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); // UNTESTED
1282 tok_err(c, "error: unsupported number suffix",
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; // UNTESTED
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); // NOTEST
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 if (have->array.vsize && require->array.vsize &&
2473 have->array.vsize != require->array.vsize) // UNTESTED
2474 /* sizes might not be the same */
2475 return 0; // UNTESTED
2478 if (have->array.unspec || require->array.unspec)
2479 return 1; // UNTESTED
2480 if (require->array.vsize == NULL && have->array.vsize == NULL)
2481 return require->array.size == have->array.size;
2483 return require->array.vsize == have->array.vsize; // UNTESTED
2486 static void array_print_type(struct type *type, FILE *f)
2489 if (type->array.vsize) {
2490 struct binding *b = type->array.vsize->name;
2491 fprintf(f, "%.*s%s]", b->name.len, b->name.txt,
2492 type->array.unspec ? "::" : "");
2493 } else if (type->array.size)
2494 fprintf(f, "%d]", type->array.size);
2497 type_print(type->array.member, f);
2500 static struct type array_prototype = {
2502 .prepare_type = array_prepare_type,
2503 .print_type = array_print_type,
2504 .compat = array_compat,
2506 .size = sizeof(void*),
2507 .align = sizeof(void*),
2510 ###### declare terminals
2515 | [ NUMBER ] Type ${ {
2521 if (number_parse(num, tail, $2.txt) == 0)
2522 tok_err(c, "error: unrecognised number", &$2);
2524 tok_err(c, "error: unsupported number suffix", &$2);
2527 elements = mpz_get_ui(mpq_numref(num));
2528 if (mpz_cmp_ui(mpq_denref(num), 1) != 0) {
2529 tok_err(c, "error: array size must be an integer",
2531 } else if (mpz_cmp_ui(mpq_numref(num), 1UL << 30) >= 0)
2532 tok_err(c, "error: array size is too large",
2537 $0 = t = add_anon_type(c, &array_prototype, "array[%d]", elements );
2538 t->array.size = elements;
2539 t->array.member = $<4;
2540 t->array.vsize = NULL;
2543 | [ IDENTIFIER ] Type ${ {
2544 struct variable *v = var_ref(c, $2.txt);
2547 tok_err(c, "error: name undeclared", &$2);
2548 else if (!v->constant)
2549 tok_err(c, "error: array size must be a constant", &$2);
2551 $0 = add_anon_type(c, &array_prototype, "array[%.*s]", $2.txt.len, $2.txt.txt);
2552 $0->array.member = $<4;
2554 $0->array.vsize = v;
2559 OptType -> Type ${ $0 = $<1; }$
2562 ###### formal type grammar
2564 | [ IDENTIFIER :: OptType ] Type ${ {
2565 struct variable *v = var_decl(c, $ID.txt);
2571 $0 = add_anon_type(c, &array_prototype, "array[var]");
2572 $0->array.member = $<6;
2574 $0->array.unspec = 1;
2575 $0->array.vsize = v;
2583 | Term [ Expression ] ${ {
2584 struct binode *b = new(binode);
2591 ###### print binode cases
2593 print_exec(b->left, -1, bracket);
2595 print_exec(b->right, -1, bracket);
2599 ###### propagate binode cases
2601 /* left must be an array, right must be a number,
2602 * result is the member type of the array
2604 propagate_types(b->right, c, perr_local, Tnum, 0);
2605 t = propagate_types(b->left, c, perr, NULL, 0);
2606 if (!t || t->compat != array_compat) {
2607 type_err(c, "error: %1 cannot be indexed", prog, t, 0, NULL);
2610 if (!type_compat(type, t->array.member, rules)) {
2611 type_err(c, "error: have %1 but need %2", prog,
2612 t->array.member, rules, type);
2614 return t->array.member;
2618 ###### interp binode cases
2624 lleft = linterp_exec(c, b->left, <ype);
2625 right = interp_exec(c, b->right, &rtype);
2627 mpz_tdiv_q(q, mpq_numref(right.num), mpq_denref(right.num));
2631 if (ltype->array.static_size)
2634 ptr = *(void**)lleft;
2635 rvtype = ltype->array.member;
2636 if (i >= 0 && i < ltype->array.size)
2637 lrv = ptr + i * rvtype->size;
2639 val_init(ltype->array.member, &rv); // UNSAFE
2646 A `struct` is a data-type that contains one or more other data-types.
2647 It differs from an array in that each member can be of a different
2648 type, and they are accessed by name rather than by number. Thus you
2649 cannot choose an element by calculation, you need to know what you
2652 The language makes no promises about how a given structure will be
2653 stored in memory - it is free to rearrange fields to suit whatever
2654 criteria seems important.
2656 Structs are declared separately from program code - they cannot be
2657 declared in-line in a variable declaration like arrays can. A struct
2658 is given a name and this name is used to identify the type - the name
2659 is not prefixed by the word `struct` as it would be in C.
2661 Structs are only treated as the same if they have the same name.
2662 Simply having the same fields in the same order is not enough. This
2663 might change once we can create structure initializers from a list of
2666 Each component datum is identified much like a variable is declared,
2667 with a name, one or two colons, and a type. The type cannot be omitted
2668 as there is no opportunity to deduce the type from usage. An initial
2669 value can be given following an equals sign, so
2671 ##### Example: a struct type
2677 would declare a type called "complex" which has two number fields,
2678 each initialised to zero.
2680 Struct will need to be declared separately from the code that uses
2681 them, so we will need to be able to print out the declaration of a
2682 struct when reprinting the whole program. So a `print_type_decl` type
2683 function will be needed.
2685 ###### type union fields
2694 } *fields; // This is created when field_list is analysed.
2696 struct fieldlist *prev;
2699 } *field_list; // This is created during parsing
2702 ###### type functions
2703 void (*print_type_decl)(struct type *type, FILE *f);
2704 struct type *(*fieldref)(struct type *t, struct parse_context *c,
2705 struct fieldref *f, struct value **vp);
2707 ###### value functions
2709 static void structure_init(struct type *type, struct value *val)
2713 for (i = 0; i < type->structure.nfields; i++) {
2715 v = (void*) val->ptr + type->structure.fields[i].offset;
2716 if (type->structure.fields[i].init)
2717 dup_value(type->structure.fields[i].type,
2718 type->structure.fields[i].init,
2721 val_init(type->structure.fields[i].type, v);
2725 static void structure_free(struct type *type, struct value *val)
2729 for (i = 0; i < type->structure.nfields; i++) {
2731 v = (void*)val->ptr + type->structure.fields[i].offset;
2732 free_value(type->structure.fields[i].type, v);
2736 static void free_fieldlist(struct fieldlist *f)
2740 free_fieldlist(f->prev);
2745 static void structure_free_type(struct type *t)
2748 for (i = 0; i < t->structure.nfields; i++)
2749 if (t->structure.fields[i].init) {
2750 free_value(t->structure.fields[i].type,
2751 t->structure.fields[i].init);
2753 free(t->structure.fields);
2754 free_fieldlist(t->structure.field_list);
2757 static int structure_prepare_type(struct parse_context *c,
2758 struct type *t, int parse_time)
2761 struct fieldlist *f;
2763 if (!parse_time || t->structure.fields)
2766 for (f = t->structure.field_list; f; f=f->prev) {
2770 if (f->f.type->size <= 0)
2772 if (f->f.type->prepare_type)
2773 f->f.type->prepare_type(c, f->f.type, parse_time);
2775 if (f->init == NULL)
2779 propagate_types(f->init, c, &perr, f->f.type, 0);
2780 } while (perr & Eretry);
2782 c->parse_error += 1; // NOTEST
2785 t->structure.nfields = cnt;
2786 t->structure.fields = calloc(cnt, sizeof(struct field));
2787 f = t->structure.field_list;
2789 int a = f->f.type->align;
2791 t->structure.fields[cnt] = f->f;
2792 if (t->size & (a-1))
2793 t->size = (t->size | (a-1)) + 1;
2794 t->structure.fields[cnt].offset = t->size;
2795 t->size += ((f->f.type->size - 1) | (a-1)) + 1;
2799 if (f->init && !c->parse_error) {
2800 struct value vl = interp_exec(c, f->init, NULL);
2801 t->structure.fields[cnt].init =
2802 global_alloc(c, f->f.type, NULL, &vl);
2810 static int find_struct_index(struct type *type, struct text field)
2813 for (i = 0; i < type->structure.nfields; i++)
2814 if (text_cmp(type->structure.fields[i].name, field) == 0)
2816 return IndexInvalid;
2819 static struct type *structure_fieldref(struct type *t, struct parse_context *c,
2820 struct fieldref *f, struct value **vp)
2822 if (f->index == IndexUnknown) {
2823 f->index = find_struct_index(t, f->name);
2825 type_err(c, "error: cannot find requested field in %1",
2826 f->left, t, 0, NULL);
2831 struct value *v = *vp;
2832 v = (void*)v->ptr + t->structure.fields[f->index].offset;
2835 return t->structure.fields[f->index].type;
2838 static struct type structure_prototype = {
2839 .init = structure_init,
2840 .free = structure_free,
2841 .free_type = structure_free_type,
2842 .print_type_decl = structure_print_type,
2843 .prepare_type = structure_prepare_type,
2844 .fieldref = structure_fieldref,
2857 enum { IndexUnknown = -1, IndexInvalid = -2 };
2859 ###### free exec cases
2861 free_exec(cast(fieldref, e)->left);
2865 ###### declare terminals
2870 | Term . IDENTIFIER ${ {
2871 struct fieldref *fr = new_pos(fieldref, $2);
2874 fr->index = IndexUnknown;
2878 ###### print exec cases
2882 struct fieldref *f = cast(fieldref, e);
2883 print_exec(f->left, -1, bracket);
2884 printf(".%.*s", f->name.len, f->name.txt);
2888 ###### propagate exec cases
2892 struct fieldref *f = cast(fieldref, prog);
2893 struct type *st = propagate_types(f->left, c, perr, NULL, 0);
2895 if (!st || !st->fieldref)
2896 type_err(c, "error: field reference on %1 is not supported",
2897 f->left, st, 0, NULL);
2899 t = st->fieldref(st, c, f, NULL);
2900 if (t && !type_compat(type, t, rules))
2901 type_err(c, "error: have %1 but need %2", prog,
2908 ###### interp exec cases
2911 struct fieldref *f = cast(fieldref, e);
2913 struct value *lleft = linterp_exec(c, f->left, <ype);
2915 rvtype = ltype->fieldref(ltype, c, f, &lrv);
2919 ###### top level grammar
2921 StructName -> IDENTIFIER ${ {
2922 struct type *t = find_type(c, $ID.txt);
2924 if (t && t->size >= 0) {
2925 tok_err(c, "error: type already declared", &$ID);
2926 tok_err(c, "info: this is location of declartion", &t->first_use);
2930 t = add_type(c, $ID.txt, NULL);
2935 DeclareStruct -> struct StructName FieldBlock Newlines ${ {
2936 struct type *t = $<SN;
2937 struct type tmp = *t;
2939 *t = structure_prototype;
2942 t->first_use = tmp.first_use;
2944 t->structure.field_list = $<FB;
2948 FieldBlock -> { IN OptNL FieldLines OUT OptNL } ${ $0 = $<FL; }$
2949 | { SimpleFieldList } ${ $0 = $<SFL; }$
2950 | IN OptNL FieldLines OUT ${ $0 = $<FL; }$
2951 | SimpleFieldList EOL ${ $0 = $<SFL; }$
2953 FieldLines -> SimpleFieldList Newlines ${ $0 = $<SFL; }$
2954 | FieldLines SimpleFieldList Newlines ${
2959 SimpleFieldList -> Field ${ $0 = $<F; }$
2960 | SimpleFieldList ; Field ${
2964 | SimpleFieldList ; ${
2967 | ERROR ${ tok_err(c, "Syntax error in struct field", &$1); }$
2969 Field -> IDENTIFIER : Type = Expression ${ {
2970 $0 = calloc(1, sizeof(struct fieldlist));
2971 $0->f.name = $ID.txt;
2972 $0->f.type = $<Type;
2976 | IDENTIFIER : Type ${
2977 $0 = calloc(1, sizeof(struct fieldlist));
2978 $0->f.name = $ID.txt;
2979 $0->f.type = $<Type;
2982 ###### forward decls
2983 static void structure_print_type(struct type *t, FILE *f);
2985 ###### value functions
2986 static void structure_print_type(struct type *t, FILE *f)
2990 fprintf(f, "struct %.*s\n", t->name.len, t->name.txt);
2992 for (i = 0; i < t->structure.nfields; i++) {
2993 struct field *fl = t->structure.fields + i;
2994 fprintf(f, " %.*s : ", fl->name.len, fl->name.txt);
2995 type_print(fl->type, f);
2996 if (fl->type->print && fl->init) {
2998 if (fl->type == Tstr)
2999 fprintf(f, "\""); // UNTESTED
3000 print_value(fl->type, fl->init, f);
3001 if (fl->type == Tstr)
3002 fprintf(f, "\""); // UNTESTED
3008 ###### print type decls
3013 while (target != 0) {
3015 for (t = context.typelist; t ; t=t->next)
3016 if (!t->anon && t->print_type_decl &&
3026 t->print_type_decl(t, stdout);
3034 References, or pointers, are values that refer to another value. They
3035 can only refer to a `struct`, though as a struct can embed anything they
3036 can effectively refer to anything.
3038 References are potentially dangerous as they might refer to some
3039 variable which no longer exists - either because a stack frame
3040 containing it has been discarded or because the value was allocated on
3041 the heap and has now been free. Ocean does not yet provide any
3042 protection against these problems. It will in due course.
3044 With references comes the opportunity and the need to explicitly
3045 allocate values on the "heap" and to free them. We currently provide
3046 fairly basic support for this.
3048 Reference make use of the `@` symbol in various ways. A type that starts
3049 with `@` is a reference to whatever follows. A reference value
3050 followed by an `@` acts as the referred value, though the `@` is often
3051 not needed. Finally, an expression that starts with `@` is a special
3052 reference related expression. Some examples might help.
3054 ##### Example: Reference examples
3061 bar.number = 23; bar.string = "hello"
3072 Obviously this is very contrived. `ref` is a reference to a `foo` which
3073 is initially set to refer to the value stored in `bar` - no extra syntax
3074 is needed to "Take the address of" `bar` - the fact that `ref` is a
3075 reference means that only the address make sense.
3077 When `ref.a` is accessed, that is whatever value is stored in `bar.a`.
3078 The same syntax is used for accessing fields both in structs and in
3079 references to structs. It would be correct to use `ref@.a`, but not
3082 `@new()` creates an object of whatever type is needed for the program
3083 to by type-correct. In future iterations of Ocean, arguments a
3084 constructor will access arguments, so the the syntax now looks like a
3085 function call. `@free` can be assigned any reference that was returned
3086 by `@new()`, and it will be freed. `@nil` is a value of whatever
3087 reference type is appropriate, and is stable and never the address of
3088 anything in the heap or on the stack. A reference can be assigned
3089 `@nil` or compared against that value.
3091 ###### declare terminals
3094 ###### type union fields
3097 struct type *referent;
3100 ###### value union fields
3103 ###### value functions
3105 static void reference_print_type(struct type *t, FILE *f)
3108 type_print(t->reference.referent, f);
3111 static int reference_cmp(struct type *tl, struct type *tr,
3112 struct value *left, struct value *right)
3114 return left->ref == right->ref ? 0 : 1;
3117 static void reference_dup(struct type *t,
3118 struct value *vold, struct value *vnew)
3120 vnew->ref = vold->ref;
3123 static void reference_free(struct type *t, struct value *v)
3125 /* Nothing to do here */
3128 static int reference_compat(struct type *require, struct type *have,
3129 enum val_rules rules)
3132 if (require->reference.referent == have)
3134 if (have->compat != require->compat)
3136 if (have->reference.referent != require->reference.referent)
3141 static int reference_test(struct type *type, struct value *val)
3143 return val->ref != NULL;
3146 static struct type *reference_fieldref(struct type *t, struct parse_context *c,
3147 struct fieldref *f, struct value **vp)
3149 struct type *rt = t->reference.referent;
3154 return rt->fieldref(rt, c, f, vp);
3156 type_err(c, "error: field reference on %1 is not supported",
3157 f->left, rt, 0, NULL);
3161 static struct type reference_prototype = {
3162 .print_type = reference_print_type,
3163 .cmp_eq = reference_cmp,
3164 .dup = reference_dup,
3165 .test = reference_test,
3166 .free = reference_free,
3167 .compat = reference_compat,
3168 .fieldref = reference_fieldref,
3169 .size = sizeof(void*),
3170 .align = sizeof(void*),
3176 struct type *t = find_type(c, $ID.txt);
3178 t = add_type(c, $ID.txt, NULL);
3181 $0 = find_anon_type(c, &reference_prototype, "@%.*s",
3182 $ID.txt.len, $ID.txt.txt);
3183 $0->reference.referent = t;
3186 ###### core functions
3187 static int text_is(struct text t, char *s)
3189 return (strlen(s) == t.len &&
3190 strncmp(s, t.txt, t.len) == 0);
3199 enum ref_func { RefNew, RefFree, RefNil } action;
3200 struct type *reftype;
3204 ###### SimpleStatement Grammar
3206 | @ IDENTIFIER = Expression ${ {
3207 struct ref *r = new_pos(ref, $ID);
3209 if (!text_is($ID.txt, "free"))
3210 tok_err(c, "error: only \"@free\" makes sense here",
3214 r->action = RefFree;
3218 ###### expression grammar
3219 | @ IDENTIFIER ( ) ${
3220 // Only 'new' valid here
3221 if (!text_is($ID.txt, "new")) {
3222 tok_err(c, "error: Only reference function is \"@new()\"",
3225 struct ref *r = new_pos(ref,$ID);
3231 // Only 'nil' valid here
3232 if (!text_is($ID.txt, "nil")) {
3233 tok_err(c, "error: Only reference value is \"@nil\"",
3236 struct ref *r = new_pos(ref,$ID);
3242 ###### print exec cases
3244 struct ref *r = cast(ref, e);
3245 switch (r->action) {
3247 printf("@new()"); break;
3249 printf("@nil"); break;
3251 do_indent(indent, "@free = ");
3252 print_exec(r->right, indent, bracket);
3258 ###### propagate exec cases
3260 struct ref *r = cast(ref, prog);
3261 switch (r->action) {
3263 if (type && type->free != reference_free) {
3264 type_err(c, "error: @new() can only be used with references, not %1",
3265 prog, type, 0, NULL);
3268 if (type && !r->reftype) {
3275 if (type && type->free != reference_free)
3276 type_err(c, "error: @nil can only be used with reference, not %1",
3277 prog, type, 0, NULL);
3278 if (type && !r->reftype) {
3285 t = propagate_types(r->right, c, perr_local, NULL, 0);
3286 if (t && t->free != reference_free)
3287 type_err(c, "error: @free can only be assigned a reference, not %1",
3296 ###### interp exec cases
3298 struct ref *r = cast(ref, e);
3299 switch (r->action) {
3302 rv.ref = calloc(1, r->reftype->reference.referent->size);
3303 rvtype = r->reftype;
3307 rvtype = r->reftype;
3310 rv = interp_exec(c, r->right, &rvtype);
3311 free_value(rvtype->reference.referent, rv.ref);
3319 ###### free exec cases
3321 struct ref *r = cast(ref, e);
3322 free_exec(r->right);
3327 ###### Expressions: dereference
3335 struct binode *b = new(binode);
3341 ###### print binode cases
3343 print_exec(b->left, -1, bracket);
3347 ###### propagate binode cases
3349 /* left must be a reference, and we return what it refers to */
3350 /* FIXME how can I pass the expected type down? */
3351 t = propagate_types(b->left, c, perr, NULL, 0);
3353 if (!t || t->free != reference_free)
3354 type_err(c, "error: Cannot dereference %1", b, t, 0, NULL);
3356 return t->reference.referent;
3359 ###### interp binode cases
3361 left = interp_exec(c, b->left, <ype);
3363 rvtype = ltype->reference.referent;
3370 A function is a chunk of code which can be passed parameters and can
3371 return results. Each function has a type which includes the set of
3372 parameters and the return value. As yet these types cannot be declared
3373 separately from the function itself.
3375 The parameters can be specified either in parentheses as a ';' separated
3378 ##### Example: function 1
3380 func main(av:[ac::number]string; env:[envc::number]string)
3383 or as an indented list of one parameter per line (though each line can
3384 be a ';' separated list)
3386 ##### Example: function 2
3389 argv:[argc::number]string
3390 env:[envc::number]string
3394 In the first case a return type can follow the parentheses after a colon,
3395 in the second it is given on a line starting with the word `return`.
3397 ##### Example: functions that return
3399 func add(a:number; b:number): number
3409 Rather than returning a type, the function can specify a set of local
3410 variables to return as a struct. The values of these variables when the
3411 function exits will be provided to the caller. For this the return type
3412 is replaced with a block of result declarations, either in parentheses
3413 or bracketed by `return` and `do`.
3415 ##### Example: functions returning multiple variables
3417 func to_cartesian(rho:number; theta:number):(x:number; y:number)
3430 For constructing the lists we use a `List` binode, which will be
3431 further detailed when Expression Lists are introduced.
3433 ###### type union fields
3436 struct binode *params;
3437 struct type *return_type;
3438 struct variable *scope;
3439 int inline_result; // return value is at start of 'local'
3443 ###### value union fields
3444 struct exec *function;
3446 ###### type functions
3447 void (*check_args)(struct parse_context *c, enum prop_err *perr,
3448 struct type *require, struct exec *args);
3450 ###### value functions
3452 static void function_free(struct type *type, struct value *val)
3454 free_exec(val->function);
3455 val->function = NULL;
3458 static int function_compat(struct type *require, struct type *have,
3459 enum val_rules rules)
3461 // FIXME can I do anything here yet?
3465 static void function_check_args(struct parse_context *c, enum prop_err *perr,
3466 struct type *require, struct exec *args)
3468 /* This should be 'compat', but we don't have a 'tuple' type to
3469 * hold the type of 'args'
3471 struct binode *arg = cast(binode, args);
3472 struct binode *param = require->function.params;
3475 struct var *pv = cast(var, param->left);
3477 type_err(c, "error: insufficient arguments to function.",
3478 args, NULL, 0, NULL);
3482 propagate_types(arg->left, c, perr, pv->var->type, 0);
3483 param = cast(binode, param->right);
3484 arg = cast(binode, arg->right);
3487 type_err(c, "error: too many arguments to function.",
3488 args, NULL, 0, NULL);
3491 static void function_print(struct type *type, struct value *val, FILE *f)
3493 print_exec(val->function, 1, 0);
3496 static void function_print_type_decl(struct type *type, FILE *f)
3500 for (b = type->function.params; b; b = cast(binode, b->right)) {
3501 struct variable *v = cast(var, b->left)->var;
3502 fprintf(f, "%.*s%s", v->name->name.len, v->name->name.txt,
3503 v->constant ? "::" : ":");
3504 type_print(v->type, f);
3509 if (type->function.return_type != Tnone) {
3511 if (type->function.inline_result) {
3513 struct type *t = type->function.return_type;
3515 for (i = 0; i < t->structure.nfields; i++) {
3516 struct field *fl = t->structure.fields + i;
3519 fprintf(f, "%.*s:", fl->name.len, fl->name.txt);
3520 type_print(fl->type, f);
3524 type_print(type->function.return_type, f);
3529 static void function_free_type(struct type *t)
3531 free_exec(t->function.params);
3534 static struct type function_prototype = {
3535 .size = sizeof(void*),
3536 .align = sizeof(void*),
3537 .free = function_free,
3538 .compat = function_compat,
3539 .check_args = function_check_args,
3540 .print = function_print,
3541 .print_type_decl = function_print_type_decl,
3542 .free_type = function_free_type,
3545 ###### declare terminals
3555 FuncName -> IDENTIFIER ${ {
3556 struct variable *v = var_decl(c, $1.txt);
3557 struct var *e = new_pos(var, $1);
3564 v = var_ref(c, $1.txt);
3566 type_err(c, "error: function '%v' redeclared",
3568 type_err(c, "info: this is where '%v' was first declared",
3569 v->where_decl, NULL, 0, NULL);
3575 Args -> ArgsLine NEWLINE ${ $0 = $<AL; }$
3576 | Args ArgsLine NEWLINE ${ {
3577 struct binode *b = $<AL;
3578 struct binode **bp = &b;
3580 bp = (struct binode **)&(*bp)->left;
3585 ArgsLine -> ${ $0 = NULL; }$
3586 | Varlist ${ $0 = $<1; }$
3587 | Varlist ; ${ $0 = $<1; }$
3589 Varlist -> Varlist ; ArgDecl ${
3590 $0 = new_pos(binode, $2);
3603 ArgDecl -> IDENTIFIER : FormalType ${ {
3604 struct variable *v = var_decl(c, $ID.txt);
3605 $0 = new_pos(var, $ID);
3612 ##### Function calls
3614 A function call can appear either as an expression or as a statement.
3615 We use a new 'Funcall' binode type to link the function with a list of
3616 arguments, form with the 'List' nodes.
3618 We have already seen the "Term" which is how a function call can appear
3619 in an expression. To parse a function call into a statement we include
3620 it in the "SimpleStatement Grammar" which will be described later.
3626 | Term ( ExpressionList ) ${ {
3627 struct binode *b = new(binode);
3630 b->right = reorder_bilist($<EL);
3634 struct binode *b = new(binode);
3641 ###### SimpleStatement Grammar
3643 | Term ( ExpressionList ) ${ {
3644 struct binode *b = new(binode);
3647 b->right = reorder_bilist($<EL);
3651 ###### print binode cases
3654 do_indent(indent, "");
3655 print_exec(b->left, -1, bracket);
3657 for (b = cast(binode, b->right); b; b = cast(binode, b->right)) {
3660 print_exec(b->left, -1, bracket);
3670 ###### propagate binode cases
3673 /* Every arg must match formal parameter, and result
3674 * is return type of function
3676 struct binode *args = cast(binode, b->right);
3677 struct var *v = cast(var, b->left);
3679 if (!v->var->type || v->var->type->check_args == NULL) {
3680 type_err(c, "error: attempt to call a non-function.",
3681 prog, NULL, 0, NULL);
3685 v->var->type->check_args(c, perr_local, v->var->type, args);
3686 if (v->var->type->function.inline_result)
3689 return v->var->type->function.return_type;
3692 ###### interp binode cases
3695 struct var *v = cast(var, b->left);
3696 struct type *t = v->var->type;
3697 void *oldlocal = c->local;
3698 int old_size = c->local_size;
3699 void *local = calloc(1, t->function.local_size);
3700 struct value *fbody = var_value(c, v->var);
3701 struct binode *arg = cast(binode, b->right);
3702 struct binode *param = t->function.params;
3705 struct var *pv = cast(var, param->left);
3706 struct type *vtype = NULL;
3707 struct value val = interp_exec(c, arg->left, &vtype);
3709 c->local = local; c->local_size = t->function.local_size;
3710 lval = var_value(c, pv->var);
3711 c->local = oldlocal; c->local_size = old_size;
3712 memcpy(lval, &val, vtype->size);
3713 param = cast(binode, param->right);
3714 arg = cast(binode, arg->right);
3716 c->local = local; c->local_size = t->function.local_size;
3717 if (t->function.inline_result && dtype) {
3718 _interp_exec(c, fbody->function, NULL, NULL);
3719 memcpy(dest, local, dtype->size);
3720 rvtype = ret.type = NULL;
3722 rv = interp_exec(c, fbody->function, &rvtype);
3723 c->local = oldlocal; c->local_size = old_size;
3728 ## Complex executables: statements and expressions
3730 Now that we have types and values and variables and most of the basic
3731 Terms which provide access to these, we can explore the more complex
3732 code that combine all of these to get useful work done. Specifically
3733 statements and expressions.
3735 Expressions are various combinations of Terms. We will use operator
3736 precedence to ensure correct parsing. The simplest Expression is just a
3737 Term - others will follow.
3742 Expression -> Term ${ $0 = $<Term; }$
3743 ## expression grammar
3745 ### Expressions: Conditional
3747 Our first user of the `binode` will be conditional expressions, which
3748 is a bit odd as they actually have three components. That will be
3749 handled by having 2 binodes for each expression. The conditional
3750 expression is the lowest precedence operator which is why we define it
3751 first - to start the precedence list.
3753 Conditional expressions are of the form "value `if` condition `else`
3754 other_value". They associate to the right, so everything to the right
3755 of `else` is part of an else value, while only a higher-precedence to
3756 the left of `if` is the if values. Between `if` and `else` there is no
3757 room for ambiguity, so a full conditional expression is allowed in
3763 ###### declare terminals
3767 ###### expression grammar
3769 | Expression if Expression else Expression $$ifelse ${ {
3770 struct binode *b1 = new(binode);
3771 struct binode *b2 = new(binode);
3781 ###### print binode cases
3784 b2 = cast(binode, b->right);
3785 if (bracket) printf("(");
3786 print_exec(b2->left, -1, bracket);
3788 print_exec(b->left, -1, bracket);
3790 print_exec(b2->right, -1, bracket);
3791 if (bracket) printf(")");
3794 ###### propagate binode cases
3797 /* cond must be Tbool, others must match */
3798 struct binode *b2 = cast(binode, b->right);
3801 propagate_types(b->left, c, perr_local, Tbool, 0);
3802 t = propagate_types(b2->left, c, perr, type, 0);
3803 t2 = propagate_types(b2->right, c, perr, type ?: t, 0);
3807 ###### interp binode cases
3810 struct binode *b2 = cast(binode, b->right);
3811 left = interp_exec(c, b->left, <ype);
3813 rv = interp_exec(c, b2->left, &rvtype); // UNTESTED
3815 rv = interp_exec(c, b2->right, &rvtype);
3821 We take a brief detour, now that we have expressions, to describe lists
3822 of expressions. These will be needed for function parameters and
3823 possibly other situations. They seem generic enough to introduce here
3824 to be used elsewhere.
3826 And ExpressionList will use the `List` type of `binode`, building up at
3827 the end. And place where they are used will probably call
3828 `reorder_bilist()` to get a more normal first/next arrangement.
3830 ###### declare terminals
3833 `List` execs have no implicit semantics, so they are never propagated or
3834 interpreted. The can be printed as a comma separate list, which is how
3835 they are parsed. Note they are also used for function formal parameter
3836 lists. In that case a separate function is used to print them.
3838 ###### print binode cases
3842 print_exec(b->left, -1, bracket);
3845 b = cast(binode, b->right);
3849 ###### propagate binode cases
3850 case List: abort(); // NOTEST
3851 ###### interp binode cases
3852 case List: abort(); // NOTEST
3857 ExpressionList -> ExpressionList , Expression ${
3870 ### Expressions: Boolean
3872 The next class of expressions to use the `binode` will be Boolean
3873 expressions. "`and then`" and "`or else`" are similar to `and` and `or`
3874 have same corresponding precendence. The difference is that they don't
3875 evaluate the second expression if not necessary.
3884 ###### declare terminals
3889 ###### expression grammar
3890 | Expression or Expression ${ {
3891 struct binode *b = new(binode);
3897 | Expression or else Expression ${ {
3898 struct binode *b = new(binode);
3905 | Expression and Expression ${ {
3906 struct binode *b = new(binode);
3912 | Expression and then Expression ${ {
3913 struct binode *b = new(binode);
3920 | not Expression ${ {
3921 struct binode *b = new(binode);
3927 ###### print binode cases
3929 if (bracket) printf("(");
3930 print_exec(b->left, -1, bracket);
3932 print_exec(b->right, -1, bracket);
3933 if (bracket) printf(")");
3936 if (bracket) printf("(");
3937 print_exec(b->left, -1, bracket);
3938 printf(" and then ");
3939 print_exec(b->right, -1, bracket);
3940 if (bracket) printf(")");
3943 if (bracket) printf("(");
3944 print_exec(b->left, -1, bracket);
3946 print_exec(b->right, -1, bracket);
3947 if (bracket) printf(")");
3950 if (bracket) printf("(");
3951 print_exec(b->left, -1, bracket);
3952 printf(" or else ");
3953 print_exec(b->right, -1, bracket);
3954 if (bracket) printf(")");
3957 if (bracket) printf("(");
3959 print_exec(b->right, -1, bracket);
3960 if (bracket) printf(")");
3963 ###### propagate binode cases
3969 /* both must be Tbool, result is Tbool */
3970 propagate_types(b->left, c, perr, Tbool, 0);
3971 propagate_types(b->right, c, perr, Tbool, 0);
3972 if (type && type != Tbool)
3973 type_err(c, "error: %1 operation found where %2 expected", prog,
3978 ###### interp binode cases
3980 rv = interp_exec(c, b->left, &rvtype);
3981 right = interp_exec(c, b->right, &rtype);
3982 rv.bool = rv.bool && right.bool;
3985 rv = interp_exec(c, b->left, &rvtype);
3987 rv = interp_exec(c, b->right, NULL);
3990 rv = interp_exec(c, b->left, &rvtype);
3991 right = interp_exec(c, b->right, &rtype);
3992 rv.bool = rv.bool || right.bool;
3995 rv = interp_exec(c, b->left, &rvtype);
3997 rv = interp_exec(c, b->right, NULL);
4000 rv = interp_exec(c, b->right, &rvtype);
4004 ### Expressions: Comparison
4006 Of slightly higher precedence that Boolean expressions are Comparisons.
4007 A comparison takes arguments of any comparable type, but the two types
4010 To simplify the parsing we introduce an `eop` which can record an
4011 expression operator, and the `CMPop` non-terminal will match one of them.
4018 ###### ast functions
4019 static void free_eop(struct eop *e)
4033 ###### declare terminals
4034 $LEFT < > <= >= == != CMPop
4036 ###### expression grammar
4037 | Expression CMPop Expression ${ {
4038 struct binode *b = new(binode);
4048 CMPop -> < ${ $0.op = Less; }$
4049 | > ${ $0.op = Gtr; }$
4050 | <= ${ $0.op = LessEq; }$
4051 | >= ${ $0.op = GtrEq; }$
4052 | == ${ $0.op = Eql; }$
4053 | != ${ $0.op = NEql; }$
4055 ###### print binode cases
4063 if (bracket) printf("(");
4064 print_exec(b->left, -1, bracket);
4066 case Less: printf(" < "); break;
4067 case LessEq: printf(" <= "); break;
4068 case Gtr: printf(" > "); break;
4069 case GtrEq: printf(" >= "); break;
4070 case Eql: printf(" == "); break;
4071 case NEql: printf(" != "); break;
4072 default: abort(); // NOTEST
4074 print_exec(b->right, -1, bracket);
4075 if (bracket) printf(")");
4078 ###### propagate binode cases
4085 /* Both must match but not be labels, result is Tbool */
4086 t = propagate_types(b->left, c, perr, NULL, 0);
4088 propagate_types(b->right, c, perr, t, 0);
4090 t = propagate_types(b->right, c, perr, NULL, 0); // UNTESTED
4092 t = propagate_types(b->left, c, perr, t, 0); // UNTESTED
4094 if (!type_compat(type, Tbool, 0))
4095 type_err(c, "error: Comparison returns %1 but %2 expected", prog,
4096 Tbool, rules, type);
4100 ###### interp binode cases
4109 left = interp_exec(c, b->left, <ype);
4110 right = interp_exec(c, b->right, &rtype);
4111 cmp = value_cmp(ltype, rtype, &left, &right);
4114 case Less: rv.bool = cmp < 0; break;
4115 case LessEq: rv.bool = cmp <= 0; break;
4116 case Gtr: rv.bool = cmp > 0; break;
4117 case GtrEq: rv.bool = cmp >= 0; break;
4118 case Eql: rv.bool = cmp == 0; break;
4119 case NEql: rv.bool = cmp != 0; break;
4120 default: rv.bool = 0; break; // NOTEST
4125 ### Expressions: Arithmetic etc.
4127 The remaining expressions with the highest precedence are arithmetic,
4128 string concatenation, string conversion, and testing. String concatenation
4129 (`++`) has the same precedence as multiplication and division, but lower
4132 Testing comes in two forms. A single question mark (`?`) is a uniary
4133 operator which converts come types into Boolean. The general meaning is
4134 "is this a value value" and there will be more uses as the language
4135 develops. A double questionmark (`??`) is a binary operator (Choose),
4136 with same precedence as multiplication, which returns the LHS if it
4137 tests successfully, else returns the RHS.
4139 String conversion is a temporary feature until I get a better type
4140 system. `$` is a prefix operator which expects a string and returns
4143 `+` and `-` are both infix and prefix operations (where they are
4144 absolute value and negation). These have different operator names.
4146 We also have a 'Bracket' operator which records where parentheses were
4147 found. This makes it easy to reproduce these when printing. Possibly I
4148 should only insert brackets were needed for precedence. Putting
4149 parentheses around an expression converts it into a Term,
4155 Absolute, Negate, Test,
4159 ###### declare terminals
4161 $LEFT * / % ++ ?? Top
4165 ###### expression grammar
4166 | Expression Eop Expression ${ {
4167 struct binode *b = new(binode);
4174 | Expression Top Expression ${ {
4175 struct binode *b = new(binode);
4182 | Uop Expression ${ {
4183 struct binode *b = new(binode);
4191 | ( Expression ) ${ {
4192 struct binode *b = new_pos(binode, $1);
4201 Eop -> + ${ $0.op = Plus; }$
4202 | - ${ $0.op = Minus; }$
4204 Uop -> + ${ $0.op = Absolute; }$
4205 | - ${ $0.op = Negate; }$
4206 | $ ${ $0.op = StringConv; }$
4207 | ? ${ $0.op = Test; }$
4209 Top -> * ${ $0.op = Times; }$
4210 | / ${ $0.op = Divide; }$
4211 | % ${ $0.op = Rem; }$
4212 | ++ ${ $0.op = Concat; }$
4213 | ?? ${ $0.op = Choose; }$
4215 ###### print binode cases
4223 if (bracket) printf("(");
4224 print_exec(b->left, indent, bracket);
4226 case Plus: fputs(" + ", stdout); break;
4227 case Minus: fputs(" - ", stdout); break;
4228 case Times: fputs(" * ", stdout); break;
4229 case Divide: fputs(" / ", stdout); break;
4230 case Rem: fputs(" % ", stdout); break;
4231 case Concat: fputs(" ++ ", stdout); break;
4232 case Choose: fputs(" ?? ", stdout); break;
4233 default: abort(); // NOTEST
4235 print_exec(b->right, indent, bracket);
4236 if (bracket) printf(")");
4242 if (bracket) printf("(");
4244 case Absolute: fputs("+", stdout); break;
4245 case Negate: fputs("-", stdout); break;
4246 case StringConv: fputs("$", stdout); break;
4247 case Test: fputs("?", stdout); break;
4248 default: abort(); // NOTEST
4250 print_exec(b->right, indent, bracket);
4251 if (bracket) printf(")");
4255 print_exec(b->right, indent, bracket);
4259 ###### propagate binode cases
4265 /* both must be numbers, result is Tnum */
4268 /* as propagate_types ignores a NULL,
4269 * unary ops fit here too */
4270 propagate_types(b->left, c, perr, Tnum, 0);
4271 propagate_types(b->right, c, perr, Tnum, 0);
4272 if (!type_compat(type, Tnum, 0))
4273 type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
4279 /* both must be Tstr, result is Tstr */
4280 propagate_types(b->left, c, perr, Tstr, 0);
4281 propagate_types(b->right, c, perr, Tstr, 0);
4282 if (!type_compat(type, Tstr, 0))
4283 type_err(c, "error: Concat returns %1 but %2 expected", prog,
4289 /* op must be string, result is number */
4290 propagate_types(b->left, c, perr, Tstr, 0);
4291 if (!type_compat(type, Tnum, 0))
4292 type_err(c, // UNTESTED
4293 "error: Can only convert string to number, not %1",
4294 prog, type, 0, NULL);
4299 /* LHS must support ->test, result is Tbool */
4300 t = propagate_types(b->right, c, perr, NULL, 0);
4302 type_err(c, "error: '?' requires a testable value, not %1",
4308 /* LHS and RHS must match and are returned. Must support
4311 t = propagate_types(b->left, c, perr, type, rules);
4312 t = propagate_types(b->right, c, perr, t, rules);
4313 if (t && t->test == NULL)
4314 type_err(c, "error: \"??\" requires a testable value, not %1",
4320 return propagate_types(b->right, c, perr, type, rules);
4322 ###### interp binode cases
4325 rv = interp_exec(c, b->left, &rvtype);
4326 right = interp_exec(c, b->right, &rtype);
4327 mpq_add(rv.num, rv.num, right.num);
4330 rv = interp_exec(c, b->left, &rvtype);
4331 right = interp_exec(c, b->right, &rtype);
4332 mpq_sub(rv.num, rv.num, right.num);
4335 rv = interp_exec(c, b->left, &rvtype);
4336 right = interp_exec(c, b->right, &rtype);
4337 mpq_mul(rv.num, rv.num, right.num);
4340 rv = interp_exec(c, b->left, &rvtype);
4341 right = interp_exec(c, b->right, &rtype);
4342 mpq_div(rv.num, rv.num, right.num);
4347 left = interp_exec(c, b->left, <ype);
4348 right = interp_exec(c, b->right, &rtype);
4349 mpz_init(l); mpz_init(r); mpz_init(rem);
4350 mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
4351 mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
4352 mpz_tdiv_r(rem, l, r);
4353 val_init(Tnum, &rv);
4354 mpq_set_z(rv.num, rem);
4355 mpz_clear(r); mpz_clear(l); mpz_clear(rem);
4360 rv = interp_exec(c, b->right, &rvtype);
4361 mpq_neg(rv.num, rv.num);
4364 rv = interp_exec(c, b->right, &rvtype);
4365 mpq_abs(rv.num, rv.num);
4368 rv = interp_exec(c, b->right, &rvtype);
4371 left = interp_exec(c, b->left, <ype);
4372 right = interp_exec(c, b->right, &rtype);
4374 rv.str = text_join(left.str, right.str);
4377 right = interp_exec(c, b->right, &rvtype);
4381 struct text tx = right.str;
4384 if (tx.txt[0] == '-') {
4385 neg = 1; // UNTESTED
4386 tx.txt++; // UNTESTED
4387 tx.len--; // UNTESTED
4389 if (number_parse(rv.num, tail, tx) == 0)
4390 mpq_init(rv.num); // UNTESTED
4392 mpq_neg(rv.num, rv.num); // UNTESTED
4394 printf("Unsupported suffix: %.*s\n", tx.len, tx.txt); // UNTESTED
4398 right = interp_exec(c, b->right, &rtype);
4400 rv.bool = !!rtype->test(rtype, &right);
4403 left = interp_exec(c, b->left, <ype);
4404 if (ltype->test(ltype, &left)) {
4409 rv = interp_exec(c, b->right, &rvtype);
4412 ###### value functions
4414 static struct text text_join(struct text a, struct text b)
4417 rv.len = a.len + b.len;
4418 rv.txt = malloc(rv.len);
4419 memcpy(rv.txt, a.txt, a.len);
4420 memcpy(rv.txt+a.len, b.txt, b.len);
4424 ### Blocks, Statements, and Statement lists.
4426 Now that we have expressions out of the way we need to turn to
4427 statements. There are simple statements and more complex statements.
4428 Simple statements do not contain (syntactic) newlines, complex statements do.
4430 Statements often come in sequences and we have corresponding simple
4431 statement lists and complex statement lists.
4432 The former comprise only simple statements separated by semicolons.
4433 The later comprise complex statements and simple statement lists. They are
4434 separated by newlines. Thus the semicolon is only used to separate
4435 simple statements on the one line. This may be overly restrictive,
4436 but I'm not sure I ever want a complex statement to share a line with
4439 Note that a simple statement list can still use multiple lines if
4440 subsequent lines are indented, so
4442 ###### Example: wrapped simple statement list
4447 is a single simple statement list. This might allow room for
4448 confusion, so I'm not set on it yet.
4450 A simple statement list needs no extra syntax. A complex statement
4451 list has two syntactic forms. It can be enclosed in braces (much like
4452 C blocks), or it can be introduced by an indent and continue until an
4453 unindented newline (much like Python blocks). With this extra syntax
4454 it is referred to as a block.
4456 Note that a block does not have to include any newlines if it only
4457 contains simple statements. So both of:
4459 if condition: a=b; d=f
4461 if condition { a=b; print f }
4465 In either case the list is constructed from a `binode` list with
4466 `Block` as the operator. When parsing the list it is most convenient
4467 to append to the end, so a list is a list and a statement. When using
4468 the list it is more convenient to consider a list to be a statement
4469 and a list. So we need a function to re-order a list.
4470 `reorder_bilist` serves this purpose.
4472 The only stand-alone statement we introduce at this stage is `pass`
4473 which does nothing and is represented as a `NULL` pointer in a `Block`
4474 list. Other stand-alone statements will follow once the infrastructure
4477 As many statements will use binodes, we declare a binode pointer 'b' in
4478 the common header for all reductions to use.
4480 ###### Parser: reduce
4491 Block -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4492 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4493 | SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
4494 | SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
4495 | IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
4497 OpenBlock -> OpenScope { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4498 | OpenScope { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4499 | OpenScope SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
4500 | OpenScope SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
4501 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
4503 UseBlock -> { OpenScope IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4504 | { OpenScope SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4505 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
4507 ColonBlock -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4508 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4509 | : SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
4510 | : SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
4511 | : IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
4513 Statementlist -> ComplexStatements ${ $0 = reorder_bilist($<CS); }$
4515 ComplexStatements -> ComplexStatements ComplexStatement ${
4525 | ComplexStatement ${
4537 ComplexStatement -> SimpleStatements Newlines ${
4538 $0 = reorder_bilist($<SS);
4540 | SimpleStatements ; Newlines ${
4541 $0 = reorder_bilist($<SS);
4543 ## ComplexStatement Grammar
4546 SimpleStatements -> SimpleStatements ; SimpleStatement ${
4552 | SimpleStatement ${
4561 SimpleStatement -> pass ${ $0 = NULL; }$
4562 | ERROR ${ tok_err(c, "Syntax error in statement", &$1); }$
4563 ## SimpleStatement Grammar
4565 ###### print binode cases
4569 if (b->left == NULL) // UNTESTED
4570 printf("pass"); // UNTESTED
4572 print_exec(b->left, indent, bracket); // UNTESTED
4573 if (b->right) { // UNTESTED
4574 printf("; "); // UNTESTED
4575 print_exec(b->right, indent, bracket); // UNTESTED
4578 // block, one per line
4579 if (b->left == NULL)
4580 do_indent(indent, "pass\n");
4582 print_exec(b->left, indent, bracket);
4584 print_exec(b->right, indent, bracket);
4588 ###### propagate binode cases
4591 /* If any statement returns something other than Tnone
4592 * or Tbool then all such must return same type.
4593 * As each statement may be Tnone or something else,
4594 * we must always pass NULL (unknown) down, otherwise an incorrect
4595 * error might occur. We never return Tnone unless it is
4600 for (e = b; e; e = cast(binode, e->right)) {
4601 t = propagate_types(e->left, c, perr, NULL, rules);
4602 if ((rules & Rboolok) && (t == Tbool || t == Tnone))
4604 if (t == Tnone && e->right)
4605 /* Only the final statement *must* return a value
4613 type_err(c, "error: expected %1, found %2",
4614 e->left, type, rules, t);
4620 ###### interp binode cases
4622 while (rvtype == Tnone &&
4625 rv = interp_exec(c, b->left, &rvtype);
4626 b = cast(binode, b->right);
4630 ### The Print statement
4632 `print` is a simple statement that takes a comma-separated list of
4633 expressions and prints the values separated by spaces and terminated
4634 by a newline. No control of formatting is possible.
4636 `print` uses `ExpressionList` to collect the expressions and stores them
4637 on the left side of a `Print` binode unlessthere is a trailing comma
4638 when the list is stored on the `right` side and no trailing newline is
4644 ##### declare terminals
4647 ###### SimpleStatement Grammar
4649 | print ExpressionList ${
4650 $0 = b = new_pos(binode, $1);
4653 b->left = reorder_bilist($<EL);
4655 | print ExpressionList , ${ {
4656 $0 = b = new_pos(binode, $1);
4658 b->right = reorder_bilist($<EL);
4662 $0 = b = new_pos(binode, $1);
4668 ###### print binode cases
4671 do_indent(indent, "print");
4673 print_exec(b->right, -1, bracket);
4676 print_exec(b->left, -1, bracket);
4681 ###### propagate binode cases
4684 /* don't care but all must be consistent */
4686 b = cast(binode, b->left);
4688 b = cast(binode, b->right);
4690 propagate_types(b->left, c, perr_local, NULL, 0);
4691 b = cast(binode, b->right);
4695 ###### interp binode cases
4699 struct binode *b2 = cast(binode, b->left);
4701 b2 = cast(binode, b->right);
4702 for (; b2; b2 = cast(binode, b2->right)) {
4703 left = interp_exec(c, b2->left, <ype);
4704 print_value(ltype, &left, stdout);
4705 free_value(ltype, &left);
4709 if (b->right == NULL)
4715 ###### Assignment statement
4717 An assignment will assign a value to a variable, providing it hasn't
4718 been declared as a constant. The analysis phase ensures that the type
4719 will be correct so the interpreter just needs to perform the
4720 calculation. There is a form of assignment which declares a new
4721 variable as well as assigning a value. If a name is used before
4722 it is declared, it is assumed to be a global constant which are allowed to
4723 be declared at any time.
4727 Declare, DeclareRef,
4729 ###### declare terminals
4732 ###### SimpleStatement Grammar
4733 | Term = Expression ${
4734 $0 = b= new(binode);
4739 | VariableDecl = Expression ${
4740 $0 = b= new(binode);
4747 if ($1->var->where_set == NULL) {
4749 "Variable declared with no type or value: %v",
4753 $0 = b = new(binode);
4760 ###### print binode cases
4764 do_indent(indent, "");
4765 print_exec(b->left, -1, bracket);
4767 print_exec(b->right, -1, bracket);
4775 struct variable *v = cast(var, b->left)->var;
4776 do_indent(indent, "");
4777 print_exec(b->left, -1, bracket);
4778 if (cast(var, b->left)->var->constant) {
4780 if (v->explicit_type) {
4781 type_print(v->type, stdout);
4786 if (v->explicit_type) {
4787 type_print(v->type, stdout);
4793 print_exec(b->right, -1, bracket);
4800 ###### propagate binode cases
4806 /* Both must match, or left may be ref and right an lval
4807 * Type must support 'dup',
4808 * For Assign, left must not be constant.
4811 *perr &= ~(Erval | Econst);
4812 t = propagate_types(b->left, c, perr, NULL, 0);
4817 struct type *t2 = propagate_types(b->right, c, perr_local,
4819 if (!t2 || t2 == t || (*perr_local & Efail))
4820 ; // No more effort needed
4821 else if (t->free == reference_free &&
4822 t->reference.referent == t2 &&
4823 !(*perr_local & Erval)) {
4824 if (b->op == Assign)
4826 if (b->op == Declare)
4829 else if (t->free == reference_free &&
4830 t->reference.referent == t2 &&
4831 (*perr_local & Erval))
4832 type_err(c, "error: Cannot assign an rval to a reference.",
4835 t = propagate_types(b->right, c, perr_local, NULL, 0);
4837 propagate_types(b->left, c, perr, t, 0);
4840 type_err(c, "error: cannot assign to an rval", b,
4842 else if ((b->op == Assign || b->op == AssignRef) && (*perr & Econst)) {
4843 type_err(c, "error: Cannot assign to a constant: %v",
4844 b->left, NULL, 0, NULL);
4845 if (b->left->type == Xvar) {
4846 struct var *var = cast(var, b->left);
4847 struct variable *v = var->var;
4848 type_err(c, "info: name was defined as a constant here",
4849 v->where_decl, NULL, 0, NULL);
4852 if (t && t->dup == NULL && !(*perr_local & Emaycopy))
4853 type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
4854 if (b->left->type == Xvar && (*perr_local & Efail))
4855 type_err(c, "info: variable '%v' was set as %1 here.",
4856 cast(var, b->left)->var->where_set, t, rules, NULL);
4861 ###### interp binode cases
4865 lleft = linterp_exec(c, b->left, <ype);
4867 // FIXME lleft==NULL probably means illegal array ref
4868 // should that cause a runtime error
4870 else if (b->op == AssignRef)
4871 lleft->ref = linterp_exec(c, b->right, &rtype);
4873 dinterp_exec(c, b->right, lleft, ltype, 1);
4880 struct variable *v = cast(var, b->left)->var;
4883 val = var_value(c, v);
4884 if (v->type->prepare_type)
4885 v->type->prepare_type(c, v->type, 0);
4887 val_init(v->type, val);
4888 else if (b->op == DeclareRef)
4889 val->ref = linterp_exec(c, b->right, &rtype);
4891 dinterp_exec(c, b->right, val, v->type, 0);
4895 ### The `use` statement
4897 The `use` statement is the last "simple" statement. It is needed when a
4898 statement block can return a value. This includes the body of a
4899 function which has a return type, and the "condition" code blocks in
4900 `if`, `while`, and `switch` statements.
4905 ###### declare terminals
4908 ###### SimpleStatement Grammar
4910 $0 = b = new_pos(binode, $1);
4915 ###### print binode cases
4918 do_indent(indent, "use ");
4919 print_exec(b->right, -1, bracket);
4924 ###### propagate binode cases
4927 /* result matches value */
4928 return propagate_types(b->right, c, perr, type, 0);
4930 ###### interp binode cases
4933 rv = interp_exec(c, b->right, &rvtype);
4936 ### The Conditional Statement
4938 This is the biggy and currently the only complex statement. This
4939 subsumes `if`, `while`, `do/while`, `switch`, and some parts of `for`.
4940 It is comprised of a number of parts, all of which are optional though
4941 set combinations apply. Each part is (usually) a key word (`then` is
4942 sometimes optional) followed by either an expression or a code block,
4943 except the `casepart` which is a "key word and an expression" followed
4944 by a code block. The code-block option is valid for all parts and,
4945 where an expression is also allowed, the code block can use the `use`
4946 statement to report a value. If the code block does not report a value
4947 the effect is similar to reporting `True`.
4949 The `else` and `case` parts, as well as `then` when combined with
4950 `if`, can contain a `use` statement which will apply to some
4951 containing conditional statement. `for` parts, `do` parts and `then`
4952 parts used with `for` can never contain a `use`, except in some
4953 subordinate conditional statement.
4955 If there is a `forpart`, it is executed first, only once.
4956 If there is a `dopart`, then it is executed repeatedly providing
4957 always that the `condpart` or `cond`, if present, does not return a non-True
4958 value. `condpart` can fail to return any value if it simply executes
4959 to completion. This is treated the same as returning `True`.
4961 If there is a `thenpart` it will be executed whenever the `condpart`
4962 or `cond` returns True (or does not return any value), but this will happen
4963 *after* `dopart` (when present).
4965 If `elsepart` is present it will be executed at most once when the
4966 condition returns `False` or some value that isn't `True` and isn't
4967 matched by any `casepart`. If there are any `casepart`s, they will be
4968 executed when the condition returns a matching value.
4970 The particular sorts of values allowed in case parts has not yet been
4971 determined in the language design, so nothing is prohibited.
4973 The various blocks in this complex statement potentially provide scope
4974 for variables as described earlier. Each such block must include the
4975 "OpenScope" nonterminal before parsing the block, and must call
4976 `var_block_close()` when closing the block.
4978 The code following "`if`", "`switch`" and "`for`" does not get its own
4979 scope, but is in a scope covering the whole statement, so names
4980 declared there cannot be redeclared elsewhere. Similarly the
4981 condition following "`while`" is in a scope the covers the body
4982 ("`do`" part) of the loop, and which does not allow conditional scope
4983 extension. Code following "`then`" (both looping and non-looping),
4984 "`else`" and "`case`" each get their own local scope.
4986 The type requirements on the code block in a `whilepart` are quite
4987 unusal. It is allowed to return a value of some identifiable type, in
4988 which case the loop aborts and an appropriate `casepart` is run, or it
4989 can return a Boolean, in which case the loop either continues to the
4990 `dopart` (on `True`) or aborts and runs the `elsepart` (on `False`).
4991 This is different both from the `ifpart` code block which is expected to
4992 return a Boolean, or the `switchpart` code block which is expected to
4993 return the same type as the casepart values. The correct analysis of
4994 the type of the `whilepart` code block is the reason for the
4995 `Rboolok` flag which is passed to `propagate_types()`.
4997 The `cond_statement` cannot fit into a `binode` so a new `exec` is
4998 defined. As there are two scopes which cover multiple parts - one for
4999 the whole statement and one for "while" and "do" - and as we will use
5000 the 'struct exec' to track scopes, we actually need two new types of
5001 exec. One is a `binode` for the looping part, the rest is the
5002 `cond_statement`. The `cond_statement` will use an auxilliary `struct
5003 casepart` to track a list of case parts.
5014 struct exec *action;
5015 struct casepart *next;
5017 struct cond_statement {
5019 struct exec *forpart, *condpart, *thenpart, *elsepart;
5020 struct binode *looppart;
5021 struct casepart *casepart;
5024 ###### ast functions
5026 static void free_casepart(struct casepart *cp)
5030 free_exec(cp->value);
5031 free_exec(cp->action);
5038 static void free_cond_statement(struct cond_statement *s)
5042 free_exec(s->forpart);
5043 free_exec(s->condpart);
5044 free_exec(s->looppart);
5045 free_exec(s->thenpart);
5046 free_exec(s->elsepart);
5047 free_casepart(s->casepart);
5051 ###### free exec cases
5052 case Xcond_statement: free_cond_statement(cast(cond_statement, e)); break;
5054 ###### ComplexStatement Grammar
5055 | CondStatement ${ $0 = $<1; }$
5057 ###### declare terminals
5058 $TERM for then while do
5065 // A CondStatement must end with EOL, as does CondSuffix and
5067 // ForPart, ThenPart, SwitchPart, CasePart are non-empty and
5068 // may or may not end with EOL
5069 // WhilePart and IfPart include an appropriate Suffix
5071 // ForPart, SwitchPart, and IfPart open scopes, o we have to close
5072 // them. WhilePart opens and closes its own scope.
5073 CondStatement -> ForPart OptNL ThenPart OptNL WhilePart CondSuffix ${
5076 $0->thenpart = $<TP;
5077 $0->looppart = $<WP;
5078 var_block_close(c, CloseSequential, $0);
5080 | ForPart OptNL WhilePart CondSuffix ${
5083 $0->looppart = $<WP;
5084 var_block_close(c, CloseSequential, $0);
5086 | WhilePart CondSuffix ${
5088 $0->looppart = $<WP;
5090 | SwitchPart OptNL CasePart CondSuffix ${
5092 $0->condpart = $<SP;
5093 $CP->next = $0->casepart;
5094 $0->casepart = $<CP;
5095 var_block_close(c, CloseSequential, $0);
5097 | SwitchPart : IN OptNL CasePart CondSuffix OUT Newlines ${
5099 $0->condpart = $<SP;
5100 $CP->next = $0->casepart;
5101 $0->casepart = $<CP;
5102 var_block_close(c, CloseSequential, $0);
5104 | IfPart IfSuffix ${
5106 $0->condpart = $IP.condpart; $IP.condpart = NULL;
5107 $0->thenpart = $IP.thenpart; $IP.thenpart = NULL;
5108 // This is where we close an "if" statement
5109 var_block_close(c, CloseSequential, $0);
5112 CondSuffix -> IfSuffix ${
5115 | Newlines CasePart CondSuffix ${
5117 $CP->next = $0->casepart;
5118 $0->casepart = $<CP;
5120 | CasePart CondSuffix ${
5122 $CP->next = $0->casepart;
5123 $0->casepart = $<CP;
5126 IfSuffix -> Newlines ${ $0 = new(cond_statement); }$
5127 | Newlines ElsePart ${ $0 = $<EP; }$
5128 | ElsePart ${$0 = $<EP; }$
5130 ElsePart -> else OpenBlock Newlines ${
5131 $0 = new(cond_statement);
5132 $0->elsepart = $<OB;
5133 var_block_close(c, CloseElse, $0->elsepart);
5135 | else OpenScope CondStatement ${
5136 $0 = new(cond_statement);
5137 $0->elsepart = $<CS;
5138 var_block_close(c, CloseElse, $0->elsepart);
5142 CasePart -> case Expression OpenScope ColonBlock ${
5143 $0 = calloc(1,sizeof(struct casepart));
5146 var_block_close(c, CloseParallel, $0->action);
5150 // These scopes are closed in CondStatement
5151 ForPart -> for OpenBlock ${
5155 ThenPart -> then OpenBlock ${
5157 var_block_close(c, CloseSequential, $0);
5161 // This scope is closed in CondStatement
5162 WhilePart -> while UseBlock OptNL do OpenBlock ${
5167 var_block_close(c, CloseSequential, $0->right);
5168 var_block_close(c, CloseSequential, $0);
5170 | while OpenScope Expression OpenScope ColonBlock ${
5175 var_block_close(c, CloseSequential, $0->right);
5176 var_block_close(c, CloseSequential, $0);
5180 IfPart -> if UseBlock OptNL then OpenBlock ${
5183 var_block_close(c, CloseParallel, $0.thenpart);
5185 | if OpenScope Expression OpenScope ColonBlock ${
5188 var_block_close(c, CloseParallel, $0.thenpart);
5190 | if OpenScope Expression OpenScope OptNL then Block ${
5193 var_block_close(c, CloseParallel, $0.thenpart);
5197 // This scope is closed in CondStatement
5198 SwitchPart -> switch OpenScope Expression ${
5201 | switch UseBlock ${
5205 ###### print binode cases
5207 if (b->left && b->left->type == Xbinode &&
5208 cast(binode, b->left)->op == Block) {
5210 do_indent(indent, "while {\n");
5212 do_indent(indent, "while\n");
5213 print_exec(b->left, indent+1, bracket);
5215 do_indent(indent, "} do {\n");
5217 do_indent(indent, "do\n");
5218 print_exec(b->right, indent+1, bracket);
5220 do_indent(indent, "}\n");
5222 do_indent(indent, "while ");
5223 print_exec(b->left, 0, bracket);
5228 print_exec(b->right, indent+1, bracket);
5230 do_indent(indent, "}\n");
5234 ###### print exec cases
5236 case Xcond_statement:
5238 struct cond_statement *cs = cast(cond_statement, e);
5239 struct casepart *cp;
5241 do_indent(indent, "for");
5242 if (bracket) printf(" {\n"); else printf("\n");
5243 print_exec(cs->forpart, indent+1, bracket);
5246 do_indent(indent, "} then {\n");
5248 do_indent(indent, "then\n");
5249 print_exec(cs->thenpart, indent+1, bracket);
5251 if (bracket) do_indent(indent, "}\n");
5254 print_exec(cs->looppart, indent, bracket);
5258 do_indent(indent, "switch");
5260 do_indent(indent, "if");
5261 if (cs->condpart && cs->condpart->type == Xbinode &&
5262 cast(binode, cs->condpart)->op == Block) {
5267 print_exec(cs->condpart, indent+1, bracket);
5269 do_indent(indent, "}\n");
5271 do_indent(indent, "then\n");
5272 print_exec(cs->thenpart, indent+1, bracket);
5276 print_exec(cs->condpart, 0, bracket);
5282 print_exec(cs->thenpart, indent+1, bracket);
5284 do_indent(indent, "}\n");
5289 for (cp = cs->casepart; cp; cp = cp->next) {
5290 do_indent(indent, "case ");
5291 print_exec(cp->value, -1, 0);
5296 print_exec(cp->action, indent+1, bracket);
5298 do_indent(indent, "}\n");
5301 do_indent(indent, "else");
5306 print_exec(cs->elsepart, indent+1, bracket);
5308 do_indent(indent, "}\n");
5313 ###### propagate binode cases
5315 t = propagate_types(b->right, c, perr_local, Tnone, 0);
5316 if (!type_compat(Tnone, t, 0))
5317 *perr |= Efail; // UNTESTED
5318 return propagate_types(b->left, c, perr, type, rules);
5320 ###### propagate exec cases
5321 case Xcond_statement:
5323 // forpart and looppart->right must return Tnone
5324 // thenpart must return Tnone if there is a loopart,
5325 // otherwise it is like elsepart.
5327 // be bool if there is no casepart
5328 // match casepart->values if there is a switchpart
5329 // either be bool or match casepart->value if there
5331 // elsepart and casepart->action must match the return type
5332 // expected of this statement.
5333 struct cond_statement *cs = cast(cond_statement, prog);
5334 struct casepart *cp;
5336 t = propagate_types(cs->forpart, c, perr, Tnone, 0);
5337 if (!type_compat(Tnone, t, 0))
5338 *perr |= Efail; // UNTESTED
5341 t = propagate_types(cs->thenpart, c, perr, Tnone, 0);
5342 if (!type_compat(Tnone, t, 0))
5343 *perr |= Efail; // UNTESTED
5345 if (cs->casepart == NULL) {
5346 propagate_types(cs->condpart, c, perr, Tbool, 0);
5347 propagate_types(cs->looppart, c, perr, Tbool, 0);
5349 /* Condpart must match case values, with bool permitted */
5351 for (cp = cs->casepart;
5352 cp && !t; cp = cp->next)
5353 t = propagate_types(cp->value, c, perr, NULL, 0);
5354 if (!t && cs->condpart)
5355 t = propagate_types(cs->condpart, c, perr, NULL, Rboolok); // UNTESTED
5356 if (!t && cs->looppart)
5357 t = propagate_types(cs->looppart, c, perr, NULL, Rboolok); // UNTESTED
5358 // Now we have a type (I hope) push it down
5360 for (cp = cs->casepart; cp; cp = cp->next)
5361 propagate_types(cp->value, c, perr, t, 0);
5362 propagate_types(cs->condpart, c, perr, t, Rboolok);
5363 propagate_types(cs->looppart, c, perr, t, Rboolok);
5366 // (if)then, else, and case parts must return expected type.
5367 if (!cs->looppart && !type)
5368 type = propagate_types(cs->thenpart, c, perr, NULL, rules);
5370 type = propagate_types(cs->elsepart, c, perr, NULL, rules);
5371 for (cp = cs->casepart;
5373 cp = cp->next) // UNTESTED
5374 type = propagate_types(cp->action, c, perr, NULL, rules); // UNTESTED
5377 propagate_types(cs->thenpart, c, perr, type, rules);
5378 propagate_types(cs->elsepart, c, perr, type, rules);
5379 for (cp = cs->casepart; cp ; cp = cp->next)
5380 propagate_types(cp->action, c, perr, type, rules);
5386 ###### interp binode cases
5388 // This just performs one iterration of the loop
5389 rv = interp_exec(c, b->left, &rvtype);
5390 if (rvtype == Tnone ||
5391 (rvtype == Tbool && rv.bool != 0))
5392 // rvtype is Tnone or Tbool, doesn't need to be freed
5393 interp_exec(c, b->right, NULL);
5396 ###### interp exec cases
5397 case Xcond_statement:
5399 struct value v, cnd;
5400 struct type *vtype, *cndtype;
5401 struct casepart *cp;
5402 struct cond_statement *cs = cast(cond_statement, e);
5405 interp_exec(c, cs->forpart, NULL);
5407 while ((cnd = interp_exec(c, cs->looppart, &cndtype)),
5408 cndtype == Tnone || (cndtype == Tbool && cnd.bool != 0))
5409 interp_exec(c, cs->thenpart, NULL);
5411 cnd = interp_exec(c, cs->condpart, &cndtype);
5412 if ((cndtype == Tnone ||
5413 (cndtype == Tbool && cnd.bool != 0))) {
5414 // cnd is Tnone or Tbool, doesn't need to be freed
5415 rv = interp_exec(c, cs->thenpart, &rvtype);
5416 // skip else (and cases)
5420 for (cp = cs->casepart; cp; cp = cp->next) {
5421 v = interp_exec(c, cp->value, &vtype);
5422 if (value_cmp(cndtype, vtype, &v, &cnd) == 0) {
5423 free_value(vtype, &v);
5424 free_value(cndtype, &cnd);
5425 rv = interp_exec(c, cp->action, &rvtype);
5428 free_value(vtype, &v);
5430 free_value(cndtype, &cnd);
5432 rv = interp_exec(c, cs->elsepart, &rvtype);
5439 ### Top level structure
5441 All the language elements so far can be used in various places. Now
5442 it is time to clarify what those places are.
5444 At the top level of a file there will be a number of declarations.
5445 Many of the things that can be declared haven't been described yet,
5446 such as functions, procedures, imports, and probably more.
5447 For now there are two sorts of things that can appear at the top
5448 level. They are predefined constants, `struct` types, and the `main`
5449 function. While the syntax will allow the `main` function to appear
5450 multiple times, that will trigger an error if it is actually attempted.
5452 The various declarations do not return anything. They store the
5453 various declarations in the parse context.
5455 ###### Parser: grammar
5458 Ocean -> OptNL DeclarationList
5460 ## declare terminals
5468 DeclarationList -> Declaration
5469 | DeclarationList Declaration
5471 Declaration -> ERROR Newlines ${
5472 tok_err(c, // UNTESTED
5473 "error: unhandled parse error", &$1);
5479 ## top level grammar
5483 ### The `const` section
5485 As well as being defined in with the code that uses them, constants can
5486 be declared at the top level. These have full-file scope, so they are
5487 always `InScope`, even before(!) they have been declared. The value of
5488 a top level constant can be given as an expression, and this is
5489 evaluated after parsing and before execution.
5491 A function call can be used to evaluate a constant, but it will not have
5492 access to any program state, once such statement becomes meaningful.
5493 e.g. arguments and filesystem will not be visible.
5495 Constants are defined in a section that starts with the reserved word
5496 `const` and then has a block with a list of assignment statements.
5497 For syntactic consistency, these must use the double-colon syntax to
5498 make it clear that they are constants. Type can also be given: if
5499 not, the type will be determined during analysis, as with other
5502 ###### parse context
5503 struct binode *constlist;
5505 ###### top level grammar
5509 DeclareConstant -> const { IN OptNL ConstList OUT OptNL } Newlines
5510 | const { SimpleConstList } Newlines
5511 | const IN OptNL ConstList OUT Newlines
5512 | const SimpleConstList Newlines
5514 ConstList -> ConstList SimpleConstLine
5517 SimpleConstList -> SimpleConstList ; Const
5521 SimpleConstLine -> SimpleConstList Newlines
5522 | ERROR Newlines ${ tok_err(c, "Syntax error in constant", &$1); }$
5525 CType -> Type ${ $0 = $<1; }$
5529 Const -> IDENTIFIER :: CType = Expression ${ {
5531 struct binode *bl, *bv;
5532 struct var *var = new_pos(var, $ID);
5534 v = var_decl(c, $ID.txt);
5536 v->where_decl = var;
5542 v = var_ref(c, $1.txt);
5543 if (v->type == Tnone) {
5544 v->where_decl = var;
5550 tok_err(c, "error: name already declared", &$1);
5551 type_err(c, "info: this is where '%v' was first declared",
5552 v->where_decl, NULL, 0, NULL);
5564 bl->left = c->constlist;
5569 ###### core functions
5570 static void resolve_consts(struct parse_context *c)
5574 enum { none, some, cannot } progress = none;
5576 c->constlist = reorder_bilist(c->constlist);
5579 for (b = cast(binode, c->constlist); b;
5580 b = cast(binode, b->right)) {
5582 struct binode *vb = cast(binode, b->left);
5583 struct var *v = cast(var, vb->left);
5584 if (v->var->frame_pos >= 0)
5588 propagate_types(vb->right, c, &perr,
5590 } while (perr & Eretry);
5592 c->parse_error += 1;
5593 else if (!(perr & Eruntime)) {
5595 struct value res = interp_exec(
5596 c, vb->right, &v->var->type);
5597 global_alloc(c, v->var->type, v->var, &res);
5599 if (progress == cannot)
5600 type_err(c, "error: const %v cannot be resolved.",
5610 progress = cannot; break;
5612 progress = none; break;
5617 ###### print const decls
5622 for (b = cast(binode, context.constlist); b;
5623 b = cast(binode, b->right)) {
5624 struct binode *vb = cast(binode, b->left);
5625 struct var *vr = cast(var, vb->left);
5626 struct variable *v = vr->var;
5632 printf(" %.*s :: ", v->name->name.len, v->name->name.txt);
5633 type_print(v->type, stdout);
5635 print_exec(vb->right, -1, 0);
5640 ###### free const decls
5641 free_binode(context.constlist);
5643 ### Function declarations
5645 The code in an Ocean program is all stored in function declarations.
5646 One of the functions must be named `main` and it must accept an array of
5647 strings as a parameter - the command line arguments.
5649 As this is the top level, several things are handled a bit differently.
5650 The function is not interpreted by `interp_exec` as that isn't passed
5651 the argument list which the program requires. Similarly type analysis
5652 is a bit more interesting at this level.
5654 ###### ast functions
5656 static struct type *handle_results(struct parse_context *c,
5657 struct binode *results)
5659 /* Create a 'struct' type from the results list, which
5660 * is a list for 'struct var'
5662 struct type *t = add_anon_type(c, &structure_prototype,
5667 for (b = results; b; b = cast(binode, b->right))
5669 t->structure.nfields = cnt;
5670 t->structure.fields = calloc(cnt, sizeof(struct field));
5672 for (b = results; b; b = cast(binode, b->right)) {
5673 struct var *v = cast(var, b->left);
5674 struct field *f = &t->structure.fields[cnt++];
5675 int a = v->var->type->align;
5676 f->name = v->var->name->name;
5677 f->type = v->var->type;
5679 f->offset = t->size;
5680 v->var->frame_pos = f->offset;
5681 t->size += ((f->type->size - 1) | (a-1)) + 1;
5684 variable_unlink_exec(v->var);
5686 free_binode(results);
5690 static struct variable *declare_function(struct parse_context *c,
5691 struct variable *name,
5692 struct binode *args,
5694 struct binode *results,
5698 struct value fn = {.function = code};
5700 var_block_close(c, CloseFunction, code);
5701 t = add_anon_type(c, &function_prototype,
5702 "func %.*s", name->name->name.len,
5703 name->name->name.txt);
5705 t->function.params = reorder_bilist(args);
5707 ret = handle_results(c, reorder_bilist(results));
5708 t->function.inline_result = 1;
5709 t->function.local_size = ret->size;
5711 t->function.return_type = ret;
5712 global_alloc(c, t, name, &fn);
5713 name->type->function.scope = c->out_scope;
5718 var_block_close(c, CloseFunction, NULL);
5720 c->out_scope = NULL;
5724 ###### declare terminals
5727 ###### top level grammar
5730 DeclareFunction -> func FuncName ( OpenScope ArgsLine ) Block Newlines ${
5731 $0 = declare_function(c, $<FN, $<Ar, Tnone, NULL, $<Bl);
5733 | func FuncName IN OpenScope Args OUT OptNL do Block Newlines ${
5734 $0 = declare_function(c, $<FN, $<Ar, Tnone, NULL, $<Bl);
5736 | func FuncName NEWLINE OpenScope OptNL do Block Newlines ${
5737 $0 = declare_function(c, $<FN, NULL, Tnone, NULL, $<Bl);
5739 | func FuncName ( OpenScope ArgsLine ) : Type Block Newlines ${
5740 $0 = declare_function(c, $<FN, $<Ar, $<Ty, NULL, $<Bl);
5742 | func FuncName ( OpenScope ArgsLine ) : ( ArgsLine ) Block Newlines ${
5743 $0 = declare_function(c, $<FN, $<AL, NULL, $<AL2, $<Bl);
5745 | func FuncName IN OpenScope Args OUT OptNL return Type Newlines do Block Newlines ${
5746 $0 = declare_function(c, $<FN, $<Ar, $<Ty, NULL, $<Bl);
5748 | func FuncName NEWLINE OpenScope return Type Newlines do Block Newlines ${
5749 $0 = declare_function(c, $<FN, NULL, $<Ty, NULL, $<Bl);
5751 | func FuncName IN OpenScope Args OUT OptNL return IN Args OUT OptNL do Block Newlines ${
5752 $0 = declare_function(c, $<FN, $<Ar, NULL, $<Ar2, $<Bl);
5754 | func FuncName NEWLINE OpenScope return IN Args OUT OptNL do Block Newlines ${
5755 $0 = declare_function(c, $<FN, NULL, NULL, $<Ar, $<Bl);
5758 ###### print func decls
5763 while (target != 0) {
5765 for (v = context.in_scope; v; v=v->in_scope)
5766 if (v->depth == 0 && v->type && v->type->check_args) {
5775 struct value *val = var_value(&context, v);
5776 printf("func %.*s", v->name->name.len, v->name->name.txt);
5777 v->type->print_type_decl(v->type, stdout);
5779 print_exec(val->function, 0, brackets);
5781 print_value(v->type, val, stdout);
5782 printf("/* frame size %d */\n", v->type->function.local_size);
5788 ###### core functions
5790 static int analyse_funcs(struct parse_context *c)
5794 for (v = c->in_scope; v; v = v->in_scope) {
5798 if (v->depth != 0 || !v->type || !v->type->check_args)
5800 ret = v->type->function.inline_result ?
5801 Tnone : v->type->function.return_type;
5802 val = var_value(c, v);
5805 propagate_types(val->function, c, &perr, ret, 0);
5806 } while (!(perr & Efail) && (perr & Eretry));
5807 if (!(perr & Efail))
5808 /* Make sure everything is still consistent */
5809 propagate_types(val->function, c, &perr, ret, 0);
5812 if (!v->type->function.inline_result &&
5813 !v->type->function.return_type->dup) {
5814 type_err(c, "error: function cannot return value of type %1",
5815 v->where_decl, v->type->function.return_type, 0, NULL);
5818 scope_finalize(c, v->type);
5823 static int analyse_main(struct type *type, struct parse_context *c)
5825 struct binode *bp = type->function.params;
5829 struct type *argv_type;
5831 argv_type = add_anon_type(c, &array_prototype, "argv");
5832 argv_type->array.member = Tstr;
5833 argv_type->array.unspec = 1;
5835 for (b = bp; b; b = cast(binode, b->right)) {
5839 propagate_types(b->left, c, &perr, argv_type, 0);
5841 default: /* invalid */ // NOTEST
5842 propagate_types(b->left, c, &perr, Tnone, 0); // NOTEST
5845 c->parse_error += 1;
5848 return !c->parse_error;
5851 static void interp_main(struct parse_context *c, int argc, char **argv)
5853 struct value *progp = NULL;
5854 struct text main_name = { "main", 4 };
5855 struct variable *mainv;
5861 mainv = var_ref(c, main_name);
5863 progp = var_value(c, mainv);
5864 if (!progp || !progp->function) {
5865 fprintf(stderr, "oceani: no main function found.\n");
5866 c->parse_error += 1;
5869 if (!analyse_main(mainv->type, c)) {
5870 fprintf(stderr, "oceani: main has wrong type.\n");
5871 c->parse_error += 1;
5874 al = mainv->type->function.params;
5876 c->local_size = mainv->type->function.local_size;
5877 c->local = calloc(1, c->local_size);
5879 struct var *v = cast(var, al->left);
5880 struct value *vl = var_value(c, v->var);
5890 mpq_set_ui(argcq, argc, 1);
5891 memcpy(var_value(c, t->array.vsize), &argcq, sizeof(argcq));
5892 t->prepare_type(c, t, 0);
5893 array_init(v->var->type, vl);
5894 for (i = 0; i < argc; i++) {
5895 struct value *vl2 = vl->array + i * v->var->type->array.member->size;
5897 arg.str.txt = argv[i];
5898 arg.str.len = strlen(argv[i]);
5899 free_value(Tstr, vl2);
5900 dup_value(Tstr, &arg, vl2);
5904 al = cast(binode, al->right);
5906 v = interp_exec(c, progp->function, &vtype);
5907 free_value(vtype, &v);
5912 ###### ast functions
5913 void free_variable(struct variable *v)
5917 ## And now to test it out.
5919 Having a language requires having a "hello world" program. I'll
5920 provide a little more than that: a program that prints "Hello world"
5921 finds the GCD of two numbers, prints the first few elements of
5922 Fibonacci, performs a binary search for a number, and a few other
5923 things which will likely grow as the languages grows.
5925 ###### File: oceani.mk
5928 @echo "===== DEMO ====="
5929 ./oceani --section "demo: hello" oceani.mdc 55 33
5935 four ::= 2 + 2 ; five ::= 10/2
5936 const pie ::= "I like Pie";
5937 cake ::= "The cake is"
5945 func main(argv:[argc::]string)
5946 print "Hello World, what lovely oceans you have!"
5947 print "Are there", five, "?"
5948 print pi, pie, "but", cake
5950 A := $argv[1]; B := $argv[2]
5952 /* When a variable is defined in both branches of an 'if',
5953 * and used afterwards, the variables are merged.
5959 print "Is", A, "bigger than", B,"? ", bigger
5960 /* If a variable is not used after the 'if', no
5961 * merge happens, so types can be different
5964 double:string = "yes"
5965 print A, "is more than twice", B, "?", double
5968 print "double", B, "is", double
5973 if a > 0 and then b > 0:
5979 print "GCD of", A, "and", B,"is", a
5981 print a, "is not positive, cannot calculate GCD"
5983 print b, "is not positive, cannot calculate GCD"
5988 print "Fibonacci:", f1,f2,
5989 then togo = togo - 1
5997 /* Binary search... */
6002 mid := (lo + hi) / 2
6015 print "Yay, I found", target
6017 print "Closest I found was", lo
6022 // "middle square" PRNG. Not particularly good, but one my
6023 // Dad taught me - the first one I ever heard of.
6024 for i:=1; then i = i + 1; while i < size:
6025 n := list[i-1] * list[i-1]
6026 list[i] = (n / 100) % 10 000
6028 print "Before sort:",
6029 for i:=0; then i = i + 1; while i < size:
6033 for i := 1; then i=i+1; while i < size:
6034 for j:=i-1; then j=j-1; while j >= 0:
6035 if list[j] > list[j+1]:
6039 print " After sort:",
6040 for i:=0; then i = i + 1; while i < size:
6044 if 1 == 2 then print "yes"; else print "no"
6048 bob.alive = (bob.name == "Hello")
6049 print "bob", "is" if bob.alive else "isn't", "alive"