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 (which have since been remove), and the
41 "if ... else" trinary operator which can select between two expressions
42 based on a third (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)
1161 switch (tl->vtype) {
1162 case Vlabel: cmp = left->label == right->label ? 0 : 1; break;
1163 case Vnum: cmp = mpq_cmp(left->num, right->num); break;
1164 case Vstr: cmp = text_cmp(left->str, right->str); break;
1165 case Vbool: cmp = left->bool - right->bool; break;
1166 case Vnone: cmp = 0; // NOTEST
1171 static void _print_value(struct type *type, struct value *v, FILE *f)
1173 switch (type->vtype) {
1174 case Vnone: // NOTEST
1175 fprintf(f, "*no-value*"); break; // NOTEST
1176 case Vlabel: // NOTEST
1177 fprintf(f, "*label-%d*", v->label); break; // NOTEST
1179 fprintf(f, "%.*s", v->str.len, v->str.txt); break;
1181 fprintf(f, "%s", v->bool ? "True":"False"); break;
1186 mpf_set_q(fl, v->num);
1187 gmp_fprintf(f, "%.10Fg", fl);
1194 static void _free_value(struct type *type, struct value *v);
1196 static int bool_test(struct type *type, struct value *v)
1201 static struct type base_prototype = {
1203 .print = _print_value,
1204 .cmp_order = _value_cmp,
1205 .cmp_eq = _value_cmp,
1207 .free = _free_value,
1210 static struct type *Tbool, *Tstr, *Tnum, *Tnone, *Tlabel;
1212 ###### ast functions
1213 static struct type *add_base_type(struct parse_context *c, char *n,
1214 enum vtype vt, int size)
1216 struct text txt = { n, strlen(n) };
1219 t = add_type(c, txt, &base_prototype);
1222 t->align = size > sizeof(void*) ? sizeof(void*) : size;
1223 if (t->size & (t->align - 1))
1224 t->size = (t->size | (t->align - 1)) + 1; // NOTEST
1228 ###### context initialization
1230 Tbool = add_base_type(&context, "Boolean", Vbool, sizeof(char));
1231 Tbool->test = bool_test;
1232 Tstr = add_base_type(&context, "string", Vstr, sizeof(struct text));
1233 Tnum = add_base_type(&context, "number", Vnum, sizeof(mpq_t));
1234 Tnone = add_base_type(&context, "none", Vnone, 0);
1235 Tlabel = add_base_type(&context, "label", Vlabel, sizeof(void*));
1239 We have already met values as separate objects. When manifest constants
1240 appear in the program text, that must result in an executable which has
1241 a constant value. So the `val` structure embeds a value in an
1254 ###### ast functions
1255 struct val *new_val(struct type *T, struct token tk)
1257 struct val *v = new_pos(val, tk);
1262 ###### declare terminals
1269 $0 = new_val(Tbool, $1);
1273 $0 = new_val(Tbool, $1);
1278 $0 = new_val(Tnum, $1);
1279 if (number_parse($0->val.num, tail, $1.txt) == 0) {
1280 mpq_init($0->val.num);
1281 tok_err(c, "error: unsupported number format", &$NUM);
1283 tok_err(c, "error: unsupported number suffix", &$1);
1287 $0 = new_val(Tstr, $1);
1288 string_parse(&$1, '\\', &$0->val.str, tail);
1290 tok_err(c, "error: unsupported string suffix",
1295 $0 = new_val(Tstr, $1);
1296 string_parse(&$1, '\\', &$0->val.str, tail);
1298 tok_err(c, "error: unsupported string suffix",
1302 ###### print exec cases
1305 struct val *v = cast(val, e);
1306 if (v->vtype == Tstr)
1308 // FIXME how to ensure numbers have same precision.
1309 print_value(v->vtype, &v->val, stdout);
1310 if (v->vtype == Tstr)
1315 ###### propagate exec cases
1318 struct val *val = cast(val, prog);
1319 if (!type_compat(type, val->vtype, rules))
1320 type_err(c, "error: expected %1 found %2",
1321 prog, type, rules, val->vtype);
1326 ###### interp exec cases
1328 rvtype = cast(val, e)->vtype;
1329 dup_value(rvtype, &cast(val, e)->val, &rv);
1332 ###### ast functions
1333 static void free_val(struct val *v)
1336 free_value(v->vtype, &v->val);
1340 ###### free exec cases
1341 case Xval: free_val(cast(val, e)); break;
1343 ###### ast functions
1344 // Move all nodes from 'b' to 'rv', reversing their order.
1345 // In 'b' 'left' is a list, and 'right' is the last node.
1346 // In 'rv', left' is the first node and 'right' is a list.
1347 static struct binode *reorder_bilist(struct binode *b)
1349 struct binode *rv = NULL;
1352 struct exec *t = b->right;
1356 b = cast(binode, b->left);
1366 Labels are a temporary concept until I implement enums. There are an
1367 anonymous enum which is declared by usage. Thet are only allowed in
1368 `use` statements and corresponding `case` entries. They appear as a
1369 period followed by an identifier. All identifiers that are "used" must
1372 For now, we have a global list of labels, and don't check that all "use"
1384 ###### free exec cases
1388 ###### print exec cases
1390 struct label *l = cast(label, e);
1391 printf(".%.*s", l->name.len, l->name.txt);
1397 struct labels *next;
1401 ###### parse context
1402 struct labels *labels;
1404 ###### ast functions
1405 static int label_lookup(struct parse_context *c, struct text name)
1407 struct labels *l, **lp = &c->labels;
1408 while (*lp && text_cmp((*lp)->name, name) < 0)
1410 if (*lp && text_cmp((*lp)->name, name) == 0)
1411 return (*lp)->value;
1412 l = calloc(1, sizeof(*l));
1415 if (c->next_label == 0)
1417 l->value = c->next_label;
1423 ###### free context storage
1424 while (context.labels) {
1425 struct labels *l = context.labels;
1426 context.labels = l->next;
1430 ###### declare terminals
1434 struct label *l = new_pos(label, $ID);
1438 ###### propagate exec cases
1440 struct label *l = cast(label, prog);
1441 l->value = label_lookup(c, l->name);
1442 if (!type_compat(type, Tlabel, rules))
1443 type_err(c, "error: expected %1 found %2",
1444 prog, type, rules, Tlabel);
1448 ###### interp exec cases
1450 struct label *l = cast(label, e);
1451 rv.label = l->value;
1459 Variables are scoped named values. We store the names in a linked list
1460 of "bindings" sorted in lexical order, and use sequential search and
1467 struct binding *next; // in lexical order
1471 This linked list is stored in the parse context so that "reduce"
1472 functions can find or add variables, and so the analysis phase can
1473 ensure that every variable gets a type.
1475 ###### parse context
1477 struct binding *varlist; // In lexical order
1479 ###### ast functions
1481 static struct binding *find_binding(struct parse_context *c, struct text s)
1483 struct binding **l = &c->varlist;
1488 (cmp = text_cmp((*l)->name, s)) < 0)
1492 n = calloc(1, sizeof(*n));
1499 Each name can be linked to multiple variables defined in different
1500 scopes. Each scope starts where the name is declared and continues
1501 until the end of the containing code block. Scopes of a given name
1502 cannot nest, so a declaration while a name is in-scope is an error.
1504 ###### binding fields
1505 struct variable *var;
1509 struct variable *previous;
1511 struct binding *name;
1512 struct exec *where_decl;// where name was declared
1513 struct exec *where_set; // where type was set
1517 When a scope closes, the values of the variables might need to be freed.
1518 This happens in the context of some `struct exec` and each `exec` will
1519 need to know which variables need to be freed when it completes.
1522 struct variable *to_free;
1524 ####### variable fields
1525 struct exec *cleanup_exec;
1526 struct variable *next_free;
1528 ####### interp exec cleanup
1531 for (v = e->to_free; v; v = v->next_free) {
1532 struct value *val = var_value(c, v);
1533 free_value(v->type, val);
1537 ###### ast functions
1538 static void variable_unlink_exec(struct variable *v)
1540 struct variable **vp;
1541 if (!v->cleanup_exec)
1543 for (vp = &v->cleanup_exec->to_free;
1544 *vp; vp = &(*vp)->next_free) {
1548 v->cleanup_exec = NULL;
1553 While the naming seems strange, we include local constants in the
1554 definition of variables. A name declared `var := value` can
1555 subsequently be changed, but a name declared `var ::= value` cannot -
1558 ###### variable fields
1561 Scopes in parallel branches can be partially merged. More
1562 specifically, if a given name is declared in both branches of an
1563 if/else then its scope is a candidate for merging. Similarly if
1564 every branch of an exhaustive switch (e.g. has an "else" clause)
1565 declares a given name, then the scopes from the branches are
1566 candidates for merging.
1568 Note that names declared inside a loop (which is only parallel to
1569 itself) are never visible after the loop. Similarly names defined in
1570 scopes which are not parallel, such as those started by `for` and
1571 `switch`, are never visible after the scope. Only variables defined in
1572 both `then` and `else` (including the implicit then after an `if`, and
1573 excluding `then` used with `for`) and in all `case`s and `else` of a
1574 `switch` or `while` can be visible beyond the `if`/`switch`/`while`.
1576 Labels, which are a bit like variables, follow different rules.
1577 Labels are not explicitly declared, but if an undeclared name appears
1578 in a context where a label is legal, that effectively declares the
1579 name as a label. The declaration remains in force (or in scope) at
1580 least to the end of the immediately containing block and conditionally
1581 in any larger containing block which does not declare the name in some
1582 other way. Importantly, the conditional scope extension happens even
1583 if the label is only used in one parallel branch of a conditional --
1584 when used in one branch it is treated as having been declared in all
1587 Merge candidates are tentatively visible beyond the end of the
1588 branching statement which creates them. If the name is used, the
1589 merge is affirmed and they become a single variable visible at the
1590 outer layer. If not - if it is redeclared first - the merge lapses.
1592 To track scopes we have an extra stack, implemented as a linked list,
1593 which roughly parallels the parse stack and which is used exclusively
1594 for scoping. When a new scope is opened, a new frame is pushed and
1595 the child-count of the parent frame is incremented. This child-count
1596 is used to distinguish between the first of a set of parallel scopes,
1597 in which declared variables must not be in scope, and subsequent
1598 branches, whether they may already be conditionally scoped.
1600 We need a total ordering of scopes so we can easily compare to variables
1601 to see if they are concurrently in scope. To achieve this we record a
1602 `scope_count` which is actually a count of both beginnings and endings
1603 of scopes. Then each variable has a record of the scope count where it
1604 enters scope, and where it leaves.
1606 To push a new frame *before* any code in the frame is parsed, we need a
1607 grammar reduction. This is most easily achieved with a grammar
1608 element which derives the empty string, and creates the new scope when
1609 it is recognised. This can be placed, for example, between a keyword
1610 like "if" and the code following it.
1614 struct scope *parent;
1618 ###### parse context
1621 struct scope *scope_stack;
1623 ###### variable fields
1624 int scope_start, scope_end;
1626 ###### ast functions
1627 static void scope_pop(struct parse_context *c)
1629 struct scope *s = c->scope_stack;
1631 c->scope_stack = s->parent;
1633 c->scope_depth -= 1;
1634 c->scope_count += 1;
1637 static void scope_push(struct parse_context *c)
1639 struct scope *s = calloc(1, sizeof(*s));
1641 c->scope_stack->child_count += 1;
1642 s->parent = c->scope_stack;
1644 c->scope_depth += 1;
1645 c->scope_count += 1;
1651 OpenScope -> ${ scope_push(c); }$
1653 Each variable records a scope depth and is in one of four states:
1655 - "in scope". This is the case between the declaration of the
1656 variable and the end of the containing block, and also between
1657 the usage with affirms a merge and the end of that block.
1659 The scope depth is not greater than the current parse context scope
1660 nest depth. When the block of that depth closes, the state will
1661 change. To achieve this, all "in scope" variables are linked
1662 together as a stack in nesting order.
1664 - "pending". The "in scope" block has closed, but other parallel
1665 scopes are still being processed. So far, every parallel block at
1666 the same level that has closed has declared the name.
1668 The scope depth is the depth of the last parallel block that
1669 enclosed the declaration, and that has closed.
1671 - "conditionally in scope". The "in scope" block and all parallel
1672 scopes have closed, and no further mention of the name has been seen.
1673 This state includes a secondary nest depth (`min_depth`) which records
1674 the outermost scope seen since the variable became conditionally in
1675 scope. If a use of the name is found, the variable becomes "in scope"
1676 and that secondary depth becomes the recorded scope depth. If the
1677 name is declared as a new variable, the old variable becomes "out of
1678 scope" and the recorded scope depth stays unchanged.
1680 - "out of scope". The variable is neither in scope nor conditionally
1681 in scope. It is permanently out of scope now and can be removed from
1682 the "in scope" stack. When a variable becomes out-of-scope it is
1683 moved to a separate list (`out_scope`) of variables which have fully
1684 known scope. This will be used at the end of each function to assign
1685 each variable a place in the stack frame.
1687 ###### variable fields
1688 int depth, min_depth;
1689 enum { OutScope, PendingScope, CondScope, InScope } scope;
1690 struct variable *in_scope;
1692 ###### parse context
1694 struct variable *in_scope;
1695 struct variable *out_scope;
1697 All variables with the same name are linked together using the
1698 'previous' link. Those variable that have been affirmatively merged all
1699 have a 'merged' pointer that points to one primary variable - the most
1700 recently declared instance. When merging variables, we need to also
1701 adjust the 'merged' pointer on any other variables that had previously
1702 been merged with the one that will no longer be primary.
1704 A variable that is no longer the most recent instance of a name may
1705 still have "pending" scope, if it might still be merged with most
1706 recent instance. These variables don't really belong in the
1707 "in_scope" list, but are not immediately removed when a new instance
1708 is found. Instead, they are detected and ignored when considering the
1709 list of in_scope names.
1711 The storage of the value of a variable will be described later. For now
1712 we just need to know that when a variable goes out of scope, it might
1713 need to be freed. For this we need to be able to find it, so assume that
1714 `var_value()` will provide that.
1716 ###### variable fields
1717 struct variable *merged;
1719 ###### ast functions
1721 static void variable_merge(struct variable *primary, struct variable *secondary)
1725 primary = primary->merged;
1727 for (v = primary->previous; v; v=v->previous)
1728 if (v == secondary || v == secondary->merged ||
1729 v->merged == secondary ||
1730 v->merged == secondary->merged) {
1731 v->scope = OutScope;
1732 v->merged = primary;
1733 if (v->scope_start < primary->scope_start)
1734 primary->scope_start = v->scope_start;
1735 if (v->scope_end > primary->scope_end)
1736 primary->scope_end = v->scope_end; // NOTEST
1737 variable_unlink_exec(v);
1741 ###### forward decls
1742 static struct value *var_value(struct parse_context *c, struct variable *v);
1744 ###### free global vars
1746 while (context.varlist) {
1747 struct binding *b = context.varlist;
1748 struct variable *v = b->var;
1749 context.varlist = b->next;
1752 struct variable *next = v->previous;
1754 if (v->global && v->frame_pos >= 0) {
1755 free_value(v->type, var_value(&context, v));
1756 if (v->depth == 0 && v->type->free == function_free)
1757 // This is a function constant
1758 free_exec(v->where_decl);
1765 #### Manipulating Bindings
1767 When a name is conditionally visible, a new declaration discards the old
1768 binding - the condition lapses. Similarly when we reach the end of a
1769 function (outermost non-global scope) any conditional scope must lapse.
1770 Conversely a usage of the name affirms the visibility and extends it to
1771 the end of the containing block - i.e. the block that contains both the
1772 original declaration and the latest usage. This is determined from
1773 `min_depth`. When a conditionally visible variable gets affirmed like
1774 this, it is also merged with other conditionally visible variables with
1777 When we parse a variable declaration we either report an error if the
1778 name is currently bound, or create a new variable at the current nest
1779 depth if the name is unbound or bound to a conditionally scoped or
1780 pending-scope variable. If the previous variable was conditionally
1781 scoped, it and its homonyms becomes out-of-scope.
1783 When we parse a variable reference (including non-declarative assignment
1784 "foo = bar") we report an error if the name is not bound or is bound to
1785 a pending-scope variable; update the scope if the name is bound to a
1786 conditionally scoped variable; or just proceed normally if the named
1787 variable is in scope.
1789 When we exit a scope, any variables bound at this level are either
1790 marked out of scope or pending-scoped, depending on whether the scope
1791 was sequential or parallel. Here a "parallel" scope means the "then"
1792 or "else" part of a conditional, or any "case" or "else" branch of a
1793 switch. Other scopes are "sequential".
1795 When exiting a parallel scope we check if there are any variables that
1796 were previously pending and are still visible. If there are, then
1797 they weren't redeclared in the most recent scope, so they cannot be
1798 merged and must become out-of-scope. If it is not the first of
1799 parallel scopes (based on `child_count`), we check that there was a
1800 previous binding that is still pending-scope. If there isn't, the new
1801 variable must now be out-of-scope.
1803 When exiting a sequential scope that immediately enclosed parallel
1804 scopes, we need to resolve any pending-scope variables. If there was
1805 no `else` clause, and we cannot determine that the `switch` was exhaustive,
1806 we need to mark all pending-scope variable as out-of-scope. Otherwise
1807 all pending-scope variables become conditionally scoped.
1810 enum closetype { CloseSequential, CloseFunction, CloseParallel, CloseElse };
1812 ###### ast functions
1814 static struct variable *var_decl(struct parse_context *c, struct text s)
1816 struct binding *b = find_binding(c, s);
1817 struct variable *v = b->var;
1819 switch (v ? v->scope : OutScope) {
1821 /* Caller will report the error */
1825 v && v->scope == CondScope;
1827 v->scope = OutScope;
1831 v = calloc(1, sizeof(*v));
1832 v->previous = b->var;
1836 v->min_depth = v->depth = c->scope_depth;
1838 v->in_scope = c->in_scope;
1839 v->scope_start = c->scope_count;
1845 static struct variable *var_ref(struct parse_context *c, struct text s)
1847 struct binding *b = find_binding(c, s);
1848 struct variable *v = b->var;
1849 struct variable *v2;
1851 switch (v ? v->scope : OutScope) {
1854 /* Caller will report the error */
1857 /* All CondScope variables of this name need to be merged
1858 * and become InScope
1860 v->depth = v->min_depth;
1862 for (v2 = v->previous;
1863 v2 && v2->scope == CondScope;
1865 variable_merge(v, v2);
1873 static int var_refile(struct parse_context *c, struct variable *v)
1875 /* Variable just went out of scope. Add it to the out_scope
1876 * list, sorted by ->scope_start
1878 struct variable **vp = &c->out_scope;
1879 while ((*vp) && (*vp)->scope_start < v->scope_start)
1880 vp = &(*vp)->in_scope;
1886 static void var_block_close(struct parse_context *c, enum closetype ct,
1889 /* Close off all variables that are in_scope.
1890 * Some variables in c->scope may already be not-in-scope,
1891 * such as when a PendingScope variable is hidden by a new
1892 * variable with the same name.
1893 * So we check for v->name->var != v and drop them.
1894 * If we choose to make a variable OutScope, we drop it
1897 struct variable *v, **vp, *v2;
1900 for (vp = &c->in_scope;
1901 (v = *vp) && v->min_depth > c->scope_depth;
1902 (v->scope == OutScope || v->name->var != v)
1903 ? (*vp = v->in_scope, var_refile(c, v))
1904 : ( vp = &v->in_scope, 0)) {
1905 v->min_depth = c->scope_depth;
1906 if (v->name->var != v)
1907 /* This is still in scope, but we haven't just
1911 v->min_depth = c->scope_depth;
1912 if (v->scope == InScope)
1913 v->scope_end = c->scope_count;
1914 if (v->scope == InScope && e && !v->global) {
1915 /* This variable gets cleaned up when 'e' finishes */
1916 variable_unlink_exec(v);
1917 v->cleanup_exec = e;
1918 v->next_free = e->to_free;
1923 case CloseParallel: /* handle PendingScope */
1927 if (c->scope_stack->child_count == 1)
1928 /* first among parallel branches */
1929 v->scope = PendingScope;
1930 else if (v->previous &&
1931 v->previous->scope == PendingScope)
1932 /* all previous branches used name */
1933 v->scope = PendingScope;
1935 v->scope = OutScope;
1936 if (ct == CloseElse) {
1937 /* All Pending variables with this name
1938 * are now Conditional */
1940 v2 && v2->scope == PendingScope;
1942 v2->scope = CondScope;
1946 /* Not possible as it would require
1947 * parallel scope to be nested immediately
1948 * in a parallel scope, and that never
1952 /* Not possible as we already tested for
1959 if (v->scope == CondScope)
1960 /* Condition cannot continue past end of function */
1963 case CloseSequential:
1966 v->scope = OutScope;
1969 /* There was no 'else', so we can only become
1970 * conditional if we know the cases were exhaustive,
1971 * and that doesn't mean anything yet.
1972 * So only labels become conditional..
1975 v2 && v2->scope == PendingScope;
1977 v2->scope = OutScope;
1980 case OutScope: break;
1989 The value of a variable is store separately from the variable, on an
1990 analogue of a stack frame. There are (currently) two frames that can be
1991 active. A global frame which currently only stores constants, and a
1992 stacked frame which stores local variables. Each variable knows if it
1993 is global or not, and what its index into the frame is.
1995 Values in the global frame are known immediately they are relevant, so
1996 the frame needs to be reallocated as it grows so it can store those
1997 values. The local frame doesn't get values until the interpreted phase
1998 is started, so there is no need to allocate until the size is known.
2000 We initialize the `frame_pos` to an impossible value, so that we can
2001 tell if it was set or not later.
2003 ###### variable fields
2007 ###### variable init
2010 ###### parse context
2012 short global_size, global_alloc;
2014 void *global, *local;
2016 ###### forward decls
2017 static struct value *global_alloc(struct parse_context *c, struct type *t,
2018 struct variable *v, struct value *init);
2020 ###### ast functions
2022 static struct value *var_value(struct parse_context *c, struct variable *v)
2025 if (!c->local || !v->type)
2026 return NULL; // NOTEST
2027 if (v->frame_pos + v->type->size > c->local_size) {
2028 printf("INVALID frame_pos\n"); // NOTEST
2031 return c->local + v->frame_pos;
2033 if (c->global_size > c->global_alloc) {
2034 int old = c->global_alloc;
2035 c->global_alloc = (c->global_size | 1023) + 1024;
2036 c->global = realloc(c->global, c->global_alloc);
2037 memset(c->global + old, 0, c->global_alloc - old);
2039 return c->global + v->frame_pos;
2042 static struct value *global_alloc(struct parse_context *c, struct type *t,
2043 struct variable *v, struct value *init)
2046 struct variable scratch;
2048 if (t->prepare_type)
2049 t->prepare_type(c, t, 1); // NOTEST
2051 if (c->global_size & (t->align - 1))
2052 c->global_size = (c->global_size + t->align) & ~(t->align-1);
2057 v->frame_pos = c->global_size;
2059 c->global_size += v->type->size;
2060 ret = var_value(c, v);
2062 memcpy(ret, init, t->size);
2064 val_init(t, ret); // NOTEST
2068 As global values are found -- struct field initializers, labels etc --
2069 `global_alloc()` is called to record the value in the global frame.
2071 When the program is fully parsed, each function is analysed, we need to
2072 walk the list of variables local to that function and assign them an
2073 offset in the stack frame. For this we have `scope_finalize()`.
2075 We keep the stack from dense by re-using space for between variables
2076 that are not in scope at the same time. The `out_scope` list is sorted
2077 by `scope_start` and as we process a varible, we move it to an FIFO
2078 stack. For each variable we consider, we first discard any from the
2079 stack anything that went out of scope before the new variable came in.
2080 Then we place the new variable just after the one at the top of the
2083 ###### ast functions
2085 static void scope_finalize(struct parse_context *c, struct type *ft)
2087 int size = ft->function.local_size;
2088 struct variable *next = ft->function.scope;
2089 struct variable *done = NULL;
2092 struct variable *v = next;
2093 struct type *t = v->type;
2100 if (v->frame_pos >= 0)
2102 while (done && done->scope_end < v->scope_start)
2103 done = done->in_scope;
2105 pos = done->frame_pos + done->type->size;
2107 pos = ft->function.local_size;
2108 if (pos & (t->align - 1))
2109 pos = (pos + t->align) & ~(t->align-1);
2111 if (size < pos + v->type->size)
2112 size = pos + v->type->size;
2116 c->out_scope = NULL;
2117 ft->function.local_size = size;
2120 ###### free context storage
2121 free(context.global);
2123 #### Variables as executables
2125 Just as we used a `val` to wrap a value into an `exec`, we similarly
2126 need a `var` to wrap a `variable` into an exec. While each `val`
2127 contained a copy of the value, each `var` holds a link to the variable
2128 because it really is the same variable no matter where it appears.
2129 When a variable is used, we need to remember to follow the `->merged`
2130 link to find the primary instance.
2132 When a variable is declared, it may or may not be given an explicit
2133 type. We need to record which so that we can report the parsed code
2142 struct variable *var;
2145 ###### variable fields
2153 VariableDecl -> IDENTIFIER : ${ {
2154 struct variable *v = var_decl(c, $1.txt);
2155 $0 = new_pos(var, $1);
2160 v = var_ref(c, $1.txt);
2162 type_err(c, "error: variable '%v' redeclared",
2164 type_err(c, "info: this is where '%v' was first declared",
2165 v->where_decl, NULL, 0, NULL);
2168 | IDENTIFIER :: ${ {
2169 struct variable *v = var_decl(c, $1.txt);
2170 $0 = new_pos(var, $1);
2176 v = var_ref(c, $1.txt);
2178 type_err(c, "error: variable '%v' redeclared",
2180 type_err(c, "info: this is where '%v' was first declared",
2181 v->where_decl, NULL, 0, NULL);
2184 | IDENTIFIER : Type ${ {
2185 struct variable *v = var_decl(c, $1.txt);
2186 $0 = new_pos(var, $1);
2192 v->explicit_type = 1;
2194 v = var_ref(c, $1.txt);
2196 type_err(c, "error: variable '%v' redeclared",
2198 type_err(c, "info: this is where '%v' was first declared",
2199 v->where_decl, NULL, 0, NULL);
2202 | IDENTIFIER :: Type ${ {
2203 struct variable *v = var_decl(c, $1.txt);
2204 $0 = new_pos(var, $1);
2211 v->explicit_type = 1;
2213 v = var_ref(c, $1.txt);
2215 type_err(c, "error: variable '%v' redeclared",
2217 type_err(c, "info: this is where '%v' was first declared",
2218 v->where_decl, NULL, 0, NULL);
2223 Variable -> IDENTIFIER ${ {
2224 struct variable *v = var_ref(c, $1.txt);
2225 $0 = new_pos(var, $1);
2227 /* This might be a global const or a label
2228 * Allocate a var with impossible type Tnone,
2229 * which will be adjusted when we find out what it is,
2230 * or will trigger an error.
2232 v = var_decl(c, $1.txt);
2239 cast(var, $0)->var = v;
2242 ###### print exec cases
2245 struct var *v = cast(var, e);
2247 struct binding *b = v->var->name;
2248 printf("%.*s", b->name.len, b->name.txt);
2255 if (loc && loc->type == Xvar) {
2256 struct var *v = cast(var, loc);
2258 struct binding *b = v->var->name;
2259 fprintf(stderr, "%.*s", b->name.len, b->name.txt);
2261 fputs("???", stderr); // NOTEST
2263 fputs("NOTVAR", stderr); // NOTEST
2266 ###### propagate exec cases
2270 struct var *var = cast(var, prog);
2271 struct variable *v = var->var;
2273 type_err(c, "%d:BUG: no variable!!", prog, NULL, 0, NULL); // NOTEST
2274 return Tnone; // NOTEST
2277 if (v->type == Tnone && v->where_decl == prog)
2278 type_err(c, "error: variable used but not declared: %v",
2279 prog, NULL, 0, NULL);
2280 if (v->type == NULL) {
2281 if (type && !(*perr & Efail)) {
2283 v->where_set = prog;
2286 } else if (!type_compat(type, v->type, rules)) {
2287 type_err(c, "error: expected %1 but variable '%v' is %2", prog,
2288 type, rules, v->type);
2289 type_err(c, "info: this is where '%v' was set to %1", v->where_set,
2290 v->type, rules, NULL);
2292 if (!v->global || v->frame_pos < 0)
2299 ###### interp exec cases
2302 struct var *var = cast(var, e);
2303 struct variable *v = var->var;
2306 lrv = var_value(c, v);
2311 ###### ast functions
2313 static void free_var(struct var *v)
2318 ###### free exec cases
2319 case Xvar: free_var(cast(var, e)); break;
2324 Now that we have the shape of the interpreter in place we can add some
2325 complex types and connected them in to the data structures and the
2326 different phases of parse, analyse, print, interpret.
2328 Being "complex" the language will naturally have syntax to access
2329 specifics of objects of these types. These will fit into the grammar as
2330 "Terms" which are the things that are combined with various operators to
2331 form "Expression". Where a Term is formed by some operation on another
2332 Term, the subordinate Term will always come first, so for example a
2333 member of an array will be expressed as the Term for the array followed
2334 by an index in square brackets. The strict rule of using postfix
2335 operations makes precedence irrelevant within terms. To provide a place
2336 to put the grammar for each terms of each type, we will start out by
2337 introducing the "Term" grammar production, with contains at least a
2338 simple "Value" (to be explained later).
2342 Term -> Value ${ $0 = $<1; }$
2343 | Variable ${ $0 = $<1; }$
2346 Thus far the complex types we have are arrays and structs.
2350 Arrays can be declared by giving a size and a type, as `[size]type' so
2351 `freq:[26]number` declares `freq` to be an array of 26 numbers. The
2352 size can be either a literal number, or a named constant. Some day an
2353 arbitrary expression will be supported.
2355 As a formal parameter to a function, the array can be declared with a
2356 new variable as the size: `name:[size::number]string`. The `size`
2357 variable is set to the size of the array and must be a constant. As
2358 `number` is the only supported type, it can be left out:
2359 `name:[size::]string`.
2361 Arrays cannot be assigned. When pointers are introduced we will also
2362 introduce array slices which can refer to part or all of an array -
2363 the assignment syntax will create a slice. For now, an array can only
2364 ever be referenced by the name it is declared with. It is likely that
2365 a "`copy`" primitive will eventually be define which can be used to
2366 make a copy of an array with controllable recursive depth.
2368 For now we have two sorts of array, those with fixed size either because
2369 it is given as a literal number or because it is a struct member (which
2370 cannot have a runtime-changing size), and those with a size that is
2371 determined at runtime - local variables with a const size. The former
2372 have their size calculated at parse time, the latter at run time.
2374 For the latter type, the `size` field of the type is the size of a
2375 pointer, and the array is reallocated every time it comes into scope.
2377 We differentiate struct fields with a const size from local variables
2378 with a const size by whether they are prepared at parse time or not.
2380 ###### type union fields
2383 int unspec; // size is unspecified - vsize must be set.
2386 struct variable *vsize;
2387 struct type *member;
2390 ###### value union fields
2391 void *array; // used if not static_size
2393 ###### value functions
2395 static int array_prepare_type(struct parse_context *c, struct type *type,
2398 struct value *vsize;
2400 if (type->array.static_size)
2401 return 1; // NOTEST - guard against reentry
2402 if (type->array.unspec && parse_time)
2403 return 1; // NOTEST - unspec is still incomplete
2404 if (parse_time && type->array.vsize && !type->array.vsize->global)
2405 return 1; // NOTEST - should be impossible
2407 if (type->array.vsize) {
2408 vsize = var_value(c, type->array.vsize);
2410 return 1; // NOTEST - should be impossible
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; // NOTEST - error caught before here
2421 type->array.static_size = 1;
2422 type->size = type->array.size * type->array.member->size;
2423 type->align = type->array.member->align;
2428 static void array_init(struct type *type, struct value *val)
2431 void *ptr = val->ptr;
2435 if (!type->array.static_size) {
2436 val->array = calloc(type->array.size,
2437 type->array.member->size);
2440 for (i = 0; i < type->array.size; i++) {
2442 v = (void*)ptr + i * type->array.member->size;
2443 val_init(type->array.member, v);
2447 static void array_free(struct type *type, struct value *val)
2450 void *ptr = val->ptr;
2452 if (!type->array.static_size)
2454 for (i = 0; i < type->array.size; i++) {
2456 v = (void*)ptr + i * type->array.member->size;
2457 free_value(type->array.member, v);
2459 if (!type->array.static_size)
2463 static int array_compat(struct type *require, struct type *have,
2464 enum val_rules rules)
2466 if (have->compat != require->compat)
2468 /* Both are arrays, so we can look at details */
2469 if (!type_compat(require->array.member, have->array.member, 0))
2471 if (have->array.unspec && require->array.unspec &&
2472 have->array.size != require->array.size)
2474 if (have->array.unspec || require->array.unspec)
2476 if (require->array.vsize == NULL && have->array.vsize == NULL)
2477 return require->array.size == have->array.size;
2479 return require->array.vsize == have->array.vsize;
2482 static void array_print_type(struct type *type, FILE *f)
2485 if (type->array.vsize) {
2486 struct binding *b = type->array.vsize->name;
2487 fprintf(f, "%.*s%s]", b->name.len, b->name.txt,
2488 type->array.unspec ? "::" : "");
2489 } else if (type->array.size)
2490 fprintf(f, "%d]", type->array.size);
2493 type_print(type->array.member, f);
2496 static struct type array_prototype = {
2498 .prepare_type = array_prepare_type,
2499 .print_type = array_print_type,
2500 .compat = array_compat,
2502 .size = sizeof(void*),
2503 .align = sizeof(void*),
2506 ###### declare terminals
2511 | [ NUMBER ] Type ${ {
2517 if (number_parse(num, tail, $2.txt) == 0)
2518 tok_err(c, "error: unrecognised number", &$2);
2520 tok_err(c, "error: unsupported number suffix", &$2);
2523 elements = mpz_get_ui(mpq_numref(num));
2524 if (mpz_cmp_ui(mpq_denref(num), 1) != 0) {
2525 tok_err(c, "error: array size must be an integer",
2527 } else if (mpz_cmp_ui(mpq_numref(num), 1UL << 30) >= 0)
2528 tok_err(c, "error: array size is too large",
2533 $0 = t = add_anon_type(c, &array_prototype, "array[%d]", elements );
2534 t->array.size = elements;
2535 t->array.member = $<4;
2536 t->array.vsize = NULL;
2539 | [ IDENTIFIER ] Type ${ {
2540 struct variable *v = var_ref(c, $2.txt);
2543 tok_err(c, "error: name undeclared", &$2);
2544 else if (!v->constant)
2545 tok_err(c, "error: array size must be a constant", &$2);
2547 $0 = add_anon_type(c, &array_prototype, "array[%.*s]", $2.txt.len, $2.txt.txt);
2548 $0->array.member = $<4;
2550 $0->array.vsize = v;
2553 ###### formal type grammar
2556 $0 = add_anon_type(c, &array_prototype, "array[]");
2557 $0->array.member = $<Type;
2559 $0->array.unspec = 1;
2560 $0->array.vsize = NULL;
2568 | Term [ Expression ] ${ {
2569 struct binode *b = new(binode);
2577 struct binode *b = new(binode);
2583 ###### print binode cases
2585 print_exec(b->left, -1, bracket);
2587 print_exec(b->right, -1, bracket);
2592 print_exec(b->left, -1, bracket);
2596 ###### propagate binode cases
2598 /* left must be an array, right must be a number,
2599 * result is the member type of the array
2601 propagate_types(b->right, c, perr_local, Tnum, 0);
2602 t = propagate_types(b->left, c, perr, NULL, 0);
2603 if (!t || t->compat != array_compat) {
2604 type_err(c, "error: %1 cannot be indexed", prog, t, 0, NULL);
2607 if (!type_compat(type, t->array.member, rules)) {
2608 type_err(c, "error: have %1 but need %2", prog,
2609 t->array.member, rules, type);
2611 return t->array.member;
2616 /* left must be an array, result is a number
2618 t = propagate_types(b->left, c, perr, NULL, 0);
2619 if (!t || t->compat != array_compat) {
2620 type_err(c, "error: %1 cannot provide length", prog, t, 0, NULL);
2623 if (!type_compat(type, Tnum, rules))
2624 type_err(c, "error: have %1 but need %2", prog,
2629 ###### interp binode cases
2635 lleft = linterp_exec(c, b->left, <ype);
2636 right = interp_exec(c, b->right, &rtype);
2638 mpz_tdiv_q(q, mpq_numref(right.num), mpq_denref(right.num));
2642 if (ltype->array.static_size)
2645 ptr = *(void**)lleft;
2646 rvtype = ltype->array.member;
2647 if (i >= 0 && i < ltype->array.size)
2648 lrv = ptr + i * rvtype->size;
2650 val_init(ltype->array.member, &rv); // UNSAFE
2655 lleft = linterp_exec(c, b->left, <ype);
2656 mpq_set_ui(rv.num, ltype->array.size, 1);
2664 A `struct` is a data-type that contains one or more other data-types.
2665 It differs from an array in that each member can be of a different
2666 type, and they are accessed by name rather than by number. Thus you
2667 cannot choose an element by calculation, you need to know what you
2670 The language makes no promises about how a given structure will be
2671 stored in memory - it is free to rearrange fields to suit whatever
2672 criteria seems important.
2674 Structs are declared separately from program code - they cannot be
2675 declared in-line in a variable declaration like arrays can. A struct
2676 is given a name and this name is used to identify the type - the name
2677 is not prefixed by the word `struct` as it would be in C.
2679 Structs are only treated as the same if they have the same name.
2680 Simply having the same fields in the same order is not enough. This
2681 might change once we can create structure initializers from a list of
2684 Each component datum is identified much like a variable is declared,
2685 with a name, one or two colons, and a type. The type cannot be omitted
2686 as there is no opportunity to deduce the type from usage. An initial
2687 value can be given following an equals sign, so
2689 ##### Example: a struct type
2695 would declare a type called "complex" which has two number fields,
2696 each initialised to zero.
2698 Struct will need to be declared separately from the code that uses
2699 them, so we will need to be able to print out the declaration of a
2700 struct when reprinting the whole program. So a `print_type_decl` type
2701 function will be needed.
2703 ###### type union fields
2712 } *fields; // This is created when field_list is analysed.
2714 struct fieldlist *prev;
2717 } *field_list; // This is created during parsing
2720 ###### type functions
2721 void (*print_type_decl)(struct type *type, FILE *f);
2722 struct type *(*fieldref)(struct type *t, struct parse_context *c,
2723 struct fieldref *f, struct value **vp);
2725 ###### value functions
2727 static void structure_init(struct type *type, struct value *val)
2731 for (i = 0; i < type->structure.nfields; i++) {
2733 v = (void*) val->ptr + type->structure.fields[i].offset;
2734 if (type->structure.fields[i].init)
2735 dup_value(type->structure.fields[i].type,
2736 type->structure.fields[i].init,
2739 val_init(type->structure.fields[i].type, v);
2743 static void structure_free(struct type *type, struct value *val)
2747 for (i = 0; i < type->structure.nfields; i++) {
2749 v = (void*)val->ptr + type->structure.fields[i].offset;
2750 free_value(type->structure.fields[i].type, v);
2754 static void free_fieldlist(struct fieldlist *f)
2758 free_fieldlist(f->prev);
2763 static void structure_free_type(struct type *t)
2766 for (i = 0; i < t->structure.nfields; i++)
2767 if (t->structure.fields[i].init) {
2768 free_value(t->structure.fields[i].type,
2769 t->structure.fields[i].init);
2771 free(t->structure.fields);
2772 free_fieldlist(t->structure.field_list);
2775 static int structure_prepare_type(struct parse_context *c,
2776 struct type *t, int parse_time)
2779 struct fieldlist *f;
2781 if (!parse_time || t->structure.fields)
2784 for (f = t->structure.field_list; f; f=f->prev) {
2788 if (f->f.type->size <= 0)
2790 if (f->f.type->prepare_type)
2791 f->f.type->prepare_type(c, f->f.type, parse_time);
2793 if (f->init == NULL)
2797 propagate_types(f->init, c, &perr, f->f.type, 0);
2798 } while (perr & Eretry);
2800 c->parse_error += 1; // NOTEST
2803 t->structure.nfields = cnt;
2804 t->structure.fields = calloc(cnt, sizeof(struct field));
2805 f = t->structure.field_list;
2807 int a = f->f.type->align;
2809 t->structure.fields[cnt] = f->f;
2810 if (t->size & (a-1))
2811 t->size = (t->size | (a-1)) + 1;
2812 t->structure.fields[cnt].offset = t->size;
2813 t->size += ((f->f.type->size - 1) | (a-1)) + 1;
2817 if (f->init && !c->parse_error) {
2818 struct value vl = interp_exec(c, f->init, NULL);
2819 t->structure.fields[cnt].init =
2820 global_alloc(c, f->f.type, NULL, &vl);
2828 static int find_struct_index(struct type *type, struct text field)
2831 for (i = 0; i < type->structure.nfields; i++)
2832 if (text_cmp(type->structure.fields[i].name, field) == 0)
2834 return IndexInvalid;
2837 static struct type *structure_fieldref(struct type *t, struct parse_context *c,
2838 struct fieldref *f, struct value **vp)
2840 if (f->index == IndexUnknown) {
2841 f->index = find_struct_index(t, f->name);
2843 type_err(c, "error: cannot find requested field in %1",
2844 f->left, t, 0, NULL);
2849 struct value *v = *vp;
2850 v = (void*)v->ptr + t->structure.fields[f->index].offset;
2853 return t->structure.fields[f->index].type;
2856 static struct type structure_prototype = {
2857 .init = structure_init,
2858 .free = structure_free,
2859 .free_type = structure_free_type,
2860 .print_type_decl = structure_print_type,
2861 .prepare_type = structure_prepare_type,
2862 .fieldref = structure_fieldref,
2875 enum { IndexUnknown = -1, IndexInvalid = -2 };
2877 ###### free exec cases
2879 free_exec(cast(fieldref, e)->left);
2883 ###### declare terminals
2888 | Term . IDENTIFIER ${ {
2889 struct fieldref *fr = new_pos(fieldref, $2);
2892 fr->index = IndexUnknown;
2896 ###### print exec cases
2900 struct fieldref *f = cast(fieldref, e);
2901 print_exec(f->left, -1, bracket);
2902 printf(".%.*s", f->name.len, f->name.txt);
2906 ###### propagate exec cases
2910 struct fieldref *f = cast(fieldref, prog);
2911 struct type *st = propagate_types(f->left, c, perr, NULL, 0);
2913 if (!st || !st->fieldref)
2914 type_err(c, "error: field reference on %1 is not supported",
2915 f->left, st, 0, NULL);
2917 t = st->fieldref(st, c, f, NULL);
2918 if (t && !type_compat(type, t, rules))
2919 type_err(c, "error: have %1 but need %2", prog,
2926 ###### interp exec cases
2929 struct fieldref *f = cast(fieldref, e);
2931 struct value *lleft = linterp_exec(c, f->left, <ype);
2933 rvtype = ltype->fieldref(ltype, c, f, &lrv);
2937 ###### top level grammar
2939 StructName -> IDENTIFIER ${ {
2940 struct type *t = find_type(c, $ID.txt);
2942 if (t && t->size >= 0) {
2943 tok_err(c, "error: type already declared", &$ID);
2944 tok_err(c, "info: this is location of declartion", &t->first_use);
2948 t = add_type(c, $ID.txt, NULL);
2953 DeclareStruct -> struct StructName FieldBlock Newlines ${ {
2954 struct type *t = $<SN;
2955 struct type tmp = *t;
2957 *t = structure_prototype;
2960 t->first_use = tmp.first_use;
2962 t->structure.field_list = $<FB;
2966 FieldBlock -> { IN OptNL FieldLines OUT OptNL } ${ $0 = $<FL; }$
2967 | { SimpleFieldList } ${ $0 = $<SFL; }$
2968 | IN OptNL FieldLines OUT ${ $0 = $<FL; }$
2969 | SimpleFieldList EOL ${ $0 = $<SFL; }$
2971 FieldLines -> SimpleFieldList Newlines ${ $0 = $<SFL; }$
2972 | FieldLines SimpleFieldList Newlines ${ {
2973 struct fieldlist *f = $<SFL;
2984 SimpleFieldList -> Field ${ $0 = $<F; }$
2985 | SimpleFieldList ; Field ${
2989 | SimpleFieldList ; ${
2992 | ERROR ${ tok_err(c, "Syntax error in struct field", &$1); }$
2994 Field -> IDENTIFIER : Type = Expression ${ {
2995 $0 = calloc(1, sizeof(struct fieldlist));
2996 $0->f.name = $ID.txt;
2997 $0->f.type = $<Type;
3001 | IDENTIFIER : Type ${
3002 $0 = calloc(1, sizeof(struct fieldlist));
3003 $0->f.name = $ID.txt;
3004 $0->f.type = $<Type;
3007 ###### forward decls
3008 static void structure_print_type(struct type *t, FILE *f);
3010 ###### value functions
3011 static void structure_print_type(struct type *t, FILE *f)
3015 fprintf(f, "struct %.*s\n", t->name.len, t->name.txt);
3017 for (i = 0; i < t->structure.nfields; i++) {
3018 struct field *fl = t->structure.fields + i;
3019 fprintf(f, " %.*s : ", fl->name.len, fl->name.txt);
3020 type_print(fl->type, f);
3021 if (fl->type->print && fl->init) {
3023 if (fl->type == Tstr)
3025 print_value(fl->type, fl->init, f);
3026 if (fl->type == Tstr)
3033 ###### print type decls
3038 while (target != 0) {
3040 for (t = context.typelist; t ; t=t->next)
3041 if (!t->anon && t->print_type_decl &&
3051 t->print_type_decl(t, stdout);
3059 References, or pointers, are values that refer to another value. They
3060 can only refer to a `struct`, though as a struct can embed anything they
3061 can effectively refer to anything.
3063 References are potentially dangerous as they might refer to some
3064 variable which no longer exists - either because a stack frame
3065 containing it has been discarded or because the value was allocated on
3066 the heap and has now been free. Ocean does not yet provide any
3067 protection against these problems. It will in due course.
3069 With references comes the opportunity and the need to explicitly
3070 allocate values on the "heap" and to free them. We currently provide
3071 fairly basic support for this.
3073 Reference make use of the `@` symbol in various ways. A type that starts
3074 with `@` is a reference to whatever follows. A reference value
3075 followed by an `@` acts as the referred value, though the `@` is often
3076 not needed. Finally, an expression that starts with `@` is a special
3077 reference related expression. Some examples might help.
3079 ##### Example: Reference examples
3086 bar.number = 23; bar.string = "hello"
3097 Obviously this is very contrived. `ref` is a reference to a `foo` which
3098 is initially set to refer to the value stored in `bar` - no extra syntax
3099 is needed to "Take the address of" `bar` - the fact that `ref` is a
3100 reference means that only the address make sense.
3102 When `ref.a` is accessed, that is whatever value is stored in `bar.a`.
3103 The same syntax is used for accessing fields both in structs and in
3104 references to structs. It would be correct to use `ref@.a`, but not
3107 `@new()` creates an object of whatever type is needed for the program
3108 to by type-correct. In future iterations of Ocean, arguments a
3109 constructor will access arguments, so the the syntax now looks like a
3110 function call. `@free` can be assigned any reference that was returned
3111 by `@new()`, and it will be freed. `@nil` is a value of whatever
3112 reference type is appropriate, and is stable and never the address of
3113 anything in the heap or on the stack. A reference can be assigned
3114 `@nil` or compared against that value.
3116 ###### declare terminals
3119 ###### type union fields
3122 struct type *referent;
3125 ###### value union fields
3128 ###### value functions
3130 static void reference_print_type(struct type *t, FILE *f)
3133 type_print(t->reference.referent, f);
3136 static int reference_cmp(struct type *tl, struct type *tr,
3137 struct value *left, struct value *right)
3139 return left->ref == right->ref ? 0 : 1;
3142 static void reference_dup(struct type *t,
3143 struct value *vold, struct value *vnew)
3145 vnew->ref = vold->ref;
3148 static void reference_free(struct type *t, struct value *v)
3150 /* Nothing to do here */
3153 static int reference_compat(struct type *require, struct type *have,
3154 enum val_rules rules)
3157 if (require->reference.referent == have)
3159 if (have->compat != require->compat)
3161 if (have->reference.referent != require->reference.referent)
3166 static int reference_test(struct type *type, struct value *val)
3168 return val->ref != NULL;
3171 static struct type *reference_fieldref(struct type *t, struct parse_context *c,
3172 struct fieldref *f, struct value **vp)
3174 struct type *rt = t->reference.referent;
3179 return rt->fieldref(rt, c, f, vp);
3181 type_err(c, "error: field reference on %1 is not supported",
3182 f->left, rt, 0, NULL);
3186 static struct type reference_prototype = {
3187 .print_type = reference_print_type,
3188 .cmp_eq = reference_cmp,
3189 .dup = reference_dup,
3190 .test = reference_test,
3191 .free = reference_free,
3192 .compat = reference_compat,
3193 .fieldref = reference_fieldref,
3194 .size = sizeof(void*),
3195 .align = sizeof(void*),
3201 struct type *t = find_type(c, $ID.txt);
3203 t = add_type(c, $ID.txt, NULL);
3206 $0 = find_anon_type(c, &reference_prototype, "@%.*s",
3207 $ID.txt.len, $ID.txt.txt);
3208 $0->reference.referent = t;
3211 ###### core functions
3212 static int text_is(struct text t, char *s)
3214 return (strlen(s) == t.len &&
3215 strncmp(s, t.txt, t.len) == 0);
3224 enum ref_func { RefNew, RefFree, RefNil } action;
3225 struct type *reftype;
3229 ###### SimpleStatement Grammar
3231 | @ IDENTIFIER = Expression ${ {
3232 struct ref *r = new_pos(ref, $ID);
3234 if (!text_is($ID.txt, "free"))
3235 tok_err(c, "error: only \"@free\" makes sense here",
3239 r->action = RefFree;
3243 ###### expression grammar
3244 | @ IDENTIFIER ( ) ${
3245 // Only 'new' valid here
3246 if (!text_is($ID.txt, "new")) {
3247 tok_err(c, "error: Only reference function is \"@new()\"",
3250 struct ref *r = new_pos(ref,$ID);
3256 // Only 'nil' valid here
3257 if (!text_is($ID.txt, "nil")) {
3258 tok_err(c, "error: Only reference value is \"@nil\"",
3261 struct ref *r = new_pos(ref,$ID);
3267 ###### print exec cases
3269 struct ref *r = cast(ref, e);
3270 switch (r->action) {
3272 printf("@new()"); break;
3274 printf("@nil"); break;
3276 do_indent(indent, "@free = ");
3277 print_exec(r->right, indent, bracket);
3283 ###### propagate exec cases
3285 struct ref *r = cast(ref, prog);
3286 switch (r->action) {
3288 if (type && type->free != reference_free) {
3289 type_err(c, "error: @new() can only be used with references, not %1",
3290 prog, type, 0, NULL);
3293 if (type && !r->reftype) {
3300 if (type && type->free != reference_free)
3301 type_err(c, "error: @nil can only be used with reference, not %1",
3302 prog, type, 0, NULL);
3303 if (type && !r->reftype) {
3310 t = propagate_types(r->right, c, perr_local, NULL, 0);
3311 if (t && t->free != reference_free)
3312 type_err(c, "error: @free can only be assigned a reference, not %1",
3321 ###### interp exec cases
3323 struct ref *r = cast(ref, e);
3324 switch (r->action) {
3327 rv.ref = calloc(1, r->reftype->reference.referent->size);
3328 rvtype = r->reftype;
3332 rvtype = r->reftype;
3335 rv = interp_exec(c, r->right, &rvtype);
3336 free_value(rvtype->reference.referent, rv.ref);
3344 ###### free exec cases
3346 struct ref *r = cast(ref, e);
3347 free_exec(r->right);
3352 ###### Expressions: dereference
3360 struct binode *b = new(binode);
3366 ###### print binode cases
3368 print_exec(b->left, -1, bracket);
3372 print_exec(b->left, -1, bracket);
3375 ###### propagate binode cases
3377 /* left must be a reference, and we return what it refers to */
3378 /* FIXME how can I pass the expected type down? */
3379 t = propagate_types(b->left, c, perr, NULL, 0);
3381 if (!t || t->free != reference_free)
3382 type_err(c, "error: Cannot dereference %1", b, t, 0, NULL);
3384 return t->reference.referent;
3388 /* left must be lval, we create reference to it */
3389 if (!type || type->free != reference_free)
3390 t = propagate_types(b->left, c, perr, type, 0); // NOTEST impossible
3392 t = propagate_types(b->left, c, perr,
3393 type->reference.referent, 0);
3395 t = find_anon_type(c, &reference_prototype, "@%.*s",
3396 t->name.len, t->name.txt);
3399 ###### interp binode cases
3401 left = interp_exec(c, b->left, <ype);
3403 rvtype = ltype->reference.referent;
3407 rv.ref = linterp_exec(c, b->left, &rvtype);
3408 rvtype = find_anon_type(c, &reference_prototype, "@%.*s",
3409 rvtype->name.len, rvtype->name.txt);
3415 A function is a chunk of code which can be passed parameters and can
3416 return results. Each function has a type which includes the set of
3417 parameters and the return value. As yet these types cannot be declared
3418 separately from the function itself.
3420 The parameters can be specified either in parentheses as a ';' separated
3423 ##### Example: function 1
3425 func main(av:[ac::number]string; env:[envc::number]string)
3428 or as an indented list of one parameter per line (though each line can
3429 be a ';' separated list)
3431 ##### Example: function 2
3434 argv:[argc::number]string
3435 env:[envc::number]string
3439 In the first case a return type can follow the parentheses after a colon,
3440 in the second it is given on a line starting with the word `return`.
3442 ##### Example: functions that return
3444 func add(a:number; b:number): number
3454 Rather than returning a type, the function can specify a set of local
3455 variables to return as a struct. The values of these variables when the
3456 function exits will be provided to the caller. For this the return type
3457 is replaced with a block of result declarations, either in parentheses
3458 or bracketed by `return` and `do`.
3460 ##### Example: functions returning multiple variables
3462 func to_cartesian(rho:number; theta:number):(x:number; y:number)
3475 For constructing the lists we use a `List` binode, which will be
3476 further detailed when Expression Lists are introduced.
3478 ###### type union fields
3481 struct binode *params;
3482 struct type *return_type;
3483 struct variable *scope;
3484 int inline_result; // return value is at start of 'local'
3488 ###### value union fields
3489 struct exec *function;
3491 ###### type functions
3492 void (*check_args)(struct parse_context *c, enum prop_err *perr,
3493 struct type *require, struct exec *args);
3495 ###### value functions
3497 static void function_free(struct type *type, struct value *val)
3499 free_exec(val->function);
3500 val->function = NULL;
3503 static int function_compat(struct type *require, struct type *have,
3504 enum val_rules rules)
3506 // FIXME can I do anything here yet?
3510 static struct exec *take_addr(struct exec *e)
3512 struct binode *rv = new(binode);
3518 static void function_check_args(struct parse_context *c, enum prop_err *perr,
3519 struct type *require, struct exec *args)
3521 /* This should be 'compat', but we don't have a 'tuple' type to
3522 * hold the type of 'args'
3524 struct binode *arg = cast(binode, args);
3525 struct binode *param = require->function.params;
3528 struct var *pv = cast(var, param->left);
3529 struct type *t = pv->var->type, *t2;
3531 type_err(c, "error: insufficient arguments to function.",
3532 args, NULL, 0, NULL);
3536 t2 = propagate_types(arg->left, c, perr, t, Rrefok);
3537 if (t->free == reference_free &&
3538 t->reference.referent == t2 &&
3540 arg->left = take_addr(arg->left);
3541 } else if (!(*perr & Efail) && !type_compat(t2, t, 0)) {
3542 type_err(c, "error: cannot pass rval when reference expected",
3543 arg->left, NULL, 0, NULL);
3545 param = cast(binode, param->right);
3546 arg = cast(binode, arg->right);
3549 type_err(c, "error: too many arguments to function.",
3550 args, NULL, 0, NULL);
3553 static void function_print(struct type *type, struct value *val, FILE *f)
3556 print_exec(val->function, 1, 0);
3559 static void function_print_type_decl(struct type *type, FILE *f)
3563 for (b = type->function.params; b; b = cast(binode, b->right)) {
3564 struct variable *v = cast(var, b->left)->var;
3565 fprintf(f, "%.*s%s", v->name->name.len, v->name->name.txt,
3566 v->constant ? "::" : ":");
3567 type_print(v->type, f);
3572 if (type->function.return_type != Tnone) {
3574 if (type->function.inline_result) {
3576 struct type *t = type->function.return_type;
3578 for (i = 0; i < t->structure.nfields; i++) {
3579 struct field *fl = t->structure.fields + i;
3582 fprintf(f, "%.*s:", fl->name.len, fl->name.txt);
3583 type_print(fl->type, f);
3587 type_print(type->function.return_type, f);
3591 static void function_free_type(struct type *t)
3593 free_exec(t->function.params);
3596 static struct type function_prototype = {
3597 .size = sizeof(void*),
3598 .align = sizeof(void*),
3599 .free = function_free,
3600 .compat = function_compat,
3601 .check_args = function_check_args,
3602 .print = function_print,
3603 .print_type_decl = function_print_type_decl,
3604 .free_type = function_free_type,
3607 ###### declare terminals
3617 FuncName -> IDENTIFIER ${ {
3618 struct variable *v = var_decl(c, $1.txt);
3619 struct var *e = new_pos(var, $1);
3626 v = var_ref(c, $1.txt);
3628 type_err(c, "error: function '%v' redeclared",
3630 type_err(c, "info: this is where '%v' was first declared",
3631 v->where_decl, NULL, 0, NULL);
3637 Args -> ArgsLine NEWLINE ${ $0 = $<AL; }$
3638 | Args ArgsLine NEWLINE ${ {
3639 struct binode *b = $<AL;
3640 struct binode **bp = &b;
3642 bp = (struct binode **)&(*bp)->left;
3647 ArgsLine -> ${ $0 = NULL; }$
3648 | Varlist ${ $0 = $<1; }$
3649 | Varlist ; ${ $0 = $<1; }$
3651 Varlist -> Varlist ; ArgDecl ${
3652 $0 = new_pos(binode, $2);
3665 ArgDecl -> IDENTIFIER : FormalType ${ {
3666 struct variable *v = var_decl(c, $ID.txt);
3667 $0 = new_pos(var, $ID);
3674 ##### Function calls
3676 A function call can appear either as an expression or as a statement.
3677 We use a new 'Funcall' binode type to link the function with a list of
3678 arguments, form with the 'List' nodes.
3680 We have already seen the "Term" which is how a function call can appear
3681 in an expression. To parse a function call into a statement we include
3682 it in the "SimpleStatement Grammar" which will be described later.
3688 | Term ( ExpressionList ) ${ {
3689 struct binode *b = new(binode);
3692 b->right = reorder_bilist($<EL);
3696 struct binode *b = new(binode);
3703 ###### SimpleStatement Grammar
3705 | Term ( ExpressionList ) ${ {
3706 struct binode *b = new(binode);
3709 b->right = reorder_bilist($<EL);
3713 ###### print binode cases
3716 do_indent(indent, "");
3717 print_exec(b->left, -1, bracket);
3719 for (b = cast(binode, b->right); b; b = cast(binode, b->right)) {
3722 print_exec(b->left, -1, bracket);
3732 ###### propagate binode cases
3735 /* Every arg must match formal parameter, and result
3736 * is return type of function
3738 struct binode *args = cast(binode, b->right);
3739 struct var *v = cast(var, b->left);
3741 if (!v->var->type || v->var->type->check_args == NULL) {
3742 type_err(c, "error: attempt to call a non-function.",
3743 prog, NULL, 0, NULL);
3747 v->var->type->check_args(c, perr_local, v->var->type, args);
3748 if (v->var->type->function.inline_result)
3751 return v->var->type->function.return_type;
3754 ###### interp binode cases
3757 struct var *v = cast(var, b->left);
3758 struct type *t = v->var->type;
3759 void *oldlocal = c->local;
3760 int old_size = c->local_size;
3761 void *local = calloc(1, t->function.local_size);
3762 struct value *fbody = var_value(c, v->var);
3763 struct binode *arg = cast(binode, b->right);
3764 struct binode *param = t->function.params;
3767 struct var *pv = cast(var, param->left);
3768 struct type *vtype = NULL;
3769 struct value val = interp_exec(c, arg->left, &vtype);
3771 c->local = local; c->local_size = t->function.local_size;
3772 lval = var_value(c, pv->var);
3773 c->local = oldlocal; c->local_size = old_size;
3774 memcpy(lval, &val, vtype->size);
3775 param = cast(binode, param->right);
3776 arg = cast(binode, arg->right);
3778 c->local = local; c->local_size = t->function.local_size;
3779 if (t->function.inline_result && dtype) {
3780 _interp_exec(c, fbody->function, NULL, NULL);
3781 memcpy(dest, local, dtype->size);
3782 rvtype = ret.type = NULL;
3784 rv = interp_exec(c, fbody->function, &rvtype);
3785 c->local = oldlocal; c->local_size = old_size;
3790 ## Complex executables: statements and expressions
3792 Now that we have types and values and variables and most of the basic
3793 Terms which provide access to these, we can explore the more complex
3794 code that combine all of these to get useful work done. Specifically
3795 statements and expressions.
3797 Expressions are various combinations of Terms. We will use operator
3798 precedence to ensure correct parsing. The simplest Expression is just a
3799 Term - others will follow.
3804 Expression -> Term ${ $0 = $<Term; }$
3805 ## expression grammar
3807 ### Expressions: Conditional
3809 Our first user of the `binode` will be conditional expressions, which
3810 is a bit odd as they actually have three components. That will be
3811 handled by having 2 binodes for each expression. The conditional
3812 expression is the lowest precedence operator which is why we define it
3813 first - to start the precedence list.
3815 Conditional expressions are of the form "value `if` condition `else`
3816 other_value". They associate to the right, so everything to the right
3817 of `else` is part of an else value, while only a higher-precedence to
3818 the left of `if` is the if values. Between `if` and `else` there is no
3819 room for ambiguity, so a full conditional expression is allowed in
3825 ###### declare terminals
3829 ###### expression grammar
3831 | Expression if Expression else Expression $$ifelse ${ {
3832 struct binode *b1 = new(binode);
3833 struct binode *b2 = new(binode);
3843 ###### print binode cases
3846 b2 = cast(binode, b->right);
3847 if (bracket) printf("(");
3848 print_exec(b2->left, -1, bracket);
3850 print_exec(b->left, -1, bracket);
3852 print_exec(b2->right, -1, bracket);
3853 if (bracket) printf(")");
3856 ###### propagate binode cases
3859 /* cond must be Tbool, others must match */
3860 struct binode *b2 = cast(binode, b->right);
3863 propagate_types(b->left, c, perr_local, Tbool, 0);
3864 t = propagate_types(b2->left, c, perr, type, 0);
3865 t2 = propagate_types(b2->right, c, perr, type ?: t, 0);
3869 ###### interp binode cases
3872 struct binode *b2 = cast(binode, b->right);
3873 left = interp_exec(c, b->left, <ype);
3875 rv = interp_exec(c, b2->left, &rvtype);
3877 rv = interp_exec(c, b2->right, &rvtype);
3883 We take a brief detour, now that we have expressions, to describe lists
3884 of expressions. These will be needed for function parameters and
3885 possibly other situations. They seem generic enough to introduce here
3886 to be used elsewhere.
3888 And ExpressionList will use the `List` type of `binode`, building up at
3889 the end. And place where they are used will probably call
3890 `reorder_bilist()` to get a more normal first/next arrangement.
3892 ###### declare terminals
3895 `List` execs have no implicit semantics, so they are never propagated or
3896 interpreted. The can be printed as a comma separate list, which is how
3897 they are parsed. Note they are also used for function formal parameter
3898 lists. In that case a separate function is used to print them.
3900 ###### print binode cases
3904 print_exec(b->left, -1, bracket);
3907 b = cast(binode, b->right);
3911 ###### propagate binode cases
3912 case List: abort(); // NOTEST
3913 ###### interp binode cases
3914 case List: abort(); // NOTEST
3919 ExpressionList -> ExpressionList , Expression ${
3932 ### Expressions: Boolean
3934 The next class of expressions to use the `binode` will be Boolean
3935 expressions. `and` and `or` are short-circuit operators that don't
3936 evaluate the second expression if not necessary.
3943 ###### declare terminals
3948 ###### expression grammar
3949 | Expression or Expression ${ {
3950 struct binode *b = new(binode);
3956 | Expression and Expression ${ {
3957 struct binode *b = new(binode);
3963 | not Expression ${ {
3964 struct binode *b = new(binode);
3970 ###### print binode cases
3972 if (bracket) printf("(");
3973 print_exec(b->left, -1, bracket);
3975 print_exec(b->right, -1, bracket);
3976 if (bracket) printf(")");
3979 if (bracket) printf("(");
3980 print_exec(b->left, -1, bracket);
3982 print_exec(b->right, -1, bracket);
3983 if (bracket) printf(")");
3986 if (bracket) printf("(");
3988 print_exec(b->right, -1, bracket);
3989 if (bracket) printf(")");
3992 ###### propagate binode cases
3996 /* both must be Tbool, result is Tbool */
3997 propagate_types(b->left, c, perr, Tbool, 0);
3998 propagate_types(b->right, c, perr, Tbool, 0);
3999 if (type && type != Tbool)
4000 type_err(c, "error: %1 operation found where %2 expected", prog,
4005 ###### interp binode cases
4007 rv = interp_exec(c, b->left, &rvtype);
4009 rv = interp_exec(c, b->right, NULL);
4012 rv = interp_exec(c, b->left, &rvtype);
4014 rv = interp_exec(c, b->right, NULL);
4017 rv = interp_exec(c, b->right, &rvtype);
4021 ### Expressions: Comparison
4023 Of slightly higher precedence that Boolean expressions are Comparisons.
4024 A comparison takes arguments of any comparable type, but the two types
4027 To simplify the parsing we introduce an `eop` which can record an
4028 expression operator, and the `CMPop` non-terminal will match one of them.
4035 ###### ast functions
4036 static void free_eop(struct eop *e)
4050 ###### declare terminals
4051 $LEFT < > <= >= == != CMPop
4053 ###### expression grammar
4054 | Expression CMPop Expression ${ {
4055 struct binode *b = new(binode);
4065 CMPop -> < ${ $0.op = Less; }$
4066 | > ${ $0.op = Gtr; }$
4067 | <= ${ $0.op = LessEq; }$
4068 | >= ${ $0.op = GtrEq; }$
4069 | == ${ $0.op = Eql; }$
4070 | != ${ $0.op = NEql; }$
4072 ###### print binode cases
4080 if (bracket) printf("(");
4081 print_exec(b->left, -1, bracket);
4083 case Less: printf(" < "); break;
4084 case LessEq: printf(" <= "); break;
4085 case Gtr: printf(" > "); break;
4086 case GtrEq: printf(" >= "); break;
4087 case Eql: printf(" == "); break;
4088 case NEql: printf(" != "); break;
4089 default: abort(); // NOTEST
4091 print_exec(b->right, -1, bracket);
4092 if (bracket) printf(")");
4095 ###### propagate binode cases
4102 /* Both must match but not be labels, result is Tbool */
4103 t = propagate_types(b->left, c, perr, NULL, 0);
4105 propagate_types(b->right, c, perr, t, 0);
4107 t = propagate_types(b->right, c, perr, NULL, 0); // NOTEST
4109 t = propagate_types(b->left, c, perr, t, 0); // NOTEST
4111 if (!type_compat(type, Tbool, 0))
4112 type_err(c, "error: Comparison returns %1 but %2 expected", prog,
4113 Tbool, rules, type);
4117 ###### interp binode cases
4126 left = interp_exec(c, b->left, <ype);
4127 right = interp_exec(c, b->right, &rtype);
4128 cmp = value_cmp(ltype, rtype, &left, &right);
4131 case Less: rv.bool = cmp < 0; break;
4132 case LessEq: rv.bool = cmp <= 0; break;
4133 case Gtr: rv.bool = cmp > 0; break;
4134 case GtrEq: rv.bool = cmp >= 0; break;
4135 case Eql: rv.bool = cmp == 0; break;
4136 case NEql: rv.bool = cmp != 0; break;
4137 default: rv.bool = 0; break; // NOTEST
4142 ### Expressions: Arithmetic etc.
4144 The remaining expressions with the highest precedence are arithmetic,
4145 string concatenation, string conversion, and testing. String concatenation
4146 (`++`) has the same precedence as multiplication and division, but lower
4149 Testing comes in two forms. A single question mark (`?`) is a uniary
4150 operator which converts come types into Boolean. The general meaning is
4151 "is this a value value" and there will be more uses as the language
4152 develops. A double questionmark (`??`) is a binary operator (Choose),
4153 with same precedence as multiplication, which returns the LHS if it
4154 tests successfully, else returns the RHS.
4156 String conversion is a temporary feature until I get a better type
4157 system. `$` is a prefix operator which expects a string and returns
4160 `+` and `-` are both infix and prefix operations (where they are
4161 absolute value and negation). These have different operator names.
4163 We also have a 'Bracket' operator which records where parentheses were
4164 found. This makes it easy to reproduce these when printing. Possibly I
4165 should only insert brackets were needed for precedence. Putting
4166 parentheses around an expression converts it into a Term,
4172 Absolute, Negate, Test,
4176 ###### declare terminals
4178 $LEFT * / % ++ ?? Top
4182 ###### expression grammar
4183 | Expression Eop Expression ${ {
4184 struct binode *b = new(binode);
4191 | Expression Top Expression ${ {
4192 struct binode *b = new(binode);
4199 | Uop Expression ${ {
4200 struct binode *b = new(binode);
4208 | ( Expression ) ${ {
4209 struct binode *b = new_pos(binode, $1);
4218 Eop -> + ${ $0.op = Plus; }$
4219 | - ${ $0.op = Minus; }$
4221 Uop -> + ${ $0.op = Absolute; }$
4222 | - ${ $0.op = Negate; }$
4223 | $ ${ $0.op = StringConv; }$
4224 | ? ${ $0.op = Test; }$
4226 Top -> * ${ $0.op = Times; }$
4227 | / ${ $0.op = Divide; }$
4228 | % ${ $0.op = Rem; }$
4229 | ++ ${ $0.op = Concat; }$
4230 | ?? ${ $0.op = Choose; }$
4232 ###### print binode cases
4240 if (bracket) printf("(");
4241 print_exec(b->left, indent, bracket);
4243 case Plus: fputs(" + ", stdout); break;
4244 case Minus: fputs(" - ", stdout); break;
4245 case Times: fputs(" * ", stdout); break;
4246 case Divide: fputs(" / ", stdout); break;
4247 case Rem: fputs(" % ", stdout); break;
4248 case Concat: fputs(" ++ ", stdout); break;
4249 case Choose: fputs(" ?? ", stdout); break;
4250 default: abort(); // NOTEST
4252 print_exec(b->right, indent, bracket);
4253 if (bracket) printf(")");
4259 if (bracket) printf("(");
4261 case Absolute: fputs("+", stdout); break;
4262 case Negate: fputs("-", stdout); break;
4263 case StringConv: fputs("$", stdout); break;
4264 case Test: fputs("?", stdout); break;
4265 default: abort(); // NOTEST
4267 print_exec(b->right, indent, bracket);
4268 if (bracket) printf(")");
4271 /* Avoid double brackets... */
4272 if (!bracket) printf("(");
4273 print_exec(b->right, indent, bracket);
4274 if (!bracket) printf(")");
4277 ###### propagate binode cases
4283 /* both must be numbers, result is Tnum */
4286 /* as propagate_types ignores a NULL,
4287 * unary ops fit here too */
4288 propagate_types(b->left, c, perr, Tnum, 0);
4289 propagate_types(b->right, c, perr, Tnum, 0);
4290 if (!type_compat(type, Tnum, 0))
4291 type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
4297 /* both must be Tstr, result is Tstr */
4298 propagate_types(b->left, c, perr, Tstr, 0);
4299 propagate_types(b->right, c, perr, Tstr, 0);
4300 if (!type_compat(type, Tstr, 0))
4301 type_err(c, "error: Concat returns %1 but %2 expected", prog,
4307 /* op must be string, result is number */
4308 propagate_types(b->left, c, perr, Tstr, 0);
4309 if (!type_compat(type, Tnum, 0))
4311 "error: Can only convert string to number, not %1",
4312 prog, type, 0, NULL);
4317 /* LHS must support ->test, result is Tbool */
4318 t = propagate_types(b->right, c, perr, NULL, 0);
4320 type_err(c, "error: '?' requires a testable value, not %1",
4326 /* LHS and RHS must match and are returned. Must support
4329 t = propagate_types(b->left, c, perr, type, rules);
4330 t = propagate_types(b->right, c, perr, t, rules);
4331 if (t && t->test == NULL)
4332 type_err(c, "error: \"??\" requires a testable value, not %1",
4338 return propagate_types(b->right, c, perr, type, rules);
4340 ###### interp binode cases
4343 rv = interp_exec(c, b->left, &rvtype);
4344 right = interp_exec(c, b->right, &rtype);
4345 mpq_add(rv.num, rv.num, right.num);
4348 rv = interp_exec(c, b->left, &rvtype);
4349 right = interp_exec(c, b->right, &rtype);
4350 mpq_sub(rv.num, rv.num, right.num);
4353 rv = interp_exec(c, b->left, &rvtype);
4354 right = interp_exec(c, b->right, &rtype);
4355 mpq_mul(rv.num, rv.num, right.num);
4358 rv = interp_exec(c, b->left, &rvtype);
4359 right = interp_exec(c, b->right, &rtype);
4360 mpq_div(rv.num, rv.num, right.num);
4365 left = interp_exec(c, b->left, <ype);
4366 right = interp_exec(c, b->right, &rtype);
4367 mpz_init(l); mpz_init(r); mpz_init(rem);
4368 mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
4369 mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
4370 mpz_tdiv_r(rem, l, r);
4371 val_init(Tnum, &rv);
4372 mpq_set_z(rv.num, rem);
4373 mpz_clear(r); mpz_clear(l); mpz_clear(rem);
4378 rv = interp_exec(c, b->right, &rvtype);
4379 mpq_neg(rv.num, rv.num);
4382 rv = interp_exec(c, b->right, &rvtype);
4383 mpq_abs(rv.num, rv.num);
4386 rv = interp_exec(c, b->right, &rvtype);
4389 left = interp_exec(c, b->left, <ype);
4390 right = interp_exec(c, b->right, &rtype);
4392 rv.str = text_join(left.str, right.str);
4395 right = interp_exec(c, b->right, &rvtype);
4399 struct text tx = right.str;
4402 if (tx.txt[0] == '-') {
4407 if (number_parse(rv.num, tail, tx) == 0)
4410 mpq_neg(rv.num, rv.num);
4412 printf("Unsupported suffix: %.*s\n", tx.len, tx.txt);
4416 right = interp_exec(c, b->right, &rtype);
4418 rv.bool = !!rtype->test(rtype, &right);
4421 left = interp_exec(c, b->left, <ype);
4422 if (ltype->test(ltype, &left)) {
4427 rv = interp_exec(c, b->right, &rvtype);
4430 ###### value functions
4432 static struct text text_join(struct text a, struct text b)
4435 rv.len = a.len + b.len;
4436 rv.txt = malloc(rv.len);
4437 memcpy(rv.txt, a.txt, a.len);
4438 memcpy(rv.txt+a.len, b.txt, b.len);
4442 ### Blocks, Statements, and Statement lists.
4444 Now that we have expressions out of the way we need to turn to
4445 statements. There are simple statements and more complex statements.
4446 Simple statements do not contain (syntactic) newlines, complex statements do.
4448 Statements often come in sequences and we have corresponding simple
4449 statement lists and complex statement lists.
4450 The former comprise only simple statements separated by semicolons.
4451 The later comprise complex statements and simple statement lists. They are
4452 separated by newlines. Thus the semicolon is only used to separate
4453 simple statements on the one line. This may be overly restrictive,
4454 but I'm not sure I ever want a complex statement to share a line with
4457 Note that a simple statement list can still use multiple lines if
4458 subsequent lines are indented, so
4460 ###### Example: wrapped simple statement list
4465 is a single simple statement list. This might allow room for
4466 confusion, so I'm not set on it yet.
4468 A simple statement list needs no extra syntax. A complex statement
4469 list has two syntactic forms. It can be enclosed in braces (much like
4470 C blocks), or it can be introduced by an indent and continue until an
4471 unindented newline (much like Python blocks). With this extra syntax
4472 it is referred to as a block.
4474 Note that a block does not have to include any newlines if it only
4475 contains simple statements. So both of:
4477 if condition: a=b; d=f
4479 if condition { a=b; print f }
4483 In either case the list is constructed from a `binode` list with
4484 `Block` as the operator. When parsing the list it is most convenient
4485 to append to the end, so a list is a list and a statement. When using
4486 the list it is more convenient to consider a list to be a statement
4487 and a list. So we need a function to re-order a list.
4488 `reorder_bilist` serves this purpose.
4490 The only stand-alone statement we introduce at this stage is `pass`
4491 which does nothing and is represented as a `NULL` pointer in a `Block`
4492 list. Other stand-alone statements will follow once the infrastructure
4495 As many statements will use binodes, we declare a binode pointer 'b' in
4496 the common header for all reductions to use.
4498 ###### Parser: reduce
4509 Block -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4510 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4511 | SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
4512 | SimpleStatements EOL ${ $0 = reorder_bilist($<SS);
4514 | IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
4516 OpenBlock -> OpenScope { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4517 | OpenScope { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4518 | OpenScope SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
4519 | OpenScope SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
4520 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
4522 UseBlock -> { IN OpenScope OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4523 | { OpenScope SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4524 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
4526 ColonBlock -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4527 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4528 | : SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
4529 | : SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
4530 | : IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
4532 Statementlist -> ComplexStatements ${ $0 = reorder_bilist($<CS); }$
4534 ComplexStatements -> ComplexStatements ComplexStatement ${
4536 $0 = $<1; // NOTEST - impossible
4544 | ComplexStatement ${
4546 $0 = NULL; // NOTEST - impossible
4556 ComplexStatement -> SimpleStatements Newlines ${
4557 $0 = reorder_bilist($<SS);
4559 | SimpleStatements ; Newlines ${
4560 $0 = reorder_bilist($<SS);
4562 ## ComplexStatement Grammar
4565 SimpleStatements -> SimpleStatements ; SimpleStatement ${
4571 | SimpleStatement ${
4580 SimpleStatement -> pass ${ $0 = NULL; }$
4581 | ERROR ${ tok_err(c, "Syntax error in statement", &$1); }$
4582 ## SimpleStatement Grammar
4584 ###### print binode cases
4586 // block, one per line
4587 if (b->left == NULL)
4588 do_indent(indent, "pass\n");
4590 print_exec(b->left, indent, bracket);
4592 print_exec(b->right, indent, bracket);
4595 ###### propagate binode cases
4598 /* If any statement returns something other than Tnone
4599 * or Tbool then all such must return same type.
4600 * As each statement may be Tnone or something else,
4601 * we must always pass NULL (unknown) down, otherwise an incorrect
4602 * error might occur. We never return Tnone unless it is
4607 for (e = b; e; e = cast(binode, e->right)) {
4608 *perr |= *perr_local;
4610 t = propagate_types(e->left, c, perr_local, NULL, rules);
4611 if ((rules & Rboolok) && (t == Tbool || t == Tnone))
4613 if (t == Tnone && e->right)
4614 /* Only the final statement *must* return a value
4622 type_err(c, "error: expected %1, found %2",
4623 e->left, type, rules, t);
4629 ###### interp binode cases
4631 while (rvtype == Tnone &&
4634 rv = interp_exec(c, b->left, &rvtype);
4635 b = cast(binode, b->right);
4639 ### The Print statement
4641 `print` is a simple statement that takes a comma-separated list of
4642 expressions and prints the values separated by spaces and terminated
4643 by a newline. No control of formatting is possible.
4645 `print` uses `ExpressionList` to collect the expressions and stores them
4646 on the left side of a `Print` binode unlessthere is a trailing comma
4647 when the list is stored on the `right` side and no trailing newline is
4653 ##### declare terminals
4656 ###### SimpleStatement Grammar
4658 | print ExpressionList ${
4659 $0 = b = new_pos(binode, $1);
4662 b->left = reorder_bilist($<EL);
4664 | print ExpressionList , ${ {
4665 $0 = b = new_pos(binode, $1);
4667 b->right = reorder_bilist($<EL);
4671 $0 = b = new_pos(binode, $1);
4677 ###### print binode cases
4680 do_indent(indent, "print");
4682 print_exec(b->right, -1, bracket);
4685 print_exec(b->left, -1, bracket);
4690 ###### propagate binode cases
4693 /* don't care but all must be consistent */
4695 b = cast(binode, b->left);
4697 b = cast(binode, b->right);
4699 propagate_types(b->left, c, perr_local, NULL, 0);
4700 b = cast(binode, b->right);
4704 ###### interp binode cases
4708 struct binode *b2 = cast(binode, b->left);
4710 b2 = cast(binode, b->right);
4711 for (; b2; b2 = cast(binode, b2->right)) {
4712 left = interp_exec(c, b2->left, <ype);
4713 print_value(ltype, &left, stdout);
4714 free_value(ltype, &left);
4718 if (b->right == NULL)
4724 ###### Assignment statement
4726 An assignment will assign a value to a variable, providing it hasn't
4727 been declared as a constant. The analysis phase ensures that the type
4728 will be correct so the interpreter just needs to perform the
4729 calculation. There is a form of assignment which declares a new
4730 variable as well as assigning a value. If a name is used before
4731 it is declared, it is assumed to be a global constant which are allowed to
4732 be declared at any time.
4738 ###### declare terminals
4741 ###### SimpleStatement Grammar
4742 | Term = Expression ${
4743 $0 = b= new(binode);
4748 | VariableDecl = Expression ${
4749 $0 = b= new(binode);
4756 if ($1->var->where_set == NULL) {
4758 "Variable declared with no type or value: %v",
4762 $0 = b = new(binode);
4769 ###### print binode cases
4772 do_indent(indent, "");
4773 print_exec(b->left, -1, bracket);
4775 print_exec(b->right, -1, bracket);
4782 struct variable *v = cast(var, b->left)->var;
4783 do_indent(indent, "");
4784 print_exec(b->left, -1, bracket);
4785 if (cast(var, b->left)->var->constant) {
4787 if (v->explicit_type) {
4788 type_print(v->type, stdout);
4793 if (v->explicit_type) {
4794 type_print(v->type, stdout);
4800 print_exec(b->right, -1, bracket);
4807 ###### propagate binode cases
4811 /* Both must match, or left may be ref and right an lval
4812 * Type must support 'dup',
4813 * For Assign, left must not be constant.
4816 *perr &= ~(Erval | Econst);
4817 t = propagate_types(b->left, c, perr, NULL, 0);
4822 struct type *t2 = propagate_types(b->right, c, perr_local,
4824 if (!t2 || t2 == t || (*perr_local & Efail))
4825 ; // No more effort needed
4826 else if (t->free == reference_free &&
4827 t->reference.referent == t2 &&
4828 !(*perr_local & Erval))
4829 b->right = take_addr(b->right);
4830 else if (t->free == reference_free &&
4831 t->reference.referent == t2 &&
4832 (*perr_local & Erval))
4833 type_err(c, "error: Cannot assign an rval to a reference.",
4836 t = propagate_types(b->right, c, perr_local, NULL, 0);
4838 propagate_types(b->left, c, perr, t, 0);
4841 type_err(c, "error: cannot assign to an rval", b,
4843 else if (b->op == Assign && (*perr & Econst)) {
4844 type_err(c, "error: Cannot assign to a constant: %v",
4845 b->left, NULL, 0, NULL);
4846 if (b->left->type == Xvar) {
4847 struct var *var = cast(var, b->left);
4848 struct variable *v = var->var;
4849 type_err(c, "info: name was defined as a constant here",
4850 v->where_decl, NULL, 0, NULL);
4853 if (t && t->dup == NULL && !(*perr_local & Emaycopy))
4854 type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
4855 if (b->left->type == Xvar && (*perr_local & Efail))
4856 type_err(c, "info: variable '%v' was set as %1 here.",
4857 cast(var, b->left)->var->where_set, t, rules, NULL);
4862 ###### interp binode cases
4865 lleft = linterp_exec(c, b->left, <ype);
4867 dinterp_exec(c, b->right, lleft, ltype, 1);
4873 struct variable *v = cast(var, b->left)->var;
4876 val = var_value(c, v);
4877 if (v->type->prepare_type)
4878 v->type->prepare_type(c, v->type, 0);
4880 val_init(v->type, val);
4882 dinterp_exec(c, b->right, val, v->type, 0);
4886 ### The `use` statement
4888 The `use` statement is the last "simple" statement. It is needed when a
4889 statement block can return a value. This includes the body of a
4890 function which has a return type, and the "condition" code blocks in
4891 `if`, `while`, and `switch` statements.
4896 ###### declare terminals
4899 ###### SimpleStatement Grammar
4901 $0 = b = new_pos(binode, $1);
4906 ###### print binode cases
4909 do_indent(indent, "use ");
4910 print_exec(b->right, -1, bracket);
4915 ###### propagate binode cases
4918 /* result matches value */
4919 return propagate_types(b->right, c, perr, type, 0);
4921 ###### interp binode cases
4924 rv = interp_exec(c, b->right, &rvtype);
4927 ### The Conditional Statement
4929 This is the biggy and currently the only complex statement. This
4930 subsumes `if`, `while`, `do/while`, `switch`, and some parts of `for`.
4931 It is comprised of a number of parts, all of which are optional though
4932 set combinations apply. Each part is (usually) a key word (`then` is
4933 sometimes optional) followed by either an expression or a code block,
4934 except the `casepart` which is a "key word and an expression" followed
4935 by a code block. The code-block option is valid for all parts and,
4936 where an expression is also allowed, the code block can use the `use`
4937 statement to report a value. If the code block does not report a value
4938 the effect is similar to reporting `True`.
4940 The `else` and `case` parts, as well as `then` when combined with
4941 `if`, can contain a `use` statement which will apply to some
4942 containing conditional statement. `for` parts, `do` parts and `then`
4943 parts used with `for` can never contain a `use`, except in some
4944 subordinate conditional statement.
4946 If there is a `forpart`, it is executed first, only once.
4947 If there is a `dopart`, then it is executed repeatedly providing
4948 always that the `condpart` or `cond`, if present, does not return a non-True
4949 value. `condpart` can fail to return any value if it simply executes
4950 to completion. This is treated the same as returning `True`.
4952 If there is a `thenpart` it will be executed whenever the `condpart`
4953 or `cond` returns True (or does not return any value), but this will happen
4954 *after* `dopart` (when present).
4956 If `elsepart` is present it will be executed at most once when the
4957 condition returns `False` or some value that isn't `True` and isn't
4958 matched by any `casepart`. If there are any `casepart`s, they will be
4959 executed when the condition returns a matching value.
4961 The particular sorts of values allowed in case parts has not yet been
4962 determined in the language design, so nothing is prohibited.
4964 The various blocks in this complex statement potentially provide scope
4965 for variables as described earlier. Each such block must include the
4966 "OpenScope" nonterminal before parsing the block, and must call
4967 `var_block_close()` when closing the block.
4969 The code following "`if`", "`switch`" and "`for`" does not get its own
4970 scope, but is in a scope covering the whole statement, so names
4971 declared there cannot be redeclared elsewhere. Similarly the
4972 condition following "`while`" is in a scope the covers the body
4973 ("`do`" part) of the loop, and which does not allow conditional scope
4974 extension. Code following "`then`" (both looping and non-looping),
4975 "`else`" and "`case`" each get their own local scope.
4977 The type requirements on the code block in a `whilepart` are quite
4978 unusal. It is allowed to return a value of some identifiable type, in
4979 which case the loop aborts and an appropriate `casepart` is run, or it
4980 can return a Boolean, in which case the loop either continues to the
4981 `dopart` (on `True`) or aborts and runs the `elsepart` (on `False`).
4982 This is different both from the `ifpart` code block which is expected to
4983 return a Boolean, or the `switchpart` code block which is expected to
4984 return the same type as the casepart values. The correct analysis of
4985 the type of the `whilepart` code block is the reason for the
4986 `Rboolok` flag which is passed to `propagate_types()`.
4988 The `cond_statement` cannot fit into a `binode` so a new `exec` is
4989 defined. As there are two scopes which cover multiple parts - one for
4990 the whole statement and one for "while" and "do" - and as we will use
4991 the 'struct exec' to track scopes, we actually need two new types of
4992 exec. One is a `binode` for the looping part, the rest is the
4993 `cond_statement`. The `cond_statement` will use an auxilliary `struct
4994 casepart` to track a list of case parts.
5005 struct exec *action;
5006 struct casepart *next;
5008 struct cond_statement {
5010 struct exec *forpart, *condpart, *thenpart, *elsepart;
5011 struct binode *looppart;
5012 struct casepart *casepart;
5015 ###### ast functions
5017 static void free_casepart(struct casepart *cp)
5021 free_exec(cp->value);
5022 free_exec(cp->action);
5029 static void free_cond_statement(struct cond_statement *s)
5033 free_exec(s->forpart);
5034 free_exec(s->condpart);
5035 free_exec(s->looppart);
5036 free_exec(s->thenpart);
5037 free_exec(s->elsepart);
5038 free_casepart(s->casepart);
5042 ###### free exec cases
5043 case Xcond_statement: free_cond_statement(cast(cond_statement, e)); break;
5045 ###### ComplexStatement Grammar
5046 | CondStatement ${ $0 = $<1; }$
5048 ###### declare terminals
5049 $TERM for then while do
5056 // A CondStatement must end with EOL, as does CondSuffix and
5058 // ForPart, ThenPart, SwitchPart, CasePart are non-empty and
5059 // may or may not end with EOL
5060 // WhilePart and IfPart include an appropriate Suffix
5062 // ForPart, SwitchPart, and IfPart open scopes, o we have to close
5063 // them. WhilePart opens and closes its own scope.
5064 CondStatement -> ForPart OptNL ThenPart OptNL WhilePart CondSuffix ${
5067 $0->thenpart = $<TP;
5068 $0->looppart = $<WP;
5069 var_block_close(c, CloseSequential, $0);
5071 | ForPart OptNL WhilePart CondSuffix ${
5074 $0->looppart = $<WP;
5075 var_block_close(c, CloseSequential, $0);
5077 | WhilePart CondSuffix ${
5079 $0->looppart = $<WP;
5081 | SwitchPart OptNL CasePart CondSuffix ${
5083 $0->condpart = $<SP;
5084 $CP->next = $0->casepart;
5085 $0->casepart = $<CP;
5086 var_block_close(c, CloseSequential, $0);
5088 | SwitchPart : IN OptNL CasePart CondSuffix OUT Newlines ${
5090 $0->condpart = $<SP;
5091 $CP->next = $0->casepart;
5092 $0->casepart = $<CP;
5093 var_block_close(c, CloseSequential, $0);
5095 | IfPart IfSuffix ${
5097 $0->condpart = $IP.condpart; $IP.condpart = NULL;
5098 $0->thenpart = $IP.thenpart; $IP.thenpart = NULL;
5099 // This is where we close an "if" statement
5100 var_block_close(c, CloseSequential, $0);
5103 CondSuffix -> IfSuffix ${
5106 | Newlines CasePart CondSuffix ${
5108 $CP->next = $0->casepart;
5109 $0->casepart = $<CP;
5111 | CasePart CondSuffix ${
5113 $CP->next = $0->casepart;
5114 $0->casepart = $<CP;
5117 IfSuffix -> Newlines ${ $0 = new(cond_statement); }$
5118 | Newlines ElsePart ${ $0 = $<EP; }$
5119 | ElsePart ${$0 = $<EP; }$
5121 ElsePart -> else OpenBlock Newlines ${
5122 $0 = new(cond_statement);
5123 $0->elsepart = $<OB;
5124 var_block_close(c, CloseElse, $0->elsepart);
5126 | else OpenScope CondStatement ${
5127 $0 = new(cond_statement);
5128 $0->elsepart = $<CS;
5129 var_block_close(c, CloseElse, $0->elsepart);
5133 CasePart -> case Expression OpenScope ColonBlock ${
5134 $0 = calloc(1,sizeof(struct casepart));
5137 var_block_close(c, CloseParallel, $0->action);
5141 // These scopes are closed in CondStatement
5142 ForPart -> for OpenBlock ${
5146 ThenPart -> then OpenBlock ${
5148 var_block_close(c, CloseSequential, $0);
5152 // This scope is closed in CondStatement
5153 WhilePart -> while UseBlock OptNL do OpenBlock ${
5158 var_block_close(c, CloseSequential, $0->right);
5159 var_block_close(c, CloseSequential, $0);
5161 | while OpenScope Expression OpenScope ColonBlock ${
5166 var_block_close(c, CloseSequential, $0->right);
5167 var_block_close(c, CloseSequential, $0);
5171 IfPart -> if UseBlock OptNL then OpenBlock ${
5174 var_block_close(c, CloseParallel, $0.thenpart);
5176 | if OpenScope Expression OpenScope ColonBlock ${
5179 var_block_close(c, CloseParallel, $0.thenpart);
5181 | if OpenScope Expression OpenScope OptNL then Block ${
5184 var_block_close(c, CloseParallel, $0.thenpart);
5188 // This scope is closed in CondStatement
5189 SwitchPart -> switch OpenScope Expression ${
5192 | switch UseBlock ${
5196 ###### print binode cases
5198 if (b->left && b->left->type == Xbinode &&
5199 cast(binode, b->left)->op == Block) {
5201 do_indent(indent, "while {\n");
5203 do_indent(indent, "while\n");
5204 print_exec(b->left, indent+1, bracket);
5206 do_indent(indent, "} do {\n");
5208 do_indent(indent, "do\n");
5209 print_exec(b->right, indent+1, bracket);
5211 do_indent(indent, "}\n");
5213 do_indent(indent, "while ");
5214 print_exec(b->left, 0, bracket);
5219 print_exec(b->right, indent+1, bracket);
5221 do_indent(indent, "}\n");
5225 ###### print exec cases
5227 case Xcond_statement:
5229 struct cond_statement *cs = cast(cond_statement, e);
5230 struct casepart *cp;
5232 do_indent(indent, "for");
5233 if (bracket) printf(" {\n"); else printf("\n");
5234 print_exec(cs->forpart, indent+1, bracket);
5237 do_indent(indent, "} then {\n");
5239 do_indent(indent, "then\n");
5240 print_exec(cs->thenpart, indent+1, bracket);
5242 if (bracket) do_indent(indent, "}\n");
5245 print_exec(cs->looppart, indent, bracket);
5249 do_indent(indent, "switch");
5251 do_indent(indent, "if");
5252 if (cs->condpart && cs->condpart->type == Xbinode &&
5253 cast(binode, cs->condpart)->op == Block) {
5258 print_exec(cs->condpart, indent+1, bracket);
5260 do_indent(indent, "}\n");
5262 do_indent(indent, "then\n");
5263 print_exec(cs->thenpart, indent+1, bracket);
5267 print_exec(cs->condpart, 0, bracket);
5273 print_exec(cs->thenpart, indent+1, bracket);
5275 do_indent(indent, "}\n");
5280 for (cp = cs->casepart; cp; cp = cp->next) {
5281 do_indent(indent, "case ");
5282 print_exec(cp->value, -1, 0);
5287 print_exec(cp->action, indent+1, bracket);
5289 do_indent(indent, "}\n");
5292 do_indent(indent, "else");
5297 print_exec(cs->elsepart, indent+1, bracket);
5299 do_indent(indent, "}\n");
5304 ###### propagate binode cases
5306 propagate_types(b->right, c, perr_local, Tnone, 0);
5307 return propagate_types(b->left, c, perr, type, rules);
5309 ###### propagate exec cases
5310 case Xcond_statement:
5312 // forpart and looppart->right must return Tnone
5313 // thenpart must return Tnone if there is a loopart,
5314 // otherwise it is like elsepart.
5316 // be bool if there is no casepart
5317 // match casepart->values if there is a switchpart
5318 // either be bool or match casepart->value if there
5320 // elsepart and casepart->action must match the return type
5321 // expected of this statement.
5322 struct cond_statement *cs = cast(cond_statement, prog);
5323 struct casepart *cp;
5325 t = propagate_types(cs->forpart, c, perr, Tnone, 0);
5328 t = propagate_types(cs->thenpart, c, perr, Tnone, 0);
5330 if (cs->casepart == NULL) {
5331 propagate_types(cs->condpart, c, perr, Tbool, 0);
5332 propagate_types(cs->looppart, c, perr, Tbool, 0);
5334 /* Condpart must match case values, with bool permitted */
5336 for (cp = cs->casepart;
5337 cp && !t; cp = cp->next)
5338 t = propagate_types(cp->value, c, perr, NULL, 0);
5339 if (!t && cs->condpart)
5340 t = propagate_types(cs->condpart, c, perr, NULL, Rboolok); // NOTEST
5341 if (!t && cs->looppart)
5342 t = propagate_types(cs->looppart, c, perr, NULL, Rboolok); // NOTEST
5343 // Now we have a type (I hope) push it down
5345 for (cp = cs->casepart; cp; cp = cp->next)
5346 propagate_types(cp->value, c, perr, t, 0);
5347 propagate_types(cs->condpart, c, perr, t, Rboolok);
5348 propagate_types(cs->looppart, c, perr, t, Rboolok);
5351 // (if)then, else, and case parts must return expected type.
5352 if (!cs->looppart && !type)
5353 type = propagate_types(cs->thenpart, c, perr, NULL, rules);
5355 type = propagate_types(cs->elsepart, c, perr, NULL, rules);
5356 for (cp = cs->casepart;
5358 cp = cp->next) // NOTEST
5359 type = propagate_types(cp->action, c, perr, NULL, rules); // NOTEST
5362 propagate_types(cs->thenpart, c, perr, type, rules);
5363 propagate_types(cs->elsepart, c, perr, type, rules);
5364 for (cp = cs->casepart; cp ; cp = cp->next)
5365 propagate_types(cp->action, c, perr, type, rules);
5371 ###### interp binode cases
5373 // This just performs one iterration of the loop
5374 rv = interp_exec(c, b->left, &rvtype);
5375 if (rvtype == Tnone ||
5376 (rvtype == Tbool && rv.bool != 0))
5377 // rvtype is Tnone or Tbool, doesn't need to be freed
5378 interp_exec(c, b->right, NULL);
5381 ###### interp exec cases
5382 case Xcond_statement:
5384 struct value v, cnd;
5385 struct type *vtype, *cndtype;
5386 struct casepart *cp;
5387 struct cond_statement *cs = cast(cond_statement, e);
5390 interp_exec(c, cs->forpart, NULL);
5392 while ((cnd = interp_exec(c, cs->looppart, &cndtype)),
5393 cndtype == Tnone || (cndtype == Tbool && cnd.bool != 0))
5394 interp_exec(c, cs->thenpart, NULL);
5396 cnd = interp_exec(c, cs->condpart, &cndtype);
5397 if ((cndtype == Tnone ||
5398 (cndtype == Tbool && cnd.bool != 0))) {
5399 // cnd is Tnone or Tbool, doesn't need to be freed
5400 rv = interp_exec(c, cs->thenpart, &rvtype);
5401 // skip else (and cases)
5405 for (cp = cs->casepart; cp; cp = cp->next) {
5406 v = interp_exec(c, cp->value, &vtype);
5407 if (value_cmp(cndtype, vtype, &v, &cnd) == 0) {
5408 free_value(vtype, &v);
5409 free_value(cndtype, &cnd);
5410 rv = interp_exec(c, cp->action, &rvtype);
5413 free_value(vtype, &v);
5415 free_value(cndtype, &cnd);
5417 rv = interp_exec(c, cs->elsepart, &rvtype);
5424 ### Top level structure
5426 All the language elements so far can be used in various places. Now
5427 it is time to clarify what those places are.
5429 At the top level of a file there will be a number of declarations.
5430 Many of the things that can be declared haven't been described yet,
5431 such as functions, procedures, imports, and probably more.
5432 For now there are two sorts of things that can appear at the top
5433 level. They are predefined constants, `struct` types, and the `main`
5434 function. While the syntax will allow the `main` function to appear
5435 multiple times, that will trigger an error if it is actually attempted.
5437 The various declarations do not return anything. They store the
5438 various declarations in the parse context.
5440 ###### Parser: grammar
5443 Ocean -> OptNL DeclarationList
5445 ## declare terminals
5453 DeclarationList -> Declaration
5454 | DeclarationList Declaration
5456 Declaration -> ERROR Newlines ${
5457 tok_err(c, // NOTEST
5458 "error: unhandled parse error", &$1);
5464 ## top level grammar
5468 ### The `const` section
5470 As well as being defined in with the code that uses them, constants can
5471 be declared at the top level. These have full-file scope, so they are
5472 always `InScope`, even before(!) they have been declared. The value of
5473 a top level constant can be given as an expression, and this is
5474 evaluated after parsing and before execution.
5476 A function call can be used to evaluate a constant, but it will not have
5477 access to any program state, once such statement becomes meaningful.
5478 e.g. arguments and filesystem will not be visible.
5480 Constants are defined in a section that starts with the reserved word
5481 `const` and then has a block with a list of assignment statements.
5482 For syntactic consistency, these must use the double-colon syntax to
5483 make it clear that they are constants. Type can also be given: if
5484 not, the type will be determined during analysis, as with other
5487 ###### parse context
5488 struct binode *constlist;
5490 ###### top level grammar
5494 DeclareConstant -> const { IN OptNL ConstList OUT OptNL } Newlines
5495 | const { SimpleConstList } Newlines
5496 | const IN OptNL ConstList OUT Newlines
5497 | const SimpleConstList Newlines
5499 ConstList -> ConstList SimpleConstLine
5502 SimpleConstList -> SimpleConstList ; Const
5506 SimpleConstLine -> SimpleConstList Newlines
5507 | ERROR Newlines ${ tok_err(c, "Syntax error in constant", &$1); }$
5510 CType -> Type ${ $0 = $<1; }$
5514 Const -> IDENTIFIER :: CType = Expression ${ {
5516 struct binode *bl, *bv;
5517 struct var *var = new_pos(var, $ID);
5519 v = var_decl(c, $ID.txt);
5521 v->where_decl = var;
5527 v = var_ref(c, $1.txt);
5528 if (v->type == Tnone) {
5529 v->where_decl = var;
5535 tok_err(c, "error: name already declared", &$1);
5536 type_err(c, "info: this is where '%v' was first declared",
5537 v->where_decl, NULL, 0, NULL);
5549 bl->left = c->constlist;
5554 ###### core functions
5555 static void resolve_consts(struct parse_context *c)
5559 enum { none, some, cannot } progress = none;
5561 c->constlist = reorder_bilist(c->constlist);
5564 for (b = cast(binode, c->constlist); b;
5565 b = cast(binode, b->right)) {
5567 struct binode *vb = cast(binode, b->left);
5568 struct var *v = cast(var, vb->left);
5569 if (v->var->frame_pos >= 0)
5573 propagate_types(vb->right, c, &perr,
5575 } while (perr & Eretry);
5577 c->parse_error += 1;
5578 else if (!(perr & Eruntime)) {
5580 struct value res = interp_exec(
5581 c, vb->right, &v->var->type);
5582 global_alloc(c, v->var->type, v->var, &res);
5584 if (progress == cannot)
5585 type_err(c, "error: const %v cannot be resolved.",
5595 progress = cannot; break;
5597 progress = none; break;
5602 ###### print const decls
5607 for (b = cast(binode, context.constlist); b;
5608 b = cast(binode, b->right)) {
5609 struct binode *vb = cast(binode, b->left);
5610 struct var *vr = cast(var, vb->left);
5611 struct variable *v = vr->var;
5617 printf(" %.*s :: ", v->name->name.len, v->name->name.txt);
5618 type_print(v->type, stdout);
5620 print_exec(vb->right, -1, 0);
5625 ###### free const decls
5626 free_binode(context.constlist);
5628 ### Function declarations
5630 The code in an Ocean program is all stored in function declarations.
5631 One of the functions must be named `main` and it must accept an array of
5632 strings as a parameter - the command line arguments.
5634 As this is the top level, several things are handled a bit differently.
5635 The function is not interpreted by `interp_exec` as that isn't passed
5636 the argument list which the program requires. Similarly type analysis
5637 is a bit more interesting at this level.
5639 ###### ast functions
5641 static struct type *handle_results(struct parse_context *c,
5642 struct binode *results)
5644 /* Create a 'struct' type from the results list, which
5645 * is a list for 'struct var'
5647 struct type *t = add_anon_type(c, &structure_prototype,
5652 for (b = results; b; b = cast(binode, b->right))
5654 t->structure.nfields = cnt;
5655 t->structure.fields = calloc(cnt, sizeof(struct field));
5657 for (b = results; b; b = cast(binode, b->right)) {
5658 struct var *v = cast(var, b->left);
5659 struct field *f = &t->structure.fields[cnt++];
5660 int a = v->var->type->align;
5661 f->name = v->var->name->name;
5662 f->type = v->var->type;
5664 f->offset = t->size;
5665 v->var->frame_pos = f->offset;
5666 t->size += ((f->type->size - 1) | (a-1)) + 1;
5669 variable_unlink_exec(v->var);
5671 free_binode(results);
5675 static struct variable *declare_function(struct parse_context *c,
5676 struct variable *name,
5677 struct binode *args,
5679 struct binode *results,
5683 struct value fn = {.function = code};
5685 var_block_close(c, CloseFunction, code);
5686 t = add_anon_type(c, &function_prototype,
5687 "func %.*s", name->name->name.len,
5688 name->name->name.txt);
5690 t->function.params = reorder_bilist(args);
5692 ret = handle_results(c, reorder_bilist(results));
5693 t->function.inline_result = 1;
5694 t->function.local_size = ret->size;
5696 t->function.return_type = ret;
5697 global_alloc(c, t, name, &fn);
5698 name->type->function.scope = c->out_scope;
5703 var_block_close(c, CloseFunction, NULL);
5705 c->out_scope = NULL;
5709 ###### declare terminals
5712 ###### top level grammar
5715 DeclareFunction -> func FuncName ( OpenScope ArgsLine ) Block Newlines ${
5716 $0 = declare_function(c, $<FN, $<Ar, Tnone, NULL, $<Bl);
5718 | func FuncName IN OpenScope Args OUT OptNL do Block Newlines ${
5719 $0 = declare_function(c, $<FN, $<Ar, Tnone, NULL, $<Bl);
5721 | func FuncName NEWLINE OpenScope OptNL do Block Newlines ${
5722 $0 = declare_function(c, $<FN, NULL, Tnone, NULL, $<Bl);
5724 | func FuncName ( OpenScope ArgsLine ) : Type Block Newlines ${
5725 $0 = declare_function(c, $<FN, $<Ar, $<Ty, NULL, $<Bl);
5727 | func FuncName ( OpenScope ArgsLine ) : ( ArgsLine ) Block Newlines ${
5728 $0 = declare_function(c, $<FN, $<AL, NULL, $<AL2, $<Bl);
5730 | func FuncName IN OpenScope Args OUT OptNL return Type Newlines do Block Newlines ${
5731 $0 = declare_function(c, $<FN, $<Ar, $<Ty, NULL, $<Bl);
5733 | func FuncName NEWLINE OpenScope return Type Newlines do Block Newlines ${
5734 $0 = declare_function(c, $<FN, NULL, $<Ty, NULL, $<Bl);
5736 | func FuncName IN OpenScope Args OUT OptNL return IN Args OUT OptNL do Block Newlines ${
5737 $0 = declare_function(c, $<FN, $<Ar, NULL, $<Ar2, $<Bl);
5739 | func FuncName NEWLINE OpenScope return IN Args OUT OptNL do Block Newlines ${
5740 $0 = declare_function(c, $<FN, NULL, NULL, $<Ar, $<Bl);
5743 ###### print func decls
5748 while (target != 0) {
5750 for (v = context.in_scope; v; v=v->in_scope)
5751 if (v->depth == 0 && v->type && v->type->check_args) {
5760 struct value *val = var_value(&context, v);
5761 printf("func %.*s", v->name->name.len, v->name->name.txt);
5762 v->type->print_type_decl(v->type, stdout);
5765 print_exec(val->function, 1, brackets);
5768 print_value(v->type, val, stdout);
5770 printf("/* frame size %d */\n", v->type->function.local_size);
5776 ###### core functions
5778 static int analyse_funcs(struct parse_context *c)
5782 for (v = c->in_scope; v; v = v->in_scope) {
5786 if (v->depth != 0 || !v->type || !v->type->check_args)
5788 ret = v->type->function.inline_result ?
5789 Tnone : v->type->function.return_type;
5790 val = var_value(c, v);
5793 propagate_types(val->function, c, &perr, ret, 0);
5794 } while (!(perr & Efail) && (perr & Eretry));
5795 if (!(perr & Efail))
5796 /* Make sure everything is still consistent */
5797 propagate_types(val->function, c, &perr, ret, 0);
5800 if (!v->type->function.inline_result &&
5801 !v->type->function.return_type->dup) {
5802 type_err(c, "error: function cannot return value of type %1",
5803 v->where_decl, v->type->function.return_type, 0, NULL);
5806 scope_finalize(c, v->type);
5811 static int analyse_main(struct type *type, struct parse_context *c)
5813 struct binode *bp = type->function.params;
5817 struct type *argv_type;
5819 argv_type = add_anon_type(c, &array_prototype, "argv");
5820 argv_type->array.member = Tstr;
5821 argv_type->array.unspec = 1;
5823 for (b = bp; b; b = cast(binode, b->right)) {
5827 propagate_types(b->left, c, &perr, argv_type, 0);
5829 default: /* invalid */ // NOTEST
5830 propagate_types(b->left, c, &perr, Tnone, 0); // NOTEST
5833 c->parse_error += 1;
5836 return !c->parse_error;
5839 static void interp_main(struct parse_context *c, int argc, char **argv)
5841 struct value *progp = NULL;
5842 struct text main_name = { "main", 4 };
5843 struct variable *mainv;
5849 mainv = var_ref(c, main_name);
5851 progp = var_value(c, mainv);
5852 if (!progp || !progp->function) {
5853 fprintf(stderr, "oceani: no main function found.\n");
5854 c->parse_error += 1;
5857 if (!analyse_main(mainv->type, c)) {
5858 fprintf(stderr, "oceani: main has wrong type.\n");
5859 c->parse_error += 1;
5862 al = mainv->type->function.params;
5864 c->local_size = mainv->type->function.local_size;
5865 c->local = calloc(1, c->local_size);
5867 struct var *v = cast(var, al->left);
5868 struct value *vl = var_value(c, v->var);
5876 t->array.size = argc;
5877 t->prepare_type(c, t, 0);
5878 array_init(v->var->type, vl);
5879 for (i = 0; i < argc; i++) {
5880 struct value *vl2 = vl->array + i * v->var->type->array.member->size;
5882 arg.str.txt = argv[i];
5883 arg.str.len = strlen(argv[i]);
5884 free_value(Tstr, vl2);
5885 dup_value(Tstr, &arg, vl2);
5889 al = cast(binode, al->right);
5891 v = interp_exec(c, progp->function, &vtype);
5892 free_value(vtype, &v);
5897 ###### ast functions
5898 void free_variable(struct variable *v)
5902 ## And now to test it out.
5904 Having a language requires having a "hello world" program. I'll
5905 provide a little more than that: a program that prints "Hello world"
5906 finds the GCD of two numbers, prints the first few elements of
5907 Fibonacci, performs a binary search for a number, and a few other
5908 things which will likely grow as the languages grows.
5910 ###### File: oceani.mk
5913 @echo "===== DEMO ====="
5914 ./oceani --section "demo: hello" oceani.mdc 55 33
5920 four ::= 2 + 2 ; five ::= 10/2
5921 const pie ::= "I like Pie";
5922 cake ::= "The cake is"
5930 func main(argv:[]string)
5931 print "Hello World, what lovely oceans you have!"
5932 print "Are there", five, "?"
5933 print pi, pie, "but", cake
5935 A := $argv[1]; B := $argv[2]
5937 /* When a variable is defined in both branches of an 'if',
5938 * and used afterwards, the variables are merged.
5944 print "Is", A, "bigger than", B,"? ", bigger
5945 /* If a variable is not used after the 'if', no
5946 * merge happens, so types can be different
5949 double:string = "yes"
5950 print A, "is more than twice", B, "?", double
5953 print "double", B, "is", double
5964 print "GCD of", A, "and", B,"is", a
5966 print a, "is not positive, cannot calculate GCD"
5968 print b, "is not positive, cannot calculate GCD"
5973 print "Fibonacci:", f1,f2,
5974 then togo = togo - 1
5982 /* Binary search... */
5987 mid := (lo + hi) / 2
6000 print "Yay, I found", target
6002 print "Closest I found was", lo
6007 // "middle square" PRNG. Not particularly good, but one my
6008 // Dad taught me - the first one I ever heard of.
6009 for i:=1; then i = i + 1; while i < size:
6010 n := list[i-1] * list[i-1]
6011 list[i] = (n / 100) % 10 000
6013 print "Before sort:",
6014 for i:=0; then i = i + 1; while i < size:
6018 for i := 1; then i=i+1; while i < size:
6019 for j:=i-1; then j=j-1; while j >= 0:
6020 if list[j] > list[j+1]:
6024 print " After sort:",
6025 for i:=0; then i = i + 1; while i < size:
6029 if 1 == 2 then print "yes"; else print "no"
6033 bob.alive = (bob.name == "Hello")
6034 print "bob", "is" if bob.alive else "isn't", "alive"