other than Tnone
4635 * or Tbool then all such must return same type.
4636 * As each statement may be Tnone or something else,
4637 * we must always pass NULL (unknown) down, otherwise an incorrect
4638 * error might occur. We never return Tnone unless it is
4643 for (e = b; e; e = cast(binode, e->right)) {
4644 t = propagate_types(e->left, c, perr, NULL, rules);
4645 if ((rules & Rboolok) && (t == Tbool || t == Tnone))
4647 if (t == Tnone && e->right)
4648 /* Only the final statement *must* return a value
4656 type_err(c, "error: expected %1, found %2",
4657 e->left, type, rules, t);
4663 ###### interp binode cases
4665 while (rvtype == Tnone &&
4668 rv = interp_exec(c, b->left, &rvtype);
4669 b = cast(binode, b->right);
4673 ### The Print statement
4675 `print` is a simple statement that takes a comma-separated list of
4676 expressions and prints the values separated by spaces and terminated
4677 by a newline. No control of formatting is possible.
4679 `print` uses `ExpressionList` to collect the expressions and stores them
4680 on the left side of a `Print` binode unlessthere is a trailing comma
4681 when the list is stored on the `right` side and no trailing newline is
4687 ##### declare terminals
4690 ###### SimpleStatement Grammar
4692 | print ExpressionList ${
4693 $0 = b = new_pos(binode, $1);
4696 b->left = reorder_bilist($<EL);
4698 | print ExpressionList , ${ {
4699 $0 = b = new_pos(binode, $1);
4701 b->right = reorder_bilist($<EL);
4705 $0 = b = new_pos(binode, $1);
4711 ###### print binode cases
4714 do_indent(indent, "print");
4716 print_exec(b->right, -1, bracket);
4719 print_exec(b->left, -1, bracket);
4724 ###### propagate binode cases
4727 /* don't care but all must be consistent */
4729 b = cast(binode, b->left);
4731 b = cast(binode, b->right);
4733 propagate_types(b->left, c, perr_local, NULL, 0);
4734 b = cast(binode, b->right);
4738 ###### interp binode cases
4742 struct binode *b2 = cast(binode, b->left);
4744 b2 = cast(binode, b->right);
4745 for (; b2; b2 = cast(binode, b2->right)) {
4746 left = interp_exec(c, b2->left, <ype);
4747 print_value(ltype, &left, stdout);
4748 free_value(ltype, &left);
4752 if (b->right == NULL)
4758 ###### Assignment statement
4760 An assignment will assign a value to a variable, providing it hasn't
4761 been declared as a constant. The analysis phase ensures that the type
4762 will be correct so the interpreter just needs to perform the
4763 calculation. There is a form of assignment which declares a new
4764 variable as well as assigning a value. If a name is used before
4765 it is declared, it is assumed to be a global constant which are allowed to
4766 be declared at any time.
4770 Declare, DeclareRef,
4772 ###### declare terminals
4775 ###### SimpleStatement Grammar
4776 | Term = Expression ${
4777 $0 = b= new(binode);
4782 | VariableDecl = Expression ${
4783 $0 = b= new(binode);
4790 if ($1->var->where_set == NULL) {
4792 "Variable declared with no type or value: %v",
4796 $0 = b = new(binode);
4803 ###### print binode cases
4807 do_indent(indent, "");
4808 print_exec(b->left, -1, bracket);
4810 print_exec(b->right, -1, bracket);
4818 struct variable *v = cast(var, b->left)->var;
4819 do_indent(indent, "");
4820 print_exec(b->left, -1, bracket);
4821 if (cast(var, b->left)->var->constant) {
4823 if (v->explicit_type) {
4824 type_print(v->type, stdout);
4829 if (v->explicit_type) {
4830 type_print(v->type, stdout);
4836 print_exec(b->right, -1, bracket);
4843 ###### propagate binode cases
4849 /* Both must match, or left may be ref and right an lval
4850 * Type must support 'dup',
4851 * For Assign, left must not be constant.
4854 *perr &= ~(Erval | Econst);
4855 t = propagate_types(b->left, c, perr, NULL, 0);
4860 struct type *t2 = propagate_types(b->right, c, perr_local,
4862 if (!t2 || t2 == t || (*perr_local & Efail))
4863 ; // No more effort needed
4864 else if (t->free == reference_free &&
4865 t->reference.referent == t2 &&
4866 !(*perr_local & Erval)) {
4867 if (b->op == Assign)
4869 if (b->op == Declare)
4872 else if (t->free == reference_free &&
4873 t->reference.referent == t2 &&
4874 (*perr_local & Erval))
4875 type_err(c, "error: Cannot assign an rval to a reference.",
4878 t = propagate_types(b->right, c, perr_local, NULL, 0);
4880 propagate_types(b->left, c, perr, t, 0);
4883 type_err(c, "error: cannot assign to an rval", b,
4885 else if ((b->op == Assign || b->op == AssignRef) && (*perr & Econst)) {
4886 type_err(c, "error: Cannot assign to a constant: %v",
4887 b->left, NULL, 0, NULL);
4888 if (b->left->type == Xvar) {
4889 struct var *var = cast(var, b->left);
4890 struct variable *v = var->var;
4891 type_err(c, "info: name was defined as a constant here",
4892 v->where_decl, NULL, 0, NULL);
4895 if (t && t->dup == NULL && !(*perr_local & Emaycopy))
4896 type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
4897 if (b->left->type == Xvar && (*perr_local & Efail))
4898 type_err(c, "info: variable '%v' was set as %1 here.",
4899 cast(var, b->left)->var->where_set, t, rules, NULL);
4904 ###### interp binode cases
4908 lleft = linterp_exec(c, b->left, <ype);
4910 // FIXME lleft==NULL probably means illegal array ref
4911 // should that cause a runtime error
4913 else if (b->op == AssignRef)
4914 lleft->ref = linterp_exec(c, b->right, &rtype);
4916 dinterp_exec(c, b->right, lleft, ltype, 1);
4923 struct variable *v = cast(var, b->left)->var;
4926 val = var_value(c, v);
4927 if (v->type->prepare_type)
4928 v->type->prepare_type(c, v->type, 0);
4930 val_init(v->type, val);
4931 else if (b->op == DeclareRef)
4932 val->ref = linterp_exec(c, b->right, &rtype);
4934 dinterp_exec(c, b->right, val, v->type, 0);
4938 ### The `use` statement
4940 The `use` statement is the last "simple" statement. It is needed when a
4941 statement block can return a value. This includes the body of a
4942 function which has a return type, and the "condition" code blocks in
4943 `if`, `while`, and `switch` statements.
4948 ###### declare terminals
4951 ###### SimpleStatement Grammar
4953 $0 = b = new_pos(binode, $1);
4958 ###### print binode cases
4961 do_indent(indent, "use ");
4962 print_exec(b->right, -1, bracket);
4967 ###### propagate binode cases
4970 /* result matches value */
4971 return propagate_types(b->right, c, perr, type, 0);
4973 ###### interp binode cases
4976 rv = interp_exec(c, b->right, &rvtype);
4979 ### The Conditional Statement
4981 This is the biggy and currently the only complex statement. This
4982 subsumes `if`, `while`, `do/while`, `switch`, and some parts of `for`.
4983 It is comprised of a number of parts, all of which are optional though
4984 set combinations apply. Each part is (usually) a key word (`then` is
4985 sometimes optional) followed by either an expression or a code block,
4986 except the `casepart` which is a "key word and an expression" followed
4987 by a code block. The code-block option is valid for all parts and,
4988 where an expression is also allowed, the code block can use the `use`
4989 statement to report a value. If the code block does not report a value
4990 the effect is similar to reporting `True`.
4992 The `else` and `case` parts, as well as `then` when combined with
4993 `if`, can contain a `use` statement which will apply to some
4994 containing conditional statement. `for` parts, `do` parts and `then`
4995 parts used with `for` can never contain a `use`, except in some
4996 subordinate conditional statement.
4998 If there is a `forpart`, it is executed first, only once.
4999 If there is a `dopart`, then it is executed repeatedly providing
5000 always that the `condpart` or `cond`, if present, does not return a non-True
5001 value. `condpart` can fail to return any value if it simply executes
5002 to completion. This is treated the same as returning `True`.
5004 If there is a `thenpart` it will be executed whenever the `condpart`
5005 or `cond` returns True (or does not return any value), but this will happen
5006 *after* `dopart` (when present).
5008 If `elsepart` is present it will be executed at most once when the
5009 condition returns `False` or some value that isn't `True` and isn't
5010 matched by any `casepart`. If there are any `casepart`s, they will be
5011 executed when the condition returns a matching value.
5013 The particular sorts of values allowed in case parts has not yet been
5014 determined in the language design, so nothing is prohibited.
5016 The various blocks in this complex statement potentially provide scope
5017 for variables as described earlier. Each such block must include the
5018 "OpenScope" nonterminal before parsing the block, and must call
5019 `var_block_close()` when closing the block.
5021 The code following "`if`", "`switch`" and "`for`" does not get its own
5022 scope, but is in a scope covering the whole statement, so names
5023 declared there cannot be redeclared elsewhere. Similarly the
5024 condition following "`while`" is in a scope the covers the body
5025 ("`do`" part) of the loop, and which does not allow conditional scope
5026 extension. Code following "`then`" (both looping and non-looping),
5027 "`else`" and "`case`" each get their own local scope.
5029 The type requirements on the code block in a `whilepart` are quite
5030 unusal. It is allowed to return a value of some identifiable type, in
5031 which case the loop aborts and an appropriate `casepart` is run, or it
5032 can return a Boolean, in which case the loop either continues to the
5033 `dopart` (on `True`) or aborts and runs the `elsepart` (on `False`).
5034 This is different both from the `ifpart` code block which is expected to
5035 return a Boolean, or the `switchpart` code block which is expected to
5036 return the same type as the casepart values. The correct analysis of
5037 the type of the `whilepart` code block is the reason for the
5038 `Rboolok` flag which is passed to `propagate_types()`.
5040 The `cond_statement` cannot fit into a `binode` so a new `exec` is
5041 defined. As there are two scopes which cover multiple parts - one for
5042 the whole statement and one for "while" and "do" - and as we will use
5043 the 'struct exec' to track scopes, we actually need two new types of
5044 exec. One is a `binode` for the looping part, the rest is the
5045 `cond_statement`. The `cond_statement` will use an auxilliary `struct
5046 casepart` to track a list of case parts.
5057 struct exec *action;
5058 struct casepart *next;
5060 struct cond_statement {
5062 struct exec *forpart, *condpart, *thenpart, *elsepart;
5063 struct binode *looppart;
5064 struct casepart *casepart;
5067 ###### ast functions
5069 static void free_casepart(struct casepart *cp)
5073 free_exec(cp->value);
5074 free_exec(cp->action);
5081 static void free_cond_statement(struct cond_statement *s)
5085 free_exec(s->forpart);
5086 free_exec(s->condpart);
5087 free_exec(s->looppart);
5088 free_exec(s->thenpart);
5089 free_exec(s->elsepart);
5090 free_casepart(s->casepart);
5094 ###### free exec cases
5095 case Xcond_statement: free_cond_statement(cast(cond_statement, e)); break;
5097 ###### ComplexStatement Grammar
5098 | CondStatement ${ $0 = $<1; }$
5100 ###### declare terminals
5101 $TERM for then while do
5108 // A CondStatement must end with EOL, as does CondSuffix and
5110 // ForPart, ThenPart, SwitchPart, CasePart are non-empty and
5111 // may or may not end with EOL
5112 // WhilePart and IfPart include an appropriate Suffix
5114 // ForPart, SwitchPart, and IfPart open scopes, o we have to close
5115 // them. WhilePart opens and closes its own scope.
5116 CondStatement -> ForPart OptNL ThenPart OptNL WhilePart CondSuffix ${
5119 $0->thenpart = $<TP;
5120 $0->looppart = $<WP;
5121 var_block_close(c, CloseSequential, $0);
5123 | ForPart OptNL WhilePart CondSuffix ${
5126 $0->looppart = $<WP;
5127 var_block_close(c, CloseSequential, $0);
5129 | WhilePart CondSuffix ${
5131 $0->looppart = $<WP;
5133 | SwitchPart OptNL CasePart CondSuffix ${
5135 $0->condpart = $<SP;
5136 $CP->next = $0->casepart;
5137 $0->casepart = $<CP;
5138 var_block_close(c, CloseSequential, $0);
5140 | SwitchPart : IN OptNL CasePart CondSuffix OUT Newlines ${
5142 $0->condpart = $<SP;
5143 $CP->next = $0->casepart;
5144 $0->casepart = $<CP;
5145 var_block_close(c, CloseSequential, $0);
5147 | IfPart IfSuffix ${
5149 $0->condpart = $IP.condpart; $IP.condpart = NULL;
5150 $0->thenpart = $IP.thenpart; $IP.thenpart = NULL;
5151 // This is where we close an "if" statement
5152 var_block_close(c, CloseSequential, $0);
5155 CondSuffix -> IfSuffix ${
5158 | Newlines CasePart CondSuffix ${
5160 $CP->next = $0->casepart;
5161 $0->casepart = $<CP;
5163 | CasePart CondSuffix ${
5165 $CP->next = $0->casepart;
5166 $0->casepart = $<CP;
5169 IfSuffix -> Newlines ${ $0 = new(cond_statement); }$
5170 | Newlines ElsePart ${ $0 = $<EP; }$
5171 | ElsePart ${$0 = $<EP; }$
5173 ElsePart -> else OpenBlock Newlines ${
5174 $0 = new(cond_statement);
5175 $0->elsepart = $<OB;
5176 var_block_close(c, CloseElse, $0->elsepart);
5178 | else OpenScope CondStatement ${
5179 $0 = new(cond_statement);
5180 $0->elsepart = $<CS;
5181 var_block_close(c, CloseElse, $0->elsepart);
5185 CasePart -> case Expression OpenScope ColonBlock ${
5186 $0 = calloc(1,sizeof(struct casepart));
5189 var_block_close(c, CloseParallel, $0->action);
5193 // These scopes are closed in CondStatement
5194 ForPart -> for OpenBlock ${
5198 ThenPart -> then OpenBlock ${
5200 var_block_close(c, CloseSequential, $0);
5204 // This scope is closed in CondStatement
5205 WhilePart -> while UseBlock OptNL do OpenBlock ${
5210 var_block_close(c, CloseSequential, $0->right);
5211 var_block_close(c, CloseSequential, $0);
5213 | while OpenScope Expression OpenScope ColonBlock ${
5218 var_block_close(c, CloseSequential, $0->right);
5219 var_block_close(c, CloseSequential, $0);
5223 IfPart -> if UseBlock OptNL then OpenBlock ${
5226 var_block_close(c, CloseParallel, $0.thenpart);
5228 | if OpenScope Expression OpenScope ColonBlock ${
5231 var_block_close(c, CloseParallel, $0.thenpart);
5233 | if OpenScope Expression OpenScope OptNL then Block ${
5236 var_block_close(c, CloseParallel, $0.thenpart);
5240 // This scope is closed in CondStatement
5241 SwitchPart -> switch OpenScope Expression ${
5244 | switch UseBlock ${
5248 ###### print binode cases
5250 if (b->left && b->left->type == Xbinode &&
5251 cast(binode, b->left)->op == Block) {
5253 do_indent(indent, "while {\n");
5255 do_indent(indent, "while\n");
5256 print_exec(b->left, indent+1, bracket);
5258 do_indent(indent, "} do {\n");
5260 do_indent(indent, "do\n");
5261 print_exec(b->right, indent+1, bracket);
5263 do_indent(indent, "}\n");
5265 do_indent(indent, "while ");
5266 print_exec(b->left, 0, bracket);
5271 print_exec(b->right, indent+1, bracket);
5273 do_indent(indent, "}\n");
5277 ###### print exec cases
5279 case Xcond_statement:
5281 struct cond_statement *cs = cast(cond_statement, e);
5282 struct casepart *cp;
5284 do_indent(indent, "for");
5285 if (bracket) printf(" {\n"); else printf("\n");
5286 print_exec(cs->forpart, indent+1, bracket);
5289 do_indent(indent, "} then {\n");
5291 do_indent(indent, "then\n");
5292 print_exec(cs->thenpart, indent+1, bracket);
5294 if (bracket) do_indent(indent, "}\n");
5297 print_exec(cs->looppart, indent, bracket);
5301 do_indent(indent, "switch");
5303 do_indent(indent, "if");
5304 if (cs->condpart && cs->condpart->type == Xbinode &&
5305 cast(binode, cs->condpart)->op == Block) {
5310 print_exec(cs->condpart, indent+1, bracket);
5312 do_indent(indent, "}\n");
5314 do_indent(indent, "then\n");
5315 print_exec(cs->thenpart, indent+1, bracket);
5319 print_exec(cs->condpart, 0, bracket);
5325 print_exec(cs->thenpart, indent+1, bracket);
5327 do_indent(indent, "}\n");
5332 for (cp = cs->casepart; cp; cp = cp->next) {
5333 do_indent(indent, "case ");
5334 print_exec(cp->value, -1, 0);
5339 print_exec(cp->action, indent+1, bracket);
5341 do_indent(indent, "}\n");
5344 do_indent(indent, "else");
5349 print_exec(cs->elsepart, indent+1, bracket);
5351 do_indent(indent, "}\n");
5356 ###### propagate binode cases
5358 propagate_types(b->right, c, perr_local, Tnone, 0);
5359 return propagate_types(b->left, c, perr, type, rules);
5361 ###### propagate exec cases
5362 case Xcond_statement:
5364 // forpart and looppart->right must return Tnone
5365 // thenpart must return Tnone if there is a loopart,
5366 // otherwise it is like elsepart.
5368 // be bool if there is no casepart
5369 // match casepart->values if there is a switchpart
5370 // either be bool or match casepart->value if there
5372 // elsepart and casepart->action must match the return type
5373 // expected of this statement.
5374 struct cond_statement *cs = cast(cond_statement, prog);
5375 struct casepart *cp;
5377 t = propagate_types(cs->forpart, c, perr, Tnone, 0);
5380 t = propagate_types(cs->thenpart, c, perr, Tnone, 0);
5382 if (cs->casepart == NULL) {
5383 propagate_types(cs->condpart, c, perr, Tbool, 0);
5384 propagate_types(cs->looppart, c, perr, Tbool, 0);
5386 /* Condpart must match case values, with bool permitted */
5388 for (cp = cs->casepart;
5389 cp && !t; cp = cp->next)
5390 t = propagate_types(cp->value, c, perr, NULL, 0);
5391 if (!t && cs->condpart)
5392 t = propagate_types(cs->condpart, c, perr, NULL, Rboolok); // NOTEST
5393 if (!t && cs->looppart)
5394 t = propagate_types(cs->looppart, c, perr, NULL, Rboolok); // NOTEST
5395 // Now we have a type (I hope) push it down
5397 for (cp = cs->casepart; cp; cp = cp->next)
5398 propagate_types(cp->value, c, perr, t, 0);
5399 propagate_types(cs->condpart, c, perr, t, Rboolok);
5400 propagate_types(cs->looppart, c, perr, t, Rboolok);
5403 // (if)then, else, and case parts must return expected type.
5404 if (!cs->looppart && !type)
5405 type = propagate_types(cs->thenpart, c, perr, NULL, rules);
5407 type = propagate_types(cs->elsepart, c, perr, NULL, rules);
5408 for (cp = cs->casepart;
5410 cp = cp->next) // NOTEST
5411 type = propagate_types(cp->action, c, perr, NULL, rules); // NOTEST
5414 propagate_types(cs->thenpart, c, perr, type, rules);
5415 propagate_types(cs->elsepart, c, perr, type, rules);
5416 for (cp = cs->casepart; cp ; cp = cp->next)
5417 propagate_types(cp->action, c, perr, type, rules);
5423 ###### interp binode cases
5425 // This just performs one iterration of the loop
5426 rv = interp_exec(c, b->left, &rvtype);
5427 if (rvtype == Tnone ||
5428 (rvtype == Tbool && rv.bool != 0))
5429 // rvtype is Tnone or Tbool, doesn't need to be freed
5430 interp_exec(c, b->right, NULL);
5433 ###### interp exec cases
5434 case Xcond_statement:
5436 struct value v, cnd;
5437 struct type *vtype, *cndtype;
5438 struct casepart *cp;
5439 struct cond_statement *cs = cast(cond_statement, e);
5442 interp_exec(c, cs->forpart, NULL);
5444 while ((cnd = interp_exec(c, cs->looppart, &cndtype)),
5445 cndtype == Tnone || (cndtype == Tbool && cnd.bool != 0))
5446 interp_exec(c, cs->thenpart, NULL);
5448 cnd = interp_exec(c, cs->condpart, &cndtype);
5449 if ((cndtype == Tnone ||
5450 (cndtype == Tbool && cnd.bool != 0))) {
5451 // cnd is Tnone or Tbool, doesn't need to be freed
5452 rv = interp_exec(c, cs->thenpart, &rvtype);
5453 // skip else (and cases)
5457 for (cp = cs->casepart; cp; cp = cp->next) {
5458 v = interp_exec(c, cp->value, &vtype);
5459 if (value_cmp(cndtype, vtype, &v, &cnd) == 0) {
5460 free_value(vtype, &v);
5461 free_value(cndtype, &cnd);
5462 rv = interp_exec(c, cp->action, &rvtype);
5465 free_value(vtype, &v);
5467 free_value(cndtype, &cnd);
5469 rv = interp_exec(c, cs->elsepart, &rvtype);
5476 ### Top level structure
5478 All the language elements so far can be used in various places. Now
5479 it is time to clarify what those places are.
5481 At the top level of a file there will be a number of declarations.
5482 Many of the things that can be declared haven't been described yet,
5483 such as functions, procedures, imports, and probably more.
5484 For now there are two sorts of things that can appear at the top
5485 level. They are predefined constants, `struct` types, and the `main`
5486 function. While the syntax will allow the `main` function to appear
5487 multiple times, that will trigger an error if it is actually attempted.
5489 The various declarations do not return anything. They store the
5490 various declarations in the parse context.
5492 ###### Parser: grammar
5495 Ocean -> OptNL DeclarationList
5497 ## declare terminals
5505 DeclarationList -> Declaration
5506 | DeclarationList Declaration
5508 Declaration -> ERROR Newlines ${
5509 tok_err(c, // NOTEST
5510 "error: unhandled parse error", &$1);
5516 ## top level grammar
5520 ### The `const` section
5522 As well as being defined in with the code that uses them, constants can
5523 be declared at the top level. These have full-file scope, so they are
5524 always `InScope`, even before(!) they have been declared. The value of
5525 a top level constant can be given as an expression, and this is
5526 evaluated after parsing and before execution.
5528 A function call can be used to evaluate a constant, but it will not have
5529 access to any program state, once such statement becomes meaningful.
5530 e.g. arguments and filesystem will not be visible.
5532 Constants are defined in a section that starts with the reserved word
5533 `const` and then has a block with a list of assignment statements.
5534 For syntactic consistency, these must use the double-colon syntax to
5535 make it clear that they are constants. Type can also be given: if
5536 not, the type will be determined during analysis, as with other
5539 ###### parse context
5540 struct binode *constlist;
5542 ###### top level grammar
5546 DeclareConstant -> const { IN OptNL ConstList OUT OptNL } Newlines
5547 | const { SimpleConstList } Newlines
5548 | const IN OptNL ConstList OUT Newlines
5549 | const SimpleConstList Newlines
5551 ConstList -> ConstList SimpleConstLine
5554 SimpleConstList -> SimpleConstList ; Const
5558 SimpleConstLine -> SimpleConstList Newlines
5559 | ERROR Newlines ${ tok_err(c, "Syntax error in constant", &$1); }$
5562 CType -> Type ${ $0 = $<1; }$
5566 Const -> IDENTIFIER :: CType = Expression ${ {
5568 struct binode *bl, *bv;
5569 struct var *var = new_pos(var, $ID);
5571 v = var_decl(c, $ID.txt);
5573 v->where_decl = var;
5579 v = var_ref(c, $1.txt);
5580 if (v->type == Tnone) {
5581 v->where_decl = var;
5587 tok_err(c, "error: name already declared", &$1);
5588 type_err(c, "info: this is where '%v' was first declared",
5589 v->where_decl, NULL, 0, NULL);
5601 bl->left = c->constlist;
5606 ###### core functions
5607 static void resolve_consts(struct parse_context *c)
5611 enum { none, some, cannot } progress = none;
5613 c->constlist = reorder_bilist(c->constlist);
5616 for (b = cast(binode, c->constlist); b;
5617 b = cast(binode, b->right)) {
5619 struct binode *vb = cast(binode, b->left);
5620 struct var *v = cast(var, vb->left);
5621 if (v->var->frame_pos >= 0)
5625 propagate_types(vb->right, c, &perr,
5627 } while (perr & Eretry);
5629 c->parse_error += 1;
5630 else if (!(perr & Eruntime)) {
5632 struct value res = interp_exec(
5633 c, vb->right, &v->var->type);
5634 global_alloc(c, v->var->type, v->var, &res);
5636 if (progress == cannot)
5637 type_err(c, "error: const %v cannot be resolved.",
5647 progress = cannot; break;
5649 progress = none; break;
5654 ###### print const decls
5659 for (b = cast(binode, context.constlist); b;
5660 b = cast(binode, b->right)) {
5661 struct binode *vb = cast(binode, b->left);
5662 struct var *vr = cast(var, vb->left);
5663 struct variable *v = vr->var;
5669 printf(" %.*s :: ", v->name->name.len, v->name->name.txt);
5670 type_print(v->type, stdout);
5672 print_exec(vb->right, -1, 0);
5677 ###### free const decls
5678 free_binode(context.constlist);
5680 ### Function declarations
5682 The code in an Ocean program is all stored in function declarations.
5683 One of the functions must be named `main` and it must accept an array of
5684 strings as a parameter - the command line arguments.
5686 As this is the top level, several things are handled a bit differently.
5687 The function is not interpreted by `interp_exec` as that isn't passed
5688 the argument list which the program requires. Similarly type analysis
5689 is a bit more interesting at this level.
5691 ###### ast functions
5693 static struct type *handle_results(struct parse_context *c,
5694 struct binode *results)
5696 /* Create a 'struct' type from the results list, which
5697 * is a list for 'struct var'
5699 struct type *t = add_anon_type(c, &structure_prototype,
5704 for (b = results; b; b = cast(binode, b->right))
5706 t->structure.nfields = cnt;
5707 t->structure.fields = calloc(cnt, sizeof(struct field));
5709 for (b = results; b; b = cast(binode, b->right)) {
5710 struct var *v = cast(var, b->left);
5711 struct field *f = &t->structure.fields[cnt++];
5712 int a = v->var->type->align;
5713 f->name = v->var->name->name;
5714 f->type = v->var->type;
5716 f->offset = t->size;
5717 v->var->frame_pos = f->offset;
5718 t->size += ((f->type->size - 1) | (a-1)) + 1;
5721 variable_unlink_exec(v->var);
5723 free_binode(results);
5727 static struct variable *declare_function(struct parse_context *c,
5728 struct variable *name,
5729 struct binode *args,
5731 struct binode *results,
5735 struct value fn = {.function = code};
5737 var_block_close(c, CloseFunction, code);
5738 t = add_anon_type(c, &function_prototype,
5739 "func %.*s", name->name->name.len,
5740 name->name->name.txt);
5742 t->function.params = reorder_bilist(args);
5744 ret = handle_results(c, reorder_bilist(results));
5745 t->function.inline_result = 1;
5746 t->function.local_size = ret->size;
5748 t->function.return_type = ret;
5749 global_alloc(c, t, name, &fn);
5750 name->type->function.scope = c->out_scope;
5755 var_block_close(c, CloseFunction, NULL);
5757 c->out_scope = NULL;
5761 ###### declare terminals
5764 ###### top level grammar
5767 DeclareFunction -> func FuncName ( OpenScope ArgsLine ) Block Newlines ${
5768 $0 = declare_function(c, $<FN, $<Ar, Tnone, NULL, $<Bl);
5770 | func FuncName IN OpenScope Args OUT OptNL do Block Newlines ${
5771 $0 = declare_function(c, $<FN, $<Ar, Tnone, NULL, $<Bl);
5773 | func FuncName NEWLINE OpenScope OptNL do Block Newlines ${
5774 $0 = declare_function(c, $<FN, NULL, Tnone, NULL, $<Bl);
5776 | func FuncName ( OpenScope ArgsLine ) : Type Block Newlines ${
5777 $0 = declare_function(c, $<FN, $<Ar, $<Ty, NULL, $<Bl);
5779 | func FuncName ( OpenScope ArgsLine ) : ( ArgsLine ) Block Newlines ${
5780 $0 = declare_function(c, $<FN, $<AL, NULL, $<AL2, $<Bl);
5782 | func FuncName IN OpenScope Args OUT OptNL return Type Newlines do Block Newlines ${
5783 $0 = declare_function(c, $<FN, $<Ar, $<Ty, NULL, $<Bl);
5785 | func FuncName NEWLINE OpenScope return Type Newlines do Block Newlines ${
5786 $0 = declare_function(c, $<FN, NULL, $<Ty, NULL, $<Bl);
5788 | func FuncName IN OpenScope Args OUT OptNL return IN Args OUT OptNL do Block Newlines ${
5789 $0 = declare_function(c, $<FN, $<Ar, NULL, $<Ar2, $<Bl);
5791 | func FuncName NEWLINE OpenScope return IN Args OUT OptNL do Block Newlines ${
5792 $0 = declare_function(c, $<FN, NULL, NULL, $<Ar, $<Bl);
5795 ###### print func decls
5800 while (target != 0) {
5802 for (v = context.in_scope; v; v=v->in_scope)
5803 if (v->depth == 0 && v->type && v->type->check_args) {
5812 struct value *val = var_value(&context, v);
5813 printf("func %.*s", v->name->name.len, v->name->name.txt);
5814 v->type->print_type_decl(v->type, stdout);
5816 print_exec(val->function, 0, brackets);
5818 print_value(v->type, val, stdout);
5819 printf("/* frame size %d */\n", v->type->function.local_size);
5825 ###### core functions
5827 static int analyse_funcs(struct parse_context *c)
5831 for (v = c->in_scope; v; v = v->in_scope) {
5835 if (v->depth != 0 || !v->type || !v->type->check_args)
5837 ret = v->type->function.inline_result ?
5838 Tnone : v->type->function.return_type;
5839 val = var_value(c, v);
5842 propagate_types(val->function, c, &perr, ret, 0);
5843 } while (!(perr & Efail) && (perr & Eretry));
5844 if (!(perr & Efail))
5845 /* Make sure everything is still consistent */
5846 propagate_types(val->function, c, &perr, ret, 0);
5849 if (!v->type->function.inline_result &&
5850 !v->type->function.return_type->dup) {
5851 type_err(c, "error: function cannot return value of type %1",
5852 v->where_decl, v->type->function.return_type, 0, NULL);
5855 scope_finalize(c, v->type);
5860 static int analyse_main(struct type *type, struct parse_context *c)
5862 struct binode *bp = type->function.params;
5866 struct type *argv_type;
5868 argv_type = add_anon_type(c, &array_prototype, "argv");
5869 argv_type->array.member = Tstr;
5870 argv_type->array.unspec = 1;
5872 for (b = bp; b; b = cast(binode, b->right)) {
5876 propagate_types(b->left, c, &perr, argv_type, 0);
5878 default: /* invalid */ // NOTEST
5879 propagate_types(b->left, c, &perr, Tnone, 0); // NOTEST
5882 c->parse_error += 1;
5885 return !c->parse_error;
5888 static void interp_main(struct parse_context *c, int argc, char **argv)
5890 struct value *progp = NULL;
5891 struct text main_name = { "main", 4 };
5892 struct variable *mainv;
5898 mainv = var_ref(c, main_name);
5900 progp = var_value(c, mainv);
5901 if (!progp || !progp->function) {
5902 fprintf(stderr, "oceani: no main function found.\n");
5903 c->parse_error += 1;
5906 if (!analyse_main(mainv->type, c)) {
5907 fprintf(stderr, "oceani: main has wrong type.\n");
5908 c->parse_error += 1;
5911 al = mainv->type->function.params;
5913 c->local_size = mainv->type->function.local_size;
5914 c->local = calloc(1, c->local_size);
5916 struct var *v = cast(var, al->left);
5917 struct value *vl = var_value(c, v->var);
5925 t->array.size = argc;
5926 t->prepare_type(c, t, 0);
5927 array_init(v->var->type, vl);
5928 for (i = 0; i < argc; i++) {
5929 struct value *vl2 = vl->array + i * v->var->type->array.member->size;
5931 arg.str.txt = argv[i];
5932 arg.str.len = strlen(argv[i]);
5933 free_value(Tstr, vl2);
5934 dup_value(Tstr, &arg, vl2);
5938 al = cast(binode, al->right);
5940 v = interp_exec(c, progp->function, &vtype);
5941 free_value(vtype, &v);
5946 ###### ast functions
5947 void free_variable(struct variable *v)
5951 ## And now to test it out.
5953 Having a language requires having a "hello world" program. I'll
5954 provide a little more than that: a program that prints "Hello world"
5955 finds the GCD of two numbers, prints the first few elements of
5956 Fibonacci, performs a binary search for a number, and a few other
5957 things which will likely grow as the languages grows.
5959 ###### File: oceani.mk
5962 @echo "===== DEMO ====="
5963 ./oceani --section "demo: hello" oceani.mdc 55 33
5969 four ::= 2 + 2 ; five ::= 10/2
5970 const pie ::= "I like Pie";
5971 cake ::= "The cake is"
5979 func main(argv:[]string)
5980 print "Hello World, what lovely oceans you have!"
5981 print "Are there", five, "?"
5982 print pi, pie, "but", cake
5984 A := $argv[1]; B := $argv[2]
5986 /* When a variable is defined in both branches of an 'if',
5987 * and used afterwards, the variables are merged.
5993 print "Is", A, "bigger than", B,"? ", bigger
5994 /* If a variable is not used after the 'if', no
5995 * merge happens, so types can be different
5998 double:string = "yes"
5999 print A, "is more than twice", B, "?", double
6002 print "double", B, "is", double
6007 if a > 0 and then b > 0:
6013 print "GCD of", A, "and", B,"is", a
6015 print a, "is not positive, cannot calculate GCD"
6017 print b, "is not positive, cannot calculate GCD"
6022 print "Fibonacci:", f1,f2,
6023 then togo = togo - 1
6031 /* Binary search... */
6036 mid := (lo + hi) / 2
6049 print "Yay, I found", target
6051 print "Closest I found was", lo
6056 // "middle square" PRNG. Not particularly good, but one my
6057 // Dad taught me - the first one I ever heard of.
6058 for i:=1; then i = i + 1; while i < size:
6059 n := list[i-1] * list[i-1]
6060 list[i] = (n / 100) % 10 000
6062 print "Before sort:",
6063 for i:=0; then i = i + 1; while i < size:
6067 for i := 1; then i=i+1; while i < size:
6068 for j:=i-1; then j=j-1; while j >= 0:
6069 if list[j] > list[j+1]:
6073 print " After sort:",
6074 for i:=0; then i = i + 1; while i < size:
6078 if 1 == 2 then print "yes"; else print "no"
6082 bob.alive = (bob.name == "Hello")
6083 print "bob", "is" if bob.alive else "isn't", "alive"