1 # Ocean Interpreter - Jamison Creek version
3 Ocean is intended to be a compiled language, so this interpreter is
4 not targeted at being the final product. It is, rather, an intermediate
5 stage and fills that role in two distinct ways.
7 Firstly, it exists as a platform to experiment with the early language
8 design. An interpreter is easy to write and easy to get working, so
9 the barrier for entry is lower if I aim to start with an interpreter.
11 Secondly, the plan for the Ocean compiler is to write it in the
12 [Ocean language](http://ocean-lang.org). To achieve this we naturally
13 need some sort of boot-strap process and this interpreter - written in
14 portable C - will fill that role. It will be used to bootstrap the
17 Two features that are not needed to fill either of these roles are
18 performance and completeness. The interpreter only needs to be fast
19 enough to run small test programs and occasionally to run the compiler
20 on itself. It only needs to be complete enough to test aspects of the
21 design which are developed before the compiler is working, and to run
22 the compiler on itself. Any features not used by the compiler when
23 compiling itself are superfluous. They may be included anyway, but
26 Nonetheless, the interpreter should end up being reasonably complete,
27 and any performance bottlenecks which appear and are easily fixed, will
32 This third version of the interpreter exists to test out some initial
33 ideas relating to types. Particularly it adds arrays (indexed from
34 zero) and simple structures. Basic control flow and variable scoping
35 are already fairly well established, as are basic numerical and
38 Some operators that have only recently been added, and so have not
39 generated all that much experience yet are "and then" and "or else" as
40 short-circuit Boolean operators, and the "if ... else" trinary
41 operator which can select between two expressions based on a third
42 (which appears syntactically in the middle).
44 The "func" clause currently only allows a "main" function to be
45 declared. That will be extended when proper function support is added.
47 An element that is present purely to make a usable language, and
48 without any expectation that they will remain, is the "print" statement
49 which performs simple output.
51 The current scalar types are "number", "Boolean", and "string".
52 Boolean will likely stay in its current form, the other two might, but
53 could just as easily be changed.
57 Versions of the interpreter which obviously do not support a complete
58 language will be named after creeks and streams. This one is Jamison
61 Once we have something reasonably resembling a complete language, the
62 names of rivers will be used.
63 Early versions of the compiler will be named after seas. Major
64 releases of the compiler will be named after oceans. Hopefully I will
65 be finished once I get to the Pacific Ocean release.
69 As well as parsing and executing a program, the interpreter can print
70 out the program from the parsed internal structure. This is useful
71 for validating the parsing.
72 So the main requirements of the interpreter are:
74 - Parse the program, possibly with tracing,
75 - Analyse the parsed program to ensure consistency,
77 - Execute the "main" function in the program, if no parsing or
78 consistency errors were found.
80 This is all performed by a single C program extracted with
83 There will be two formats for printing the program: a default and one
84 that uses bracketing. So a `--bracket` command line option is needed
85 for that. Normally the first code section found is used, however an
86 alternate section can be requested so that a file (such as this one)
87 can contain multiple programs. This is effected with the `--section`
90 This code must be compiled with `-fplan9-extensions` so that anonymous
91 structures can be used.
93 ###### File: oceani.mk
95 myCFLAGS := -Wall -g -fplan9-extensions
96 CFLAGS := $(filter-out $(myCFLAGS),$(CFLAGS)) $(myCFLAGS)
97 myLDLIBS:= libparser.o libscanner.o libmdcode.o -licuuc
98 LDLIBS := $(filter-out $(myLDLIBS),$(LDLIBS)) $(myLDLIBS)
100 all :: $(LDLIBS) oceani
101 oceani.c oceani.h : oceani.mdc parsergen
102 ./parsergen -o oceani --LALR --tag Parser oceani.mdc
103 oceani.mk: oceani.mdc md2c
106 oceani: oceani.o $(LDLIBS)
107 $(CC) $(CFLAGS) -o oceani oceani.o $(LDLIBS)
109 ###### Parser: header
111 struct parse_context;
113 struct parse_context {
114 struct token_config config;
122 #define container_of(ptr, type, member) ({ \
123 const typeof( ((type *)0)->member ) *__mptr = (ptr); \
124 (type *)( (char *)__mptr - offsetof(type,member) );})
126 #define config2context(_conf) container_of(_conf, struct parse_context, \
129 ###### Parser: reduce
130 struct parse_context *c = config2context(config);
138 #include <sys/mman.h>
157 static char Usage[] =
158 "Usage: oceani --trace --print --noexec --brackets --section=SectionName prog.ocn\n";
159 static const struct option long_options[] = {
160 {"trace", 0, NULL, 't'},
161 {"print", 0, NULL, 'p'},
162 {"noexec", 0, NULL, 'n'},
163 {"brackets", 0, NULL, 'b'},
164 {"section", 1, NULL, 's'},
167 const char *options = "tpnbs";
169 static void pr_err(char *msg) // NOTEST
171 fprintf(stderr, "%s\n", msg); // NOTEST
174 int main(int argc, char *argv[])
179 struct section *s = NULL, *ss;
180 char *section = NULL;
181 struct parse_context context = {
183 .ignored = (1 << TK_mark),
184 .number_chars = ".,_+- ",
189 int doprint=0, dotrace=0, doexec=1, brackets=0;
191 while ((opt = getopt_long(argc, argv, options, long_options, NULL))
194 case 't': dotrace=1; break;
195 case 'p': doprint=1; break;
196 case 'n': doexec=0; break;
197 case 'b': brackets=1; break;
198 case 's': section = optarg; break;
199 default: fprintf(stderr, Usage);
203 if (optind >= argc) {
204 fprintf(stderr, "oceani: no input file given\n");
207 fd = open(argv[optind], O_RDONLY);
209 fprintf(stderr, "oceani: cannot open %s\n", argv[optind]);
212 context.file_name = argv[optind];
213 len = lseek(fd, 0, 2);
214 file = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
215 s = code_extract(file, file+len, pr_err);
217 fprintf(stderr, "oceani: could not find any code in %s\n",
222 ## context initialization
225 for (ss = s; ss; ss = ss->next) {
226 struct text sec = ss->section;
227 if (sec.len == strlen(section) &&
228 strncmp(sec.txt, section, sec.len) == 0)
232 fprintf(stderr, "oceani: cannot find section %s\n",
239 fprintf(stderr, "oceani: no code found in requested section\n"); // NOTEST
240 goto cleanup; // NOTEST
243 parse_oceani(ss->code, &context.config, dotrace ? stderr : NULL);
245 resolve_consts(&context);
246 prepare_types(&context);
247 if (!context.parse_error && !analyse_funcs(&context)) {
248 fprintf(stderr, "oceani: type error in program - not running.\n");
249 context.parse_error += 1;
257 if (doexec && !context.parse_error)
258 interp_main(&context, argc - optind, argv + optind);
261 struct section *t = s->next;
266 // FIXME parser should pop scope even on error
267 while (context.scope_depth > 0)
271 ## free context types
272 ## free context storage
273 exit(context.parse_error ? 1 : 0);
278 The four requirements of parse, analyse, print, interpret apply to
279 each language element individually so that is how most of the code
282 Three of the four are fairly self explanatory. The one that requires
283 a little explanation is the analysis step.
285 The current language design does not require the types of variables to
286 be declared, but they must still have a single type. Different
287 operations impose different requirements on the variables, for example
288 addition requires both arguments to be numeric, and assignment
289 requires the variable on the left to have the same type as the
290 expression on the right.
292 Analysis involves propagating these type requirements around and
293 consequently setting the type of each variable. If any requirements
294 are violated (e.g. a string is compared with a number) or if a
295 variable needs to have two different types, then an error is raised
296 and the program will not run.
298 If the same variable is declared in both branchs of an 'if/else', or
299 in all cases of a 'switch' then the multiple instances may be merged
300 into just one variable if the variable is referenced after the
301 conditional statement. When this happens, the types must naturally be
302 consistent across all the branches. When the variable is not used
303 outside the if, the variables in the different branches are distinct
304 and can be of different types.
306 Undeclared names may only appear in "use" statements and "case" expressions.
307 These names are given a type of "label" and a unique value.
308 This allows them to fill the role of a name in an enumerated type, which
309 is useful for testing the `switch` statement.
311 As we will see, the condition part of a `while` statement can return
312 either a Boolean or some other type. This requires that the expected
313 type that gets passed around comprises a type and a flag to indicate
314 that `Tbool` is also permitted.
316 As there are, as yet, no distinct types that are compatible, there
317 isn't much subtlety in the analysis. When we have distinct number
318 types, this will become more interesting.
322 When analysis discovers an inconsistency it needs to report an error;
323 just refusing to run the code ensures that the error doesn't cascade,
324 but by itself it isn't very useful. A clear understanding of the sort
325 of error message that are useful will help guide the process of
328 At a simplistic level, the only sort of error that type analysis can
329 report is that the type of some construct doesn't match a contextual
330 requirement. For example, in `4 + "hello"` the addition provides a
331 contextual requirement for numbers, but `"hello"` is not a number. In
332 this particular example no further information is needed as the types
333 are obvious from local information. When a variable is involved that
334 isn't the case. It may be helpful to explain why the variable has a
335 particular type, by indicating the location where the type was set,
336 whether by declaration or usage.
338 Using a recursive-descent analysis we can easily detect a problem at
339 multiple locations. In "`hello:= "there"; 4 + hello`" the addition
340 will detect that one argument is not a number and the usage of `hello`
341 will detect that a number was wanted, but not provided. In this
342 (early) version of the language, we will generate error reports at
343 multiple locations, so the use of `hello` will report an error and
344 explain were the value was set, and the addition will report an error
345 and say why numbers are needed. To be able to report locations for
346 errors, each language element will need to record a file location
347 (line and column) and each variable will need to record the language
348 element where its type was set. For now we will assume that each line
349 of an error message indicates one location in the file, and up to 2
350 types. So we provide a `printf`-like function which takes a format, a
351 location (a `struct exec` which has not yet been introduced), and 2
352 types. "`%1`" reports the first type, "`%2`" reports the second. We
353 will need a function to print the location, once we know how that is
354 stored. e As will be explained later, there are sometimes extra rules for
355 type matching and they might affect error messages, we need to pass those
358 As well as type errors, we sometimes need to report problems with
359 tokens, which might be unexpected or might name a type that has not
360 been defined. For these we have `tok_err()` which reports an error
361 with a given token. Each of the error functions sets the flag in the
362 context so indicate that parsing failed.
366 static void fput_loc(struct exec *loc, FILE *f);
367 static void type_err(struct parse_context *c,
368 char *fmt, struct exec *loc,
369 struct type *t1, int rules, struct type *t2);
370 static void tok_err(struct parse_context *c, char *fmt, struct token *t);
372 ###### core functions
374 static void type_err(struct parse_context *c,
375 char *fmt, struct exec *loc,
376 struct type *t1, int rules, struct type *t2)
378 fprintf(stderr, "%s:", c->file_name);
379 fput_loc(loc, stderr);
380 for (; *fmt ; fmt++) {
387 case '%': fputc(*fmt, stderr); break; // NOTEST
388 default: fputc('?', stderr); break; // NOTEST
390 type_print(t1, stderr);
393 type_print(t2, stderr);
402 static void tok_err(struct parse_context *c, char *fmt, struct token *t)
404 fprintf(stderr, "%s:%d:%d: %s: %.*s\n", c->file_name, t->line, t->col, fmt,
405 t->txt.len, t->txt.txt);
409 ## Entities: declared and predeclared.
411 There are various "things" that the language and/or the interpreter
412 needs to know about to parse and execute a program. These include
413 types, variables, values, and executable code. These are all lumped
414 together under the term "entities" (calling them "objects" would be
415 confusing) and introduced here. The following section will present the
416 different specific code elements which comprise or manipulate these
421 Executables can be lots of different things. In many cases an
422 executable is just an operation combined with one or two other
423 executables. This allows for expressions and lists etc. Other times an
424 executable is something quite specific like a constant or variable name.
425 So we define a `struct exec` to be a general executable with a type, and
426 a `struct binode` which is a subclass of `exec`, forms a node in a
427 binary tree, and holds an operation. There will be other subclasses,
428 and to access these we need to be able to `cast` the `exec` into the
429 various other types. The first field in any `struct exec` is the type
430 from the `exec_types` enum.
433 #define cast(structname, pointer) ({ \
434 const typeof( ((struct structname *)0)->type) *__mptr = &(pointer)->type; \
435 if (__mptr && *__mptr != X##structname) abort(); \
436 (struct structname *)( (char *)__mptr);})
438 #define new(structname) ({ \
439 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
440 __ptr->type = X##structname; \
441 __ptr->line = -1; __ptr->column = -1; \
444 #define new_pos(structname, token) ({ \
445 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
446 __ptr->type = X##structname; \
447 __ptr->line = token.line; __ptr->column = token.col; \
456 enum exec_types type;
465 struct exec *left, *right;
470 static int __fput_loc(struct exec *loc, FILE *f)
474 if (loc->line >= 0) {
475 fprintf(f, "%d:%d: ", loc->line, loc->column);
478 if (loc->type == Xbinode)
479 return __fput_loc(cast(binode,loc)->left, f) ||
480 __fput_loc(cast(binode,loc)->right, f); // NOTEST
483 static void fput_loc(struct exec *loc, FILE *f)
485 if (!__fput_loc(loc, f))
486 fprintf(f, "??:??: "); // NOTEST
489 Each different type of `exec` node needs a number of functions defined,
490 a bit like methods. We must be able to free it, print it, analyse it
491 and execute it. Once we have specific `exec` types we will need to
492 parse them too. Let's take this a bit more slowly.
496 The parser generator requires a `free_foo` function for each struct
497 that stores attributes and they will often be `exec`s and subtypes
498 there-of. So we need `free_exec` which can handle all the subtypes,
499 and we need `free_binode`.
503 static void free_binode(struct binode *b)
512 ###### core functions
513 static void free_exec(struct exec *e)
524 static void free_exec(struct exec *e);
526 ###### free exec cases
527 case Xbinode: free_binode(cast(binode, e)); break;
531 Printing an `exec` requires that we know the current indent level for
532 printing line-oriented components. As will become clear later, we
533 also want to know what sort of bracketing to use.
537 static void do_indent(int i, char *str)
544 ###### core functions
545 static void print_binode(struct binode *b, int indent, int bracket)
549 ## print binode cases
553 static void print_exec(struct exec *e, int indent, int bracket)
559 print_binode(cast(binode, e), indent, bracket); break;
564 do_indent(indent, "/* FREE");
565 for (v = e->to_free; v; v = v->next_free) {
566 printf(" %.*s", v->name->name.len, v->name->name.txt);
567 printf("[%d,%d]", v->scope_start, v->scope_end);
568 if (v->frame_pos >= 0)
569 printf("(%d+%d)", v->frame_pos,
570 v->type ? v->type->size:0);
578 static void print_exec(struct exec *e, int indent, int bracket);
582 As discussed, analysis involves propagating type requirements around the
583 program and looking for errors.
585 So `propagate_types` is passed an expected type (being a `struct type`
586 pointer together with some `val_rules` flags) that the `exec` is
587 expected to return, and returns the type that it does return, either of
588 which can be `NULL` signifying "unknown". A `prop_err` flag set is
589 passed by reference. It has `Efail` set when an error is found, and
590 `Eretry` when the type for some element is set via propagation. If
591 any expression cannot be evaluated immediately, `Enoconst` is set.
592 If the expression can be copied, `Emaycopy` is set.
594 If it remains unchanged at `0`, then no more propagation is needed.
598 enum val_rules {Rnolabel = 1<<0, Rboolok = 1<<1, Rnoconstant = 1<<2};
599 enum prop_err {Efail = 1<<0, Eretry = 1<<1, Enoconst = 1<<2,
604 if (rules & Rnolabel)
605 fputs(" (labels not permitted)", stderr);
609 static struct type *propagate_types(struct exec *prog, struct parse_context *c, enum prop_err *perr,
610 struct type *type, int rules);
611 ###### core functions
613 static struct type *__propagate_types(struct exec *prog, struct parse_context *c, enum prop_err *perr,
614 struct type *type, int rules)
621 switch (prog->type) {
624 struct binode *b = cast(binode, prog);
626 ## propagate binode cases
630 ## propagate exec cases
635 static struct type *propagate_types(struct exec *prog, struct parse_context *c, enum prop_err *perr,
636 struct type *type, int rules)
638 int pre_err = c->parse_error;
639 struct type *ret = __propagate_types(prog, c, perr, type, rules);
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
795 struct token first_use;
798 void (*init)(struct type *type, struct value *val);
799 int (*prepare_type)(struct parse_context *c, struct type *type, int parse_time);
800 void (*print)(struct type *type, struct value *val, FILE *f);
801 void (*print_type)(struct type *type, FILE *f);
802 int (*cmp_order)(struct type *t1, struct type *t2,
803 struct value *v1, struct value *v2);
804 int (*cmp_eq)(struct type *t1, struct type *t2,
805 struct value *v1, struct value *v2);
806 void (*dup)(struct type *type, struct value *vold, struct value *vnew);
807 int (*test)(struct type *type, struct value *val);
808 void (*free)(struct type *type, struct value *val);
809 void (*free_type)(struct type *t);
810 long long (*to_int)(struct value *v);
811 double (*to_float)(struct value *v);
812 int (*to_mpq)(mpq_t *q, struct value *v);
821 struct type *typelist;
828 static struct type *find_type(struct parse_context *c, struct text s)
830 struct type *t = c->typelist;
832 while (t && (t->anon ||
833 text_cmp(t->name, s) != 0))
838 static struct type *_add_type(struct parse_context *c, struct text s,
839 struct type *proto, int anon)
843 n = calloc(1, sizeof(*n));
850 n->next = c->typelist;
855 static struct type *add_type(struct parse_context *c, struct text s,
858 return _add_type(c, s, proto, 0);
861 static struct type *add_anon_type(struct parse_context *c,
862 struct type *proto, char *name, ...)
868 vasprintf(&t.txt, name, ap);
870 t.len = strlen(t.txt);
871 return _add_type(c, t, proto, 1);
874 static struct type *find_anon_type(struct parse_context *c,
875 struct type *proto, char *name, ...)
877 struct type *t = c->typelist;
882 vasprintf(&nm.txt, name, ap);
884 nm.len = strlen(name);
886 while (t && (!t->anon ||
887 text_cmp(t->name, nm) != 0))
893 return _add_type(c, nm, proto, 1);
896 static void free_type(struct type *t)
898 /* The type is always a reference to something in the
899 * context, so we don't need to free anything.
903 static void free_value(struct type *type, struct value *v)
907 memset(v, 0x5a, type->size);
911 static void type_print(struct type *type, FILE *f)
914 fputs("*unknown*type*", f); // NOTEST
915 else if (type->name.len && !type->anon)
916 fprintf(f, "%.*s", type->name.len, type->name.txt);
917 else if (type->print_type)
918 type->print_type(type, f);
919 else if (type->name.len && type->anon)
920 fprintf(f, "\"%.*s\"", type->name.len, type->name.txt);
922 fputs("*invalid*type*", f); // NOTEST
925 static void val_init(struct type *type, struct value *val)
927 if (type && type->init)
928 type->init(type, val);
931 static void dup_value(struct type *type,
932 struct value *vold, struct value *vnew)
934 if (type && type->dup)
935 type->dup(type, vold, vnew);
938 static int value_cmp(struct type *tl, struct type *tr,
939 struct value *left, struct value *right)
941 if (tl && tl->cmp_order)
942 return tl->cmp_order(tl, tr, left, right);
943 if (tl && tl->cmp_eq)
944 return tl->cmp_eq(tl, tr, left, right);
948 static void print_value(struct type *type, struct value *v, FILE *f)
950 if (type && type->print)
951 type->print(type, v, f);
953 fprintf(f, "*Unknown*"); // NOTEST
956 static void prepare_types(struct parse_context *c)
960 enum { none, some, cannot } progress = none;
965 for (t = c->typelist; t; t = t->next) {
967 tok_err(c, "error: type used but not declared",
969 if (t->size == 0 && t->prepare_type) {
970 if (t->prepare_type(c, t, 1))
972 else if (progress == cannot)
973 tok_err(c, "error: type has recursive definition",
983 progress = cannot; break;
985 progress = none; break;
992 static void free_value(struct type *type, struct value *v);
993 static int type_compat(struct type *require, struct type *have, int rules);
994 static void type_print(struct type *type, FILE *f);
995 static void val_init(struct type *type, struct value *v);
996 static void dup_value(struct type *type,
997 struct value *vold, struct value *vnew);
998 static int value_cmp(struct type *tl, struct type *tr,
999 struct value *left, struct value *right);
1000 static void print_value(struct type *type, struct value *v, FILE *f);
1002 ###### free context types
1004 while (context.typelist) {
1005 struct type *t = context.typelist;
1007 context.typelist = t->next;
1015 Type can be specified for local variables, for fields in a structure,
1016 for formal parameters to functions, and possibly elsewhere. Different
1017 rules may apply in different contexts. As a minimum, a named type may
1018 always be used. Currently the type of a formal parameter can be
1019 different from types in other contexts, so we have a separate grammar
1025 Type -> IDENTIFIER ${
1026 $0 = find_type(c, $ID.txt);
1028 $0 = add_type(c, $ID.txt, NULL);
1029 $0->first_use = $ID;
1034 FormalType -> Type ${ $0 = $<1; }$
1035 ## formal type grammar
1039 Values of the base types can be numbers, which we represent as
1040 multi-precision fractions, strings, Booleans and labels. When
1041 analysing the program we also need to allow for places where no value
1042 is meaningful (type `Tnone`) and where we don't know what type to
1043 expect yet (type is `NULL`).
1045 Values are never shared, they are always copied when used, and freed
1046 when no longer needed.
1048 When propagating type information around the program, we need to
1049 determine if two types are compatible, where type `NULL` is compatible
1050 with anything. There are two special cases with type compatibility,
1051 both related to the Conditional Statement which will be described
1052 later. In some cases a Boolean can be accepted as well as some other
1053 primary type, and in others any type is acceptable except a label (`Vlabel`).
1054 A separate function encoding these cases will simplify some code later.
1056 ###### type functions
1058 int (*compat)(struct type *this, struct type *other);
1060 ###### ast functions
1062 static int type_compat(struct type *require, struct type *have, int rules)
1064 if ((rules & Rboolok) && have == Tbool)
1066 if ((rules & Rnolabel) && have == Tlabel)
1068 if (!require || !have)
1071 if (require->compat)
1072 return require->compat(require, have);
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);
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;
1141 vnew->bool = vold->bool;
1144 mpq_init(vnew->num);
1145 mpq_set(vnew->num, vold->num);
1148 vnew->str.len = vold->str.len;
1149 vnew->str.txt = malloc(vnew->str.len);
1150 memcpy(vnew->str.txt, vold->str.txt, vnew->str.len);
1155 static int _value_cmp(struct type *tl, struct type *tr,
1156 struct value *left, struct value *right)
1160 return tl - tr; // NOTEST
1161 switch (tl->vtype) {
1162 case Vlabel: cmp = left->label == right->label ? 0 : 1; break;
1163 case Vnum: cmp = mpq_cmp(left->num, right->num); break;
1164 case Vstr: cmp = text_cmp(left->str, right->str); break;
1165 case Vbool: cmp = left->bool - right->bool; break;
1166 case Vnone: cmp = 0; // NOTEST
1171 static void _print_value(struct type *type, struct value *v, FILE *f)
1173 switch (type->vtype) {
1174 case Vnone: // NOTEST
1175 fprintf(f, "*no-value*"); break; // NOTEST
1176 case Vlabel: // NOTEST
1177 fprintf(f, "*label-%p*", 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);
1268 $0 = new_val(Tbool, $1);
1272 $0 = new_val(Tbool, $1);
1277 $0 = new_val(Tnum, $1);
1278 if (number_parse($0->val.num, tail, $1.txt) == 0)
1279 mpq_init($0->val.num); // UNTESTED
1281 tok_err(c, "error: unsupported number suffix",
1286 $0 = new_val(Tstr, $1);
1287 string_parse(&$1, '\\', &$0->val.str, tail);
1289 tok_err(c, "error: unsupported string suffix",
1294 $0 = new_val(Tstr, $1);
1295 string_parse(&$1, '\\', &$0->val.str, tail);
1297 tok_err(c, "error: unsupported string suffix",
1301 ###### print exec cases
1304 struct val *v = cast(val, e);
1305 if (v->vtype == Tstr)
1307 // FIXME how to ensure numbers have same precision.
1308 print_value(v->vtype, &v->val, stdout);
1309 if (v->vtype == Tstr)
1314 ###### propagate exec cases
1317 struct val *val = cast(val, prog);
1318 if (!type_compat(type, val->vtype, rules))
1319 type_err(c, "error: expected %1%r found %2",
1320 prog, type, rules, val->vtype);
1324 ###### interp exec cases
1326 rvtype = cast(val, e)->vtype;
1327 dup_value(rvtype, &cast(val, e)->val, &rv);
1330 ###### ast functions
1331 static void free_val(struct val *v)
1334 free_value(v->vtype, &v->val);
1338 ###### free exec cases
1339 case Xval: free_val(cast(val, e)); break;
1341 ###### ast functions
1342 // Move all nodes from 'b' to 'rv', reversing their order.
1343 // In 'b' 'left' is a list, and 'right' is the last node.
1344 // In 'rv', left' is the first node and 'right' is a list.
1345 static struct binode *reorder_bilist(struct binode *b)
1347 struct binode *rv = NULL;
1350 struct exec *t = b->right;
1354 b = cast(binode, b->left);
1364 Variables are scoped named values. We store the names in a linked list
1365 of "bindings" sorted in lexical order, and use sequential search and
1372 struct binding *next; // in lexical order
1376 This linked list is stored in the parse context so that "reduce"
1377 functions can find or add variables, and so the analysis phase can
1378 ensure that every variable gets a type.
1380 ###### parse context
1382 struct binding *varlist; // In lexical order
1384 ###### ast functions
1386 static struct binding *find_binding(struct parse_context *c, struct text s)
1388 struct binding **l = &c->varlist;
1393 (cmp = text_cmp((*l)->name, s)) < 0)
1397 n = calloc(1, sizeof(*n));
1404 Each name can be linked to multiple variables defined in different
1405 scopes. Each scope starts where the name is declared and continues
1406 until the end of the containing code block. Scopes of a given name
1407 cannot nest, so a declaration while a name is in-scope is an error.
1409 ###### binding fields
1410 struct variable *var;
1414 struct variable *previous;
1416 struct binding *name;
1417 struct exec *where_decl;// where name was declared
1418 struct exec *where_set; // where type was set
1422 When a scope closes, the values of the variables might need to be freed.
1423 This happens in the context of some `struct exec` and each `exec` will
1424 need to know which variables need to be freed when it completes.
1427 struct variable *to_free;
1429 ####### variable fields
1430 struct exec *cleanup_exec;
1431 struct variable *next_free;
1433 ####### interp exec cleanup
1436 for (v = e->to_free; v; v = v->next_free) {
1437 struct value *val = var_value(c, v);
1438 free_value(v->type, val);
1442 ###### ast functions
1443 static void variable_unlink_exec(struct variable *v)
1445 struct variable **vp;
1446 if (!v->cleanup_exec)
1448 for (vp = &v->cleanup_exec->to_free;
1449 *vp; vp = &(*vp)->next_free) {
1453 v->cleanup_exec = NULL;
1458 While the naming seems strange, we include local constants in the
1459 definition of variables. A name declared `var := value` can
1460 subsequently be changed, but a name declared `var ::= value` cannot -
1463 ###### variable fields
1466 Scopes in parallel branches can be partially merged. More
1467 specifically, if a given name is declared in both branches of an
1468 if/else then its scope is a candidate for merging. Similarly if
1469 every branch of an exhaustive switch (e.g. has an "else" clause)
1470 declares a given name, then the scopes from the branches are
1471 candidates for merging.
1473 Note that names declared inside a loop (which is only parallel to
1474 itself) are never visible after the loop. Similarly names defined in
1475 scopes which are not parallel, such as those started by `for` and
1476 `switch`, are never visible after the scope. Only variables defined in
1477 both `then` and `else` (including the implicit then after an `if`, and
1478 excluding `then` used with `for`) and in all `case`s and `else` of a
1479 `switch` or `while` can be visible beyond the `if`/`switch`/`while`.
1481 Labels, which are a bit like variables, follow different rules.
1482 Labels are not explicitly declared, but if an undeclared name appears
1483 in a context where a label is legal, that effectively declares the
1484 name as a label. The declaration remains in force (or in scope) at
1485 least to the end of the immediately containing block and conditionally
1486 in any larger containing block which does not declare the name in some
1487 other way. Importantly, the conditional scope extension happens even
1488 if the label is only used in one parallel branch of a conditional --
1489 when used in one branch it is treated as having been declared in all
1492 Merge candidates are tentatively visible beyond the end of the
1493 branching statement which creates them. If the name is used, the
1494 merge is affirmed and they become a single variable visible at the
1495 outer layer. If not - if it is redeclared first - the merge lapses.
1497 To track scopes we have an extra stack, implemented as a linked list,
1498 which roughly parallels the parse stack and which is used exclusively
1499 for scoping. When a new scope is opened, a new frame is pushed and
1500 the child-count of the parent frame is incremented. This child-count
1501 is used to distinguish between the first of a set of parallel scopes,
1502 in which declared variables must not be in scope, and subsequent
1503 branches, whether they may already be conditionally scoped.
1505 We need a total ordering of scopes so we can easily compare to variables
1506 to see if they are concurrently in scope. To achieve this we record a
1507 `scope_count` which is actually a count of both beginnings and endings
1508 of scopes. Then each variable has a record of the scope count where it
1509 enters scope, and where it leaves.
1511 To push a new frame *before* any code in the frame is parsed, we need a
1512 grammar reduction. This is most easily achieved with a grammar
1513 element which derives the empty string, and creates the new scope when
1514 it is recognised. This can be placed, for example, between a keyword
1515 like "if" and the code following it.
1519 struct scope *parent;
1523 ###### parse context
1526 struct scope *scope_stack;
1528 ###### variable fields
1529 int scope_start, scope_end;
1531 ###### ast functions
1532 static void scope_pop(struct parse_context *c)
1534 struct scope *s = c->scope_stack;
1536 c->scope_stack = s->parent;
1538 c->scope_depth -= 1;
1539 c->scope_count += 1;
1542 static void scope_push(struct parse_context *c)
1544 struct scope *s = calloc(1, sizeof(*s));
1546 c->scope_stack->child_count += 1;
1547 s->parent = c->scope_stack;
1549 c->scope_depth += 1;
1550 c->scope_count += 1;
1556 OpenScope -> ${ scope_push(c); }$
1558 Each variable records a scope depth and is in one of four states:
1560 - "in scope". This is the case between the declaration of the
1561 variable and the end of the containing block, and also between
1562 the usage with affirms a merge and the end of that block.
1564 The scope depth is not greater than the current parse context scope
1565 nest depth. When the block of that depth closes, the state will
1566 change. To achieve this, all "in scope" variables are linked
1567 together as a stack in nesting order.
1569 - "pending". The "in scope" block has closed, but other parallel
1570 scopes are still being processed. So far, every parallel block at
1571 the same level that has closed has declared the name.
1573 The scope depth is the depth of the last parallel block that
1574 enclosed the declaration, and that has closed.
1576 - "conditionally in scope". The "in scope" block and all parallel
1577 scopes have closed, and no further mention of the name has been seen.
1578 This state includes a secondary nest depth (`min_depth`) which records
1579 the outermost scope seen since the variable became conditionally in
1580 scope. If a use of the name is found, the variable becomes "in scope"
1581 and that secondary depth becomes the recorded scope depth. If the
1582 name is declared as a new variable, the old variable becomes "out of
1583 scope" and the recorded scope depth stays unchanged.
1585 - "out of scope". The variable is neither in scope nor conditionally
1586 in scope. It is permanently out of scope now and can be removed from
1587 the "in scope" stack. When a variable becomes out-of-scope it is
1588 moved to a separate list (`out_scope`) of variables which have fully
1589 known scope. This will be used at the end of each function to assign
1590 each variable a place in the stack frame.
1592 ###### variable fields
1593 int depth, min_depth;
1594 enum { OutScope, PendingScope, CondScope, InScope } scope;
1595 struct variable *in_scope;
1597 ###### parse context
1599 struct variable *in_scope;
1600 struct variable *out_scope;
1602 All variables with the same name are linked together using the
1603 'previous' link. Those variable that have been affirmatively merged all
1604 have a 'merged' pointer that points to one primary variable - the most
1605 recently declared instance. When merging variables, we need to also
1606 adjust the 'merged' pointer on any other variables that had previously
1607 been merged with the one that will no longer be primary.
1609 A variable that is no longer the most recent instance of a name may
1610 still have "pending" scope, if it might still be merged with most
1611 recent instance. These variables don't really belong in the
1612 "in_scope" list, but are not immediately removed when a new instance
1613 is found. Instead, they are detected and ignored when considering the
1614 list of in_scope names.
1616 The storage of the value of a variable will be described later. For now
1617 we just need to know that when a variable goes out of scope, it might
1618 need to be freed. For this we need to be able to find it, so assume that
1619 `var_value()` will provide that.
1621 ###### variable fields
1622 struct variable *merged;
1624 ###### ast functions
1626 static void variable_merge(struct variable *primary, struct variable *secondary)
1630 primary = primary->merged;
1632 for (v = primary->previous; v; v=v->previous)
1633 if (v == secondary || v == secondary->merged ||
1634 v->merged == secondary ||
1635 v->merged == secondary->merged) {
1636 v->scope = OutScope;
1637 v->merged = primary;
1638 if (v->scope_start < primary->scope_start)
1639 primary->scope_start = v->scope_start;
1640 if (v->scope_end > primary->scope_end)
1641 primary->scope_end = v->scope_end; // NOTEST
1642 variable_unlink_exec(v);
1646 ###### forward decls
1647 static struct value *var_value(struct parse_context *c, struct variable *v);
1649 ###### free global vars
1651 while (context.varlist) {
1652 struct binding *b = context.varlist;
1653 struct variable *v = b->var;
1654 context.varlist = b->next;
1657 struct variable *next = v->previous;
1659 if (v->global && v->frame_pos >= 0) {
1660 free_value(v->type, var_value(&context, v));
1661 if (v->depth == 0 && v->type->free == function_free)
1662 // This is a function constant
1663 free_exec(v->where_decl);
1670 #### Manipulating Bindings
1672 When a name is conditionally visible, a new declaration discards the old
1673 binding - the condition lapses. Similarly when we reach the end of a
1674 function (outermost non-global scope) any conditional scope must lapse.
1675 Conversely a usage of the name affirms the visibility and extends it to
1676 the end of the containing block - i.e. the block that contains both the
1677 original declaration and the latest usage. This is determined from
1678 `min_depth`. When a conditionally visible variable gets affirmed like
1679 this, it is also merged with other conditionally visible variables with
1682 When we parse a variable declaration we either report an error if the
1683 name is currently bound, or create a new variable at the current nest
1684 depth if the name is unbound or bound to a conditionally scoped or
1685 pending-scope variable. If the previous variable was conditionally
1686 scoped, it and its homonyms becomes out-of-scope.
1688 When we parse a variable reference (including non-declarative assignment
1689 "foo = bar") we report an error if the name is not bound or is bound to
1690 a pending-scope variable; update the scope if the name is bound to a
1691 conditionally scoped variable; or just proceed normally if the named
1692 variable is in scope.
1694 When we exit a scope, any variables bound at this level are either
1695 marked out of scope or pending-scoped, depending on whether the scope
1696 was sequential or parallel. Here a "parallel" scope means the "then"
1697 or "else" part of a conditional, or any "case" or "else" branch of a
1698 switch. Other scopes are "sequential".
1700 When exiting a parallel scope we check if there are any variables that
1701 were previously pending and are still visible. If there are, then
1702 they weren't redeclared in the most recent scope, so they cannot be
1703 merged and must become out-of-scope. If it is not the first of
1704 parallel scopes (based on `child_count`), we check that there was a
1705 previous binding that is still pending-scope. If there isn't, the new
1706 variable must now be out-of-scope.
1708 When exiting a sequential scope that immediately enclosed parallel
1709 scopes, we need to resolve any pending-scope variables. If there was
1710 no `else` clause, and we cannot determine that the `switch` was exhaustive,
1711 we need to mark all pending-scope variable as out-of-scope. Otherwise
1712 all pending-scope variables become conditionally scoped.
1715 enum closetype { CloseSequential, CloseFunction, CloseParallel, CloseElse };
1717 ###### ast functions
1719 static struct variable *var_decl(struct parse_context *c, struct text s)
1721 struct binding *b = find_binding(c, s);
1722 struct variable *v = b->var;
1724 switch (v ? v->scope : OutScope) {
1726 /* Caller will report the error */
1730 v && v->scope == CondScope;
1732 v->scope = OutScope;
1736 v = calloc(1, sizeof(*v));
1737 v->previous = b->var;
1741 v->min_depth = v->depth = c->scope_depth;
1743 v->in_scope = c->in_scope;
1744 v->scope_start = c->scope_count;
1750 static struct variable *var_ref(struct parse_context *c, struct text s)
1752 struct binding *b = find_binding(c, s);
1753 struct variable *v = b->var;
1754 struct variable *v2;
1756 switch (v ? v->scope : OutScope) {
1759 /* Caller will report the error */
1762 /* All CondScope variables of this name need to be merged
1763 * and become InScope
1765 v->depth = v->min_depth;
1767 for (v2 = v->previous;
1768 v2 && v2->scope == CondScope;
1770 variable_merge(v, v2);
1778 static int var_refile(struct parse_context *c, struct variable *v)
1780 /* Variable just went out of scope. Add it to the out_scope
1781 * list, sorted by ->scope_start
1783 struct variable **vp = &c->out_scope;
1784 while ((*vp) && (*vp)->scope_start < v->scope_start)
1785 vp = &(*vp)->in_scope;
1791 static void var_block_close(struct parse_context *c, enum closetype ct,
1794 /* Close off all variables that are in_scope.
1795 * Some variables in c->scope may already be not-in-scope,
1796 * such as when a PendingScope variable is hidden by a new
1797 * variable with the same name.
1798 * So we check for v->name->var != v and drop them.
1799 * If we choose to make a variable OutScope, we drop it
1802 struct variable *v, **vp, *v2;
1805 for (vp = &c->in_scope;
1806 (v = *vp) && v->min_depth > c->scope_depth;
1807 (v->scope == OutScope || v->name->var != v)
1808 ? (*vp = v->in_scope, var_refile(c, v))
1809 : ( vp = &v->in_scope, 0)) {
1810 v->min_depth = c->scope_depth;
1811 if (v->name->var != v)
1812 /* This is still in scope, but we haven't just
1816 v->min_depth = c->scope_depth;
1817 if (v->scope == InScope)
1818 v->scope_end = c->scope_count;
1819 if (v->scope == InScope && e && !v->global) {
1820 /* This variable gets cleaned up when 'e' finishes */
1821 variable_unlink_exec(v);
1822 v->cleanup_exec = e;
1823 v->next_free = e->to_free;
1828 case CloseParallel: /* handle PendingScope */
1832 if (c->scope_stack->child_count == 1)
1833 /* first among parallel branches */
1834 v->scope = PendingScope;
1835 else if (v->previous &&
1836 v->previous->scope == PendingScope)
1837 /* all previous branches used name */
1838 v->scope = PendingScope;
1839 else if (v->type == Tlabel)
1840 /* Labels remain pending even when not used */
1841 v->scope = PendingScope; // UNTESTED
1843 v->scope = OutScope;
1844 if (ct == CloseElse) {
1845 /* All Pending variables with this name
1846 * are now Conditional */
1848 v2 && v2->scope == PendingScope;
1850 v2->scope = CondScope;
1854 /* Not possible as it would require
1855 * parallel scope to be nested immediately
1856 * in a parallel scope, and that never
1860 /* Not possible as we already tested for
1867 if (v->scope == CondScope)
1868 /* Condition cannot continue past end of function */
1871 case CloseSequential:
1872 if (v->type == Tlabel)
1873 v->scope = PendingScope;
1876 v->scope = OutScope;
1879 /* There was no 'else', so we can only become
1880 * conditional if we know the cases were exhaustive,
1881 * and that doesn't mean anything yet.
1882 * So only labels become conditional..
1885 v2 && v2->scope == PendingScope;
1887 if (v2->type == Tlabel)
1888 v2->scope = CondScope;
1890 v2->scope = OutScope;
1893 case OutScope: break;
1902 The value of a variable is store separately from the variable, on an
1903 analogue of a stack frame. There are (currently) two frames that can be
1904 active. A global frame which currently only stores constants, and a
1905 stacked frame which stores local variables. Each variable knows if it
1906 is global or not, and what its index into the frame is.
1908 Values in the global frame are known immediately they are relevant, so
1909 the frame needs to be reallocated as it grows so it can store those
1910 values. The local frame doesn't get values until the interpreted phase
1911 is started, so there is no need to allocate until the size is known.
1913 We initialize the `frame_pos` to an impossible value, so that we can
1914 tell if it was set or not later.
1916 ###### variable fields
1920 ###### variable init
1923 ###### parse context
1925 short global_size, global_alloc;
1927 void *global, *local;
1929 ###### forward decls
1930 static struct value *global_alloc(struct parse_context *c, struct type *t,
1931 struct variable *v, struct value *init);
1933 ###### ast functions
1935 static struct value *var_value(struct parse_context *c, struct variable *v)
1938 if (!c->local || !v->type)
1939 return NULL; // UNTESTED
1940 if (v->frame_pos + v->type->size > c->local_size) {
1941 printf("INVALID frame_pos\n"); // NOTEST
1944 return c->local + v->frame_pos;
1946 if (c->global_size > c->global_alloc) {
1947 int old = c->global_alloc;
1948 c->global_alloc = (c->global_size | 1023) + 1024;
1949 c->global = realloc(c->global, c->global_alloc);
1950 memset(c->global + old, 0, c->global_alloc - old);
1952 return c->global + v->frame_pos;
1955 static struct value *global_alloc(struct parse_context *c, struct type *t,
1956 struct variable *v, struct value *init)
1959 struct variable scratch;
1961 if (t->prepare_type)
1962 t->prepare_type(c, t, 1); // NOTEST
1964 if (c->global_size & (t->align - 1))
1965 c->global_size = (c->global_size + t->align) & ~(t->align-1); // NOTEST
1970 v->frame_pos = c->global_size;
1972 c->global_size += v->type->size;
1973 ret = var_value(c, v);
1975 memcpy(ret, init, t->size);
1981 As global values are found -- struct field initializers, labels etc --
1982 `global_alloc()` is called to record the value in the global frame.
1984 When the program is fully parsed, each function is analysed, we need to
1985 walk the list of variables local to that function and assign them an
1986 offset in the stack frame. For this we have `scope_finalize()`.
1988 We keep the stack from dense by re-using space for between variables
1989 that are not in scope at the same time. The `out_scope` list is sorted
1990 by `scope_start` and as we process a varible, we move it to an FIFO
1991 stack. For each variable we consider, we first discard any from the
1992 stack anything that went out of scope before the new variable came in.
1993 Then we place the new variable just after the one at the top of the
1996 ###### ast functions
1998 static void scope_finalize(struct parse_context *c, struct type *ft)
2000 int size = ft->function.local_size;
2001 struct variable *next = ft->function.scope;
2002 struct variable *done = NULL;
2005 struct variable *v = next;
2006 struct type *t = v->type;
2013 if (v->frame_pos >= 0)
2015 while (done && done->scope_end < v->scope_start)
2016 done = done->in_scope;
2018 pos = done->frame_pos + done->type->size;
2020 pos = ft->function.local_size;
2021 if (pos & (t->align - 1))
2022 pos = (pos + t->align) & ~(t->align-1);
2024 if (size < pos + v->type->size)
2025 size = pos + v->type->size;
2029 c->out_scope = NULL;
2030 ft->function.local_size = size;
2033 ###### free context storage
2034 free(context.global);
2036 #### Variables as executables
2038 Just as we used a `val` to wrap a value into an `exec`, we similarly
2039 need a `var` to wrap a `variable` into an exec. While each `val`
2040 contained a copy of the value, each `var` holds a link to the variable
2041 because it really is the same variable no matter where it appears.
2042 When a variable is used, we need to remember to follow the `->merged`
2043 link to find the primary instance.
2045 When a variable is declared, it may or may not be given an explicit
2046 type. We need to record which so that we can report the parsed code
2055 struct variable *var;
2058 ###### variable fields
2066 VariableDecl -> IDENTIFIER : ${ {
2067 struct variable *v = var_decl(c, $1.txt);
2068 $0 = new_pos(var, $1);
2073 v = var_ref(c, $1.txt);
2075 type_err(c, "error: variable '%v' redeclared",
2077 type_err(c, "info: this is where '%v' was first declared",
2078 v->where_decl, NULL, 0, NULL);
2081 | IDENTIFIER :: ${ {
2082 struct variable *v = var_decl(c, $1.txt);
2083 $0 = new_pos(var, $1);
2089 v = var_ref(c, $1.txt);
2091 type_err(c, "error: variable '%v' redeclared",
2093 type_err(c, "info: this is where '%v' was first declared",
2094 v->where_decl, NULL, 0, NULL);
2097 | IDENTIFIER : Type ${ {
2098 struct variable *v = var_decl(c, $1.txt);
2099 $0 = new_pos(var, $1);
2105 v->explicit_type = 1;
2107 v = var_ref(c, $1.txt);
2109 type_err(c, "error: variable '%v' redeclared",
2111 type_err(c, "info: this is where '%v' was first declared",
2112 v->where_decl, NULL, 0, NULL);
2115 | IDENTIFIER :: Type ${ {
2116 struct variable *v = var_decl(c, $1.txt);
2117 $0 = new_pos(var, $1);
2124 v->explicit_type = 1;
2126 v = var_ref(c, $1.txt);
2128 type_err(c, "error: variable '%v' redeclared",
2130 type_err(c, "info: this is where '%v' was first declared",
2131 v->where_decl, NULL, 0, NULL);
2136 Variable -> IDENTIFIER ${ {
2137 struct variable *v = var_ref(c, $1.txt);
2138 $0 = new_pos(var, $1);
2140 /* This might be a global const or a label
2141 * Allocate a var with impossible type Tnone,
2142 * which will be adjusted when we find out what it is,
2143 * or will trigger an error.
2145 v = var_decl(c, $1.txt);
2152 cast(var, $0)->var = v;
2155 ###### print exec cases
2158 struct var *v = cast(var, e);
2160 struct binding *b = v->var->name;
2161 printf("%.*s", b->name.len, b->name.txt);
2168 if (loc && loc->type == Xvar) {
2169 struct var *v = cast(var, loc);
2171 struct binding *b = v->var->name;
2172 fprintf(stderr, "%.*s", b->name.len, b->name.txt);
2174 fputs("???", stderr); // NOTEST
2176 fputs("NOTVAR", stderr); // NOTEST
2179 ###### propagate exec cases
2183 struct var *var = cast(var, prog);
2184 struct variable *v = var->var;
2186 type_err(c, "%d:BUG: no variable!!", prog, NULL, 0, NULL); // NOTEST
2187 return Tnone; // NOTEST
2190 if (v->constant && (rules & Rnoconstant)) {
2191 type_err(c, "error: Cannot assign to a constant: %v",
2192 prog, NULL, 0, NULL);
2193 type_err(c, "info: name was defined as a constant here",
2194 v->where_decl, NULL, 0, NULL);
2197 if (v->type == Tnone && v->where_decl == prog)
2198 type_err(c, "error: variable used but not declared: %v",
2199 prog, NULL, 0, NULL);
2200 if (v->type == NULL) {
2201 if (type && !(*perr & Efail)) {
2203 v->where_set = prog;
2206 } else if (!type_compat(type, v->type, rules)) {
2207 type_err(c, "error: expected %1%r but variable '%v' is %2", prog,
2208 type, rules, v->type);
2209 type_err(c, "info: this is where '%v' was set to %1", v->where_set,
2210 v->type, rules, NULL);
2212 if (!v->global || v->frame_pos < 0)
2219 ###### interp exec cases
2222 struct var *var = cast(var, e);
2223 struct variable *v = var->var;
2226 lrv = var_value(c, v);
2231 ###### ast functions
2233 static void free_var(struct var *v)
2238 ###### free exec cases
2239 case Xvar: free_var(cast(var, e)); break;
2244 Now that we have the shape of the interpreter in place we can add some
2245 complex types and connected them in to the data structures and the
2246 different phases of parse, analyse, print, interpret.
2248 Being "complex" the language will naturally have syntax to access
2249 specifics of objects of these types. These will fit into the grammar as
2250 "Terms" which are the things that are combined with various operators to
2251 form "Expression". Where a Term is formed by some operation on another
2252 Term, the subordinate Term will always come first, so for example a
2253 member of an array will be expressed as the Term for the array followed
2254 by an index in square brackets. The strict rule of using postfix
2255 operations makes precedence irrelevant within terms. To provide a place
2256 to put the grammar for each terms of each type, we will start out by
2257 introducing the "Term" grammar production, with contains at least a
2258 simple "Value" (to be explained later).
2262 Term -> Value ${ $0 = $<1; }$
2263 | Variable ${ $0 = $<1; }$
2266 Thus far the complex types we have are arrays and structs.
2270 Arrays can be declared by giving a size and a type, as `[size]type' so
2271 `freq:[26]number` declares `freq` to be an array of 26 numbers. The
2272 size can be either a literal number, or a named constant. Some day an
2273 arbitrary expression will be supported.
2275 As a formal parameter to a function, the array can be declared with a
2276 new variable as the size: `name:[size::number]string`. The `size`
2277 variable is set to the size of the array and must be a constant. As
2278 `number` is the only supported type, it can be left out:
2279 `name:[size::]string`.
2281 Arrays cannot be assigned. When pointers are introduced we will also
2282 introduce array slices which can refer to part or all of an array -
2283 the assignment syntax will create a slice. For now, an array can only
2284 ever be referenced by the name it is declared with. It is likely that
2285 a "`copy`" primitive will eventually be define which can be used to
2286 make a copy of an array with controllable recursive depth.
2288 For now we have two sorts of array, those with fixed size either because
2289 it is given as a literal number or because it is a struct member (which
2290 cannot have a runtime-changing size), and those with a size that is
2291 determined at runtime - local variables with a const size. The former
2292 have their size calculated at parse time, the latter at run time.
2294 For the latter type, the `size` field of the type is the size of a
2295 pointer, and the array is reallocated every time it comes into scope.
2297 We differentiate struct fields with a const size from local variables
2298 with a const size by whether they are prepared at parse time or not.
2300 ###### type union fields
2303 int unspec; // size is unspecified - vsize must be set.
2306 struct variable *vsize;
2307 struct type *member;
2310 ###### value union fields
2311 void *array; // used if not static_size
2313 ###### value functions
2315 static int array_prepare_type(struct parse_context *c, struct type *type,
2318 struct value *vsize;
2320 if (type->array.static_size)
2321 return 1; // UNTESTED
2322 if (type->array.unspec && parse_time)
2323 return 1; // UNTESTED
2324 if (parse_time && type->array.vsize && !type->array.vsize->global)
2325 return 1; // UNTESTED
2327 if (type->array.vsize) {
2328 vsize = var_value(c, type->array.vsize);
2330 return 1; // UNTESTED
2332 mpz_tdiv_q(q, mpq_numref(vsize->num), mpq_denref(vsize->num));
2333 type->array.size = mpz_get_si(q);
2338 if (type->array.member->size <= 0)
2339 return 0; // UNTESTED
2341 type->array.static_size = 1;
2342 type->size = type->array.size * type->array.member->size;
2343 type->align = type->array.member->align;
2348 static void array_init(struct type *type, struct value *val)
2351 void *ptr = val->ptr;
2355 if (!type->array.static_size) {
2356 val->array = calloc(type->array.size,
2357 type->array.member->size);
2360 for (i = 0; i < type->array.size; i++) {
2362 v = (void*)ptr + i * type->array.member->size;
2363 val_init(type->array.member, v);
2367 static void array_free(struct type *type, struct value *val)
2370 void *ptr = val->ptr;
2372 if (!type->array.static_size)
2374 for (i = 0; i < type->array.size; i++) {
2376 v = (void*)ptr + i * type->array.member->size;
2377 free_value(type->array.member, v);
2379 if (!type->array.static_size)
2383 static int array_compat(struct type *require, struct type *have)
2385 if (have->compat != require->compat)
2387 /* Both are arrays, so we can look at details */
2388 if (!type_compat(require->array.member, have->array.member, 0))
2390 if (have->array.unspec && require->array.unspec) {
2391 if (have->array.vsize && require->array.vsize &&
2392 have->array.vsize != require->array.vsize) // UNTESTED
2393 /* sizes might not be the same */
2394 return 0; // UNTESTED
2397 if (have->array.unspec || require->array.unspec)
2398 return 1; // UNTESTED
2399 if (require->array.vsize == NULL && have->array.vsize == NULL)
2400 return require->array.size == have->array.size;
2402 return require->array.vsize == have->array.vsize; // UNTESTED
2405 static void array_print_type(struct type *type, FILE *f)
2408 if (type->array.vsize) {
2409 struct binding *b = type->array.vsize->name;
2410 fprintf(f, "%.*s%s]", b->name.len, b->name.txt,
2411 type->array.unspec ? "::" : "");
2412 } else if (type->array.size)
2413 fprintf(f, "%d]", type->array.size);
2416 type_print(type->array.member, f);
2419 static struct type array_prototype = {
2421 .prepare_type = array_prepare_type,
2422 .print_type = array_print_type,
2423 .compat = array_compat,
2425 .size = sizeof(void*),
2426 .align = sizeof(void*),
2429 ###### declare terminals
2434 | [ NUMBER ] Type ${ {
2440 if (number_parse(num, tail, $2.txt) == 0)
2441 tok_err(c, "error: unrecognised number", &$2);
2443 tok_err(c, "error: unsupported number suffix", &$2);
2446 elements = mpz_get_ui(mpq_numref(num));
2447 if (mpz_cmp_ui(mpq_denref(num), 1) != 0) {
2448 tok_err(c, "error: array size must be an integer",
2450 } else if (mpz_cmp_ui(mpq_numref(num), 1UL << 30) >= 0)
2451 tok_err(c, "error: array size is too large",
2456 $0 = t = add_anon_type(c, &array_prototype, "array[%d]", elements );
2457 t->array.size = elements;
2458 t->array.member = $<4;
2459 t->array.vsize = NULL;
2462 | [ IDENTIFIER ] Type ${ {
2463 struct variable *v = var_ref(c, $2.txt);
2466 tok_err(c, "error: name undeclared", &$2);
2467 else if (!v->constant)
2468 tok_err(c, "error: array size must be a constant", &$2);
2470 $0 = add_anon_type(c, &array_prototype, "array[%.*s]", $2.txt.len, $2.txt.txt);
2471 $0->array.member = $<4;
2473 $0->array.vsize = v;
2478 OptType -> Type ${ $0 = $<1; }$
2481 ###### formal type grammar
2483 | [ IDENTIFIER :: OptType ] Type ${ {
2484 struct variable *v = var_decl(c, $ID.txt);
2490 $0 = add_anon_type(c, &array_prototype, "array[var]");
2491 $0->array.member = $<6;
2493 $0->array.unspec = 1;
2494 $0->array.vsize = v;
2502 | Term [ Expression ] ${ {
2503 struct binode *b = new(binode);
2510 ###### print binode cases
2512 print_exec(b->left, -1, bracket);
2514 print_exec(b->right, -1, bracket);
2518 ###### propagate binode cases
2520 /* left must be an array, right must be a number,
2521 * result is the member type of the array
2523 propagate_types(b->right, c, perr, Tnum, 0);
2524 t = propagate_types(b->left, c, perr, NULL, rules & Rnoconstant);
2525 if (!t || t->compat != array_compat) {
2526 type_err(c, "error: %1 cannot be indexed", prog, t, 0, NULL);
2529 if (!type_compat(type, t->array.member, rules)) {
2530 type_err(c, "error: have %1 but need %2", prog,
2531 t->array.member, rules, type);
2533 return t->array.member;
2537 ###### interp binode cases
2543 lleft = linterp_exec(c, b->left, <ype);
2544 right = interp_exec(c, b->right, &rtype);
2546 mpz_tdiv_q(q, mpq_numref(right.num), mpq_denref(right.num));
2550 if (ltype->array.static_size)
2553 ptr = *(void**)lleft;
2554 rvtype = ltype->array.member;
2555 if (i >= 0 && i < ltype->array.size)
2556 lrv = ptr + i * rvtype->size;
2558 val_init(ltype->array.member, &rv); // UNSAFE
2565 A `struct` is a data-type that contains one or more other data-types.
2566 It differs from an array in that each member can be of a different
2567 type, and they are accessed by name rather than by number. Thus you
2568 cannot choose an element by calculation, you need to know what you
2571 The language makes no promises about how a given structure will be
2572 stored in memory - it is free to rearrange fields to suit whatever
2573 criteria seems important.
2575 Structs are declared separately from program code - they cannot be
2576 declared in-line in a variable declaration like arrays can. A struct
2577 is given a name and this name is used to identify the type - the name
2578 is not prefixed by the word `struct` as it would be in C.
2580 Structs are only treated as the same if they have the same name.
2581 Simply having the same fields in the same order is not enough. This
2582 might change once we can create structure initializers from a list of
2585 Each component datum is identified much like a variable is declared,
2586 with a name, one or two colons, and a type. The type cannot be omitted
2587 as there is no opportunity to deduce the type from usage. An initial
2588 value can be given following an equals sign, so
2590 ##### Example: a struct type
2596 would declare a type called "complex" which has two number fields,
2597 each initialised to zero.
2599 Struct will need to be declared separately from the code that uses
2600 them, so we will need to be able to print out the declaration of a
2601 struct when reprinting the whole program. So a `print_type_decl` type
2602 function will be needed.
2604 ###### type union fields
2613 } *fields; // This is created when field_list is analysed.
2615 struct fieldlist *prev;
2618 } *field_list; // This is created during parsing
2621 ###### type functions
2622 void (*print_type_decl)(struct type *type, FILE *f);
2624 ###### value functions
2626 static void structure_init(struct type *type, struct value *val)
2630 for (i = 0; i < type->structure.nfields; i++) {
2632 v = (void*) val->ptr + type->structure.fields[i].offset;
2633 if (type->structure.fields[i].init)
2634 dup_value(type->structure.fields[i].type,
2635 type->structure.fields[i].init,
2638 val_init(type->structure.fields[i].type, v);
2642 static void structure_free(struct type *type, struct value *val)
2646 for (i = 0; i < type->structure.nfields; i++) {
2648 v = (void*)val->ptr + type->structure.fields[i].offset;
2649 free_value(type->structure.fields[i].type, v);
2653 static void free_fieldlist(struct fieldlist *f)
2657 free_fieldlist(f->prev);
2662 static void structure_free_type(struct type *t)
2665 for (i = 0; i < t->structure.nfields; i++)
2666 if (t->structure.fields[i].init) {
2667 free_value(t->structure.fields[i].type,
2668 t->structure.fields[i].init);
2670 free(t->structure.fields);
2671 free_fieldlist(t->structure.field_list);
2674 static int structure_prepare_type(struct parse_context *c,
2675 struct type *t, int parse_time)
2678 struct fieldlist *f;
2680 if (!parse_time || t->structure.fields)
2683 for (f = t->structure.field_list; f; f=f->prev) {
2687 if (f->f.type->size <= 0)
2689 if (f->f.type->prepare_type)
2690 f->f.type->prepare_type(c, f->f.type, parse_time);
2692 if (f->init == NULL)
2696 propagate_types(f->init, c, &perr, f->f.type, 0);
2697 } while (perr & Eretry);
2699 c->parse_error += 1; // NOTEST
2702 t->structure.nfields = cnt;
2703 t->structure.fields = calloc(cnt, sizeof(struct field));
2704 f = t->structure.field_list;
2706 int a = f->f.type->align;
2708 t->structure.fields[cnt] = f->f;
2709 if (t->size & (a-1))
2710 t->size = (t->size | (a-1)) + 1;
2711 t->structure.fields[cnt].offset = t->size;
2712 t->size += ((f->f.type->size - 1) | (a-1)) + 1;
2716 if (f->init && !c->parse_error) {
2717 struct value vl = interp_exec(c, f->init, NULL);
2718 t->structure.fields[cnt].init =
2719 global_alloc(c, f->f.type, NULL, &vl);
2727 static struct type structure_prototype = {
2728 .init = structure_init,
2729 .free = structure_free,
2730 .free_type = structure_free_type,
2731 .print_type_decl = structure_print_type,
2732 .prepare_type = structure_prepare_type,
2745 enum { IndexUnknown = -1, IndexInvalid = -2 };
2747 ###### free exec cases
2749 free_exec(cast(fieldref, e)->left);
2753 ###### declare terminals
2758 | Term . IDENTIFIER ${ {
2759 struct fieldref *fr = new_pos(fieldref, $2);
2762 fr->index = IndexUnknown;
2766 ###### print exec cases
2770 struct fieldref *f = cast(fieldref, e);
2771 print_exec(f->left, -1, bracket);
2772 printf(".%.*s", f->name.len, f->name.txt);
2776 ###### ast functions
2777 static int find_struct_index(struct type *type, struct text field)
2780 for (i = 0; i < type->structure.nfields; i++)
2781 if (text_cmp(type->structure.fields[i].name, field) == 0)
2783 return IndexInvalid;
2786 ###### propagate exec cases
2790 struct fieldref *f = cast(fieldref, prog);
2791 struct type *st = propagate_types(f->left, c, perr, NULL, 0);
2794 type_err(c, "error: unknown type for field access", f->left, // UNTESTED
2796 else if (st->init != structure_init)
2797 type_err(c, "error: field reference attempted on %1, not a struct",
2798 f->left, st, 0, NULL);
2799 else if (f->index == IndexUnknown) {
2800 f->index = find_struct_index(st, f->name);
2802 type_err(c, "error: cannot find requested field in %1",
2803 f->left, st, 0, NULL);
2805 if (f->index >= 0) {
2806 struct type *ft = st->structure.fields[f->index].type;
2807 if (!type_compat(type, ft, rules))
2808 type_err(c, "error: have %1 but need %2", prog,
2815 ###### interp exec cases
2818 struct fieldref *f = cast(fieldref, e);
2820 struct value *lleft = linterp_exec(c, f->left, <ype);
2821 lrv = (void*)lleft->ptr + ltype->structure.fields[f->index].offset;
2822 rvtype = ltype->structure.fields[f->index].type;
2826 ###### top level grammar
2827 DeclareStruct -> struct IDENTIFIER FieldBlock Newlines ${ {
2829 t = find_type(c, $ID.txt);
2831 t = add_type(c, $ID.txt, &structure_prototype);
2832 else if (t->size >= 0) {
2833 tok_err(c, "error: type already declared", &$ID);
2834 tok_err(c, "info: this is location of declartion", &t->first_use);
2835 /* Create a new one - duplicate */
2836 t = add_type(c, $ID.txt, &structure_prototype);
2838 struct type tmp = *t;
2839 *t = structure_prototype;
2843 t->structure.field_list = $<FB;
2848 FieldBlock -> { IN OptNL FieldLines OUT OptNL } ${ $0 = $<FL; }$
2849 | { SimpleFieldList } ${ $0 = $<SFL; }$
2850 | IN OptNL FieldLines OUT ${ $0 = $<FL; }$
2851 | SimpleFieldList EOL ${ $0 = $<SFL; }$
2853 FieldLines -> SimpleFieldList Newlines ${ $0 = $<SFL; }$
2854 | FieldLines SimpleFieldList Newlines ${
2859 SimpleFieldList -> Field ${ $0 = $<F; }$
2860 | SimpleFieldList ; Field ${
2864 | SimpleFieldList ; ${
2867 | ERROR ${ tok_err(c, "Syntax error in struct field", &$1); }$
2869 Field -> IDENTIFIER : Type = Expression ${ {
2870 $0 = calloc(1, sizeof(struct fieldlist));
2871 $0->f.name = $ID.txt;
2872 $0->f.type = $<Type;
2876 | IDENTIFIER : Type ${
2877 $0 = calloc(1, sizeof(struct fieldlist));
2878 $0->f.name = $ID.txt;
2879 $0->f.type = $<Type;
2882 ###### forward decls
2883 static void structure_print_type(struct type *t, FILE *f);
2885 ###### value functions
2886 static void structure_print_type(struct type *t, FILE *f)
2890 fprintf(f, "struct %.*s\n", t->name.len, t->name.txt);
2892 for (i = 0; i < t->structure.nfields; i++) {
2893 struct field *fl = t->structure.fields + i;
2894 fprintf(f, " %.*s : ", fl->name.len, fl->name.txt);
2895 type_print(fl->type, f);
2896 if (fl->type->print && fl->init) {
2898 if (fl->type == Tstr)
2899 fprintf(f, "\""); // UNTESTED
2900 print_value(fl->type, fl->init, f);
2901 if (fl->type == Tstr)
2902 fprintf(f, "\""); // UNTESTED
2908 ###### print type decls
2913 while (target != 0) {
2915 for (t = context.typelist; t ; t=t->next)
2916 if (!t->anon && t->print_type_decl &&
2926 t->print_type_decl(t, stdout);
2934 References, or pointers, are values that refer to another value. They
2935 can only refer to a `struct`, though as a struct can embed anything they
2936 can effectively refer to anything.
2938 References are potentially dangerous as they might refer to some
2939 variable which no longer exists - either because a stack frame
2940 containing it has been discarded or because the value was allocated on
2941 the heap and has now been free. Ocean does not yet provide any
2942 protection against these problems. It will in due course.
2944 With references comes the opportunity and the need to explicitly
2945 allocate values on the "heap" and to free them. We currently provide
2946 fairly basic support for this.
2948 Reference make use of the `@` symbol in various ways. A type that starts
2949 with `@` is a reference to whatever follows. A reference value
2950 followed by an `@` acts as the referred value, though the `@` is often
2951 not needed. Finally, an expression that starts with `@` is a special
2952 reference related expression. Some examples might help.
2954 ##### Example: Reference examples
2961 bar.number = 23; bar.string = "hello"
2972 Obviously this is very contrived. `ref` is a reference to a `foo` which
2973 is initially set to refer to the value stored in `bar` - no extra syntax
2974 is needed to "Take the address of" `bar` - the fact that `ref` is a
2975 reference means that only the address make sense.
2977 When `ref.a` is accessed, that is whatever value is stored in `bar.a`.
2978 The same syntax is used for accessing fields both in structs and in
2979 references to structs. It would be correct to use `ref@.a`, but not
2982 `@new()` creates an object of whatever type is needed for the program
2983 to by type-correct. In future iterations of Ocean, arguments a
2984 constructor will access arguments, so the the syntax now looks like a
2985 function call. `@free` can be assigned any reference that was returned
2986 by `@new()`, and it will be freed. `@nil` is a value of whatever
2987 reference type is appropriate, and is stable and never the address of
2988 anything in the heap or on the stack. A reference can be assigned
2989 `@nil` or compared against that value.
2991 ###### declare terminals
2994 ###### type union fields
2997 struct type *referent;
3000 ###### value union fields
3003 ###### value functions
3005 static void reference_print_type(struct type *t, FILE *f)
3008 type_print(t->reference.referent, f);
3011 static int reference_cmp(struct type *tl, struct type *tr,
3012 struct value *left, struct value *right)
3014 return left->ref == right->ref ? 0 : 1;
3017 static void reference_dup(struct type *t,
3018 struct value *vold, struct value *vnew)
3020 vnew->ref = vold->ref;
3023 static void reference_free(struct type *t, struct value *v)
3025 /* Nothing to do here */
3028 static int reference_compat(struct type *require, struct type *have)
3030 if (have->compat != require->compat)
3032 if (have->reference.referent != require->reference.referent)
3037 static int reference_test(struct type *type, struct value *val)
3039 return val->ref != NULL;
3042 static struct type reference_prototype = {
3043 .print_type = reference_print_type,
3044 .cmp_eq = reference_cmp,
3045 .dup = reference_dup,
3046 .test = reference_test,
3047 .free = reference_free,
3048 .compat = reference_compat,
3049 .size = sizeof(void*),
3050 .align = sizeof(void*),
3056 struct type *t = find_type(c, $ID.txt);
3058 t = add_type(c, $ID.txt, NULL);
3061 $0 = find_anon_type(c, &reference_prototype, "@%.*s",
3062 $ID.txt.len, $ID.txt.txt);
3063 $0->reference.referent = t;
3066 ###### core functions
3067 static int text_is(struct text t, char *s)
3069 return (strlen(s) == t.len &&
3070 strncmp(s, t.txt, t.len) == 0);
3079 enum ref_func { RefNew, RefFree, RefNil } action;
3080 struct type *reftype;
3084 ###### SimpleStatement Grammar
3086 | @ IDENTIFIER = Expression ${ {
3087 struct ref *r = new_pos(ref, $ID);
3089 if (!text_is($ID.txt, "free"))
3090 tok_err(c, "error: only \"@free\" makes sense here",
3094 r->action = RefFree;
3098 ###### expression grammar
3099 | @ IDENTIFIER ( ) ${
3100 // Only 'new' valid here
3101 if (!text_is($ID.txt, "new")) {
3102 tok_err(c, "error: Only reference function is \"@new()\"",
3105 struct ref *r = new_pos(ref,$ID);
3111 // Only 'nil' valid here
3112 if (!text_is($ID.txt, "nil")) {
3113 tok_err(c, "error: Only reference value is \"@nil\"",
3116 struct ref *r = new_pos(ref,$ID);
3122 ###### print exec cases
3124 struct ref *r = cast(ref, e);
3125 switch (r->action) {
3127 printf("@new()"); break;
3129 printf("@nil"); break;
3131 do_indent(indent, "@free = ");
3132 print_exec(r->right, indent, bracket);
3138 ###### propagate exec cases
3140 struct ref *r = cast(ref, prog);
3141 switch (r->action) {
3143 if (type && type->free != reference_free) {
3144 type_err(c, "error: @new() can only be used with references, not %1",
3145 prog, type, 0, NULL);
3148 if (type && !r->reftype) {
3154 if (type && type->free != reference_free)
3155 type_err(c, "error: @nil can only be used with reference, not %1",
3156 prog, type, 0, NULL);
3157 if (type && !r->reftype) {
3163 t = propagate_types(r->right, c, perr, NULL, 0);
3164 if (t && t->free != reference_free)
3165 type_err(c, "error: @free can only be assigned a reference, not %1",
3174 ###### interp exec cases
3176 struct ref *r = cast(ref, e);
3177 switch (r->action) {
3180 rv.ref = calloc(1, r->reftype->reference.referent->size);
3181 rvtype = r->reftype;
3185 rvtype = r->reftype;
3188 rv = interp_exec(c, r->right, &rvtype);
3189 free_value(rvtype->reference.referent, rv.ref);
3197 ###### free exec cases
3199 struct ref *r = cast(ref, e);
3200 free_exec(r->right);
3205 ###### Expressions: dereference
3213 struct binode *b = new(binode);
3219 ###### print binode cases
3221 print_exec(b->left, -1, bracket);
3225 ###### propagate binode cases
3227 /* left must be a reference, and we return what it refers to */
3228 /* FIXME how can I pass the expected type down? */
3229 t = propagate_types(b->left, c, perr, NULL, 0);
3230 if (!t || t->free != reference_free)
3231 type_err(c, "error: Cannot dereference %1", b, t, 0, NULL);
3233 return t->reference.referent;
3236 ###### interp binode cases
3238 left = interp_exec(c, b->left, <ype);
3240 rvtype = ltype->reference.referent;
3247 A function is a chunk of code which can be passed parameters and can
3248 return results. Each function has a type which includes the set of
3249 parameters and the return value. As yet these types cannot be declared
3250 separately from the function itself.
3252 The parameters can be specified either in parentheses as a ';' separated
3255 ##### Example: function 1
3257 func main(av:[ac::number]string; env:[envc::number]string)
3260 or as an indented list of one parameter per line (though each line can
3261 be a ';' separated list)
3263 ##### Example: function 2
3266 argv:[argc::number]string
3267 env:[envc::number]string
3271 In the first case a return type can follow the parentheses after a colon,
3272 in the second it is given on a line starting with the word `return`.
3274 ##### Example: functions that return
3276 func add(a:number; b:number): number
3286 Rather than returning a type, the function can specify a set of local
3287 variables to return as a struct. The values of these variables when the
3288 function exits will be provided to the caller. For this the return type
3289 is replaced with a block of result declarations, either in parentheses
3290 or bracketed by `return` and `do`.
3292 ##### Example: functions returning multiple variables
3294 func to_cartesian(rho:number; theta:number):(x:number; y:number)
3307 For constructing the lists we use a `List` binode, which will be
3308 further detailed when Expression Lists are introduced.
3310 ###### type union fields
3313 struct binode *params;
3314 struct type *return_type;
3315 struct variable *scope;
3316 int inline_result; // return value is at start of 'local'
3320 ###### value union fields
3321 struct exec *function;
3323 ###### type functions
3324 void (*check_args)(struct parse_context *c, enum prop_err *perr,
3325 struct type *require, struct exec *args);
3327 ###### value functions
3329 static void function_free(struct type *type, struct value *val)
3331 free_exec(val->function);
3332 val->function = NULL;
3335 static int function_compat(struct type *require, struct type *have)
3337 // FIXME can I do anything here yet?
3341 static void function_check_args(struct parse_context *c, enum prop_err *perr,
3342 struct type *require, struct exec *args)
3344 /* This should be 'compat', but we don't have a 'tuple' type to
3345 * hold the type of 'args'
3347 struct binode *arg = cast(binode, args);
3348 struct binode *param = require->function.params;
3351 struct var *pv = cast(var, param->left);
3353 type_err(c, "error: insufficient arguments to function.",
3354 args, NULL, 0, NULL);
3358 propagate_types(arg->left, c, perr, pv->var->type, 0);
3359 param = cast(binode, param->right);
3360 arg = cast(binode, arg->right);
3363 type_err(c, "error: too many arguments to function.",
3364 args, NULL, 0, NULL);
3367 static void function_print(struct type *type, struct value *val, FILE *f)
3369 print_exec(val->function, 1, 0);
3372 static void function_print_type_decl(struct type *type, FILE *f)
3376 for (b = type->function.params; b; b = cast(binode, b->right)) {
3377 struct variable *v = cast(var, b->left)->var;
3378 fprintf(f, "%.*s%s", v->name->name.len, v->name->name.txt,
3379 v->constant ? "::" : ":");
3380 type_print(v->type, f);
3385 if (type->function.return_type != Tnone) {
3387 if (type->function.inline_result) {
3389 struct type *t = type->function.return_type;
3391 for (i = 0; i < t->structure.nfields; i++) {
3392 struct field *fl = t->structure.fields + i;
3395 fprintf(f, "%.*s:", fl->name.len, fl->name.txt);
3396 type_print(fl->type, f);
3400 type_print(type->function.return_type, f);
3405 static void function_free_type(struct type *t)
3407 free_exec(t->function.params);
3410 static struct type function_prototype = {
3411 .size = sizeof(void*),
3412 .align = sizeof(void*),
3413 .free = function_free,
3414 .compat = function_compat,
3415 .check_args = function_check_args,
3416 .print = function_print,
3417 .print_type_decl = function_print_type_decl,
3418 .free_type = function_free_type,
3421 ###### declare terminals
3431 FuncName -> IDENTIFIER ${ {
3432 struct variable *v = var_decl(c, $1.txt);
3433 struct var *e = new_pos(var, $1);
3440 v = var_ref(c, $1.txt);
3442 type_err(c, "error: function '%v' redeclared",
3444 type_err(c, "info: this is where '%v' was first declared",
3445 v->where_decl, NULL, 0, NULL);
3451 Args -> ArgsLine NEWLINE ${ $0 = $<AL; }$
3452 | Args ArgsLine NEWLINE ${ {
3453 struct binode *b = $<AL;
3454 struct binode **bp = &b;
3456 bp = (struct binode **)&(*bp)->left;
3461 ArgsLine -> ${ $0 = NULL; }$
3462 | Varlist ${ $0 = $<1; }$
3463 | Varlist ; ${ $0 = $<1; }$
3465 Varlist -> Varlist ; ArgDecl ${
3466 $0 = new_pos(binode, $2);
3479 ArgDecl -> IDENTIFIER : FormalType ${ {
3480 struct variable *v = var_decl(c, $ID.txt);
3481 $0 = new_pos(var, $ID);
3488 ##### Function calls
3490 A function call can appear either as an expression or as a statement.
3491 We use a new 'Funcall' binode type to link the function with a list of
3492 arguments, form with the 'List' nodes.
3494 We have already seen the "Term" which is how a function call can appear
3495 in an expression. To parse a function call into a statement we include
3496 it in the "SimpleStatement Grammar" which will be described later.
3502 | Term ( ExpressionList ) ${ {
3503 struct binode *b = new(binode);
3506 b->right = reorder_bilist($<EL);
3510 struct binode *b = new(binode);
3517 ###### SimpleStatement Grammar
3519 | Term ( ExpressionList ) ${ {
3520 struct binode *b = new(binode);
3523 b->right = reorder_bilist($<EL);
3527 ###### print binode cases
3530 do_indent(indent, "");
3531 print_exec(b->left, -1, bracket);
3533 for (b = cast(binode, b->right); b; b = cast(binode, b->right)) {
3536 print_exec(b->left, -1, bracket);
3546 ###### propagate binode cases
3549 /* Every arg must match formal parameter, and result
3550 * is return type of function
3552 struct binode *args = cast(binode, b->right);
3553 struct var *v = cast(var, b->left);
3555 if (!v->var->type || v->var->type->check_args == NULL) {
3556 type_err(c, "error: attempt to call a non-function.",
3557 prog, NULL, 0, NULL);
3561 v->var->type->check_args(c, perr, v->var->type, args);
3562 if (v->var->type->function.inline_result)
3564 return v->var->type->function.return_type;
3567 ###### interp binode cases
3570 struct var *v = cast(var, b->left);
3571 struct type *t = v->var->type;
3572 void *oldlocal = c->local;
3573 int old_size = c->local_size;
3574 void *local = calloc(1, t->function.local_size);
3575 struct value *fbody = var_value(c, v->var);
3576 struct binode *arg = cast(binode, b->right);
3577 struct binode *param = t->function.params;
3580 struct var *pv = cast(var, param->left);
3581 struct type *vtype = NULL;
3582 struct value val = interp_exec(c, arg->left, &vtype);
3584 c->local = local; c->local_size = t->function.local_size;
3585 lval = var_value(c, pv->var);
3586 c->local = oldlocal; c->local_size = old_size;
3587 memcpy(lval, &val, vtype->size);
3588 param = cast(binode, param->right);
3589 arg = cast(binode, arg->right);
3591 c->local = local; c->local_size = t->function.local_size;
3592 if (t->function.inline_result && dtype) {
3593 _interp_exec(c, fbody->function, NULL, NULL);
3594 memcpy(dest, local, dtype->size);
3595 rvtype = ret.type = NULL;
3597 rv = interp_exec(c, fbody->function, &rvtype);
3598 c->local = oldlocal; c->local_size = old_size;
3603 ## Complex executables: statements and expressions
3605 Now that we have types and values and variables and most of the basic
3606 Terms which provide access to these, we can explore the more complex
3607 code that combine all of these to get useful work done. Specifically
3608 statements and expressions.
3610 Expressions are various combinations of Terms. We will use operator
3611 precedence to ensure correct parsing. The simplest Expression is just a
3612 Term - others will follow.
3617 Expression -> Term ${ $0 = $<Term; }$
3618 ## expression grammar
3620 ### Expressions: Conditional
3622 Our first user of the `binode` will be conditional expressions, which
3623 is a bit odd as they actually have three components. That will be
3624 handled by having 2 binodes for each expression. The conditional
3625 expression is the lowest precedence operator which is why we define it
3626 first - to start the precedence list.
3628 Conditional expressions are of the form "value `if` condition `else`
3629 other_value". They associate to the right, so everything to the right
3630 of `else` is part of an else value, while only a higher-precedence to
3631 the left of `if` is the if values. Between `if` and `else` there is no
3632 room for ambiguity, so a full conditional expression is allowed in
3638 ###### declare terminals
3642 ###### expression grammar
3644 | Expression if Expression else Expression $$ifelse ${ {
3645 struct binode *b1 = new(binode);
3646 struct binode *b2 = new(binode);
3656 ###### print binode cases
3659 b2 = cast(binode, b->right);
3660 if (bracket) printf("(");
3661 print_exec(b2->left, -1, bracket);
3663 print_exec(b->left, -1, bracket);
3665 print_exec(b2->right, -1, bracket);
3666 if (bracket) printf(")");
3669 ###### propagate binode cases
3672 /* cond must be Tbool, others must match */
3673 struct binode *b2 = cast(binode, b->right);
3676 propagate_types(b->left, c, perr, Tbool, 0);
3677 t = propagate_types(b2->left, c, perr, type, Rnolabel);
3678 t2 = propagate_types(b2->right, c, perr, type ?: t, Rnolabel);
3682 ###### interp binode cases
3685 struct binode *b2 = cast(binode, b->right);
3686 left = interp_exec(c, b->left, <ype);
3688 rv = interp_exec(c, b2->left, &rvtype); // UNTESTED
3690 rv = interp_exec(c, b2->right, &rvtype);
3696 We take a brief detour, now that we have expressions, to describe lists
3697 of expressions. These will be needed for function parameters and
3698 possibly other situations. They seem generic enough to introduce here
3699 to be used elsewhere.
3701 And ExpressionList will use the `List` type of `binode`, building up at
3702 the end. And place where they are used will probably call
3703 `reorder_bilist()` to get a more normal first/next arrangement.
3705 ###### declare terminals
3708 `List` execs have no implicit semantics, so they are never propagated or
3709 interpreted. The can be printed as a comma separate list, which is how
3710 they are parsed. Note they are also used for function formal parameter
3711 lists. In that case a separate function is used to print them.
3713 ###### print binode cases
3717 print_exec(b->left, -1, bracket);
3720 b = cast(binode, b->right);
3724 ###### propagate binode cases
3725 case List: abort(); // NOTEST
3726 ###### interp binode cases
3727 case List: abort(); // NOTEST
3732 ExpressionList -> ExpressionList , Expression ${
3745 ### Expressions: Boolean
3747 The next class of expressions to use the `binode` will be Boolean
3748 expressions. "`and then`" and "`or else`" are similar to `and` and `or`
3749 have same corresponding precendence. The difference is that they don't
3750 evaluate the second expression if not necessary.
3759 ###### declare terminals
3764 ###### expression grammar
3765 | Expression or Expression ${ {
3766 struct binode *b = new(binode);
3772 | Expression or else Expression ${ {
3773 struct binode *b = new(binode);
3780 | Expression and Expression ${ {
3781 struct binode *b = new(binode);
3787 | Expression and then Expression ${ {
3788 struct binode *b = new(binode);
3795 | not Expression ${ {
3796 struct binode *b = new(binode);
3802 ###### print binode cases
3804 if (bracket) printf("(");
3805 print_exec(b->left, -1, bracket);
3807 print_exec(b->right, -1, bracket);
3808 if (bracket) printf(")");
3811 if (bracket) printf("(");
3812 print_exec(b->left, -1, bracket);
3813 printf(" and then ");
3814 print_exec(b->right, -1, bracket);
3815 if (bracket) printf(")");
3818 if (bracket) printf("(");
3819 print_exec(b->left, -1, bracket);
3821 print_exec(b->right, -1, bracket);
3822 if (bracket) printf(")");
3825 if (bracket) printf("(");
3826 print_exec(b->left, -1, bracket);
3827 printf(" or else ");
3828 print_exec(b->right, -1, bracket);
3829 if (bracket) printf(")");
3832 if (bracket) printf("(");
3834 print_exec(b->right, -1, bracket);
3835 if (bracket) printf(")");
3838 ###### propagate binode cases
3844 /* both must be Tbool, result is Tbool */
3845 propagate_types(b->left, c, perr, Tbool, 0);
3846 propagate_types(b->right, c, perr, Tbool, 0);
3847 if (type && type != Tbool)
3848 type_err(c, "error: %1 operation found where %2 expected", prog,
3852 ###### interp binode cases
3854 rv = interp_exec(c, b->left, &rvtype);
3855 right = interp_exec(c, b->right, &rtype);
3856 rv.bool = rv.bool && right.bool;
3859 rv = interp_exec(c, b->left, &rvtype);
3861 rv = interp_exec(c, b->right, NULL);
3864 rv = interp_exec(c, b->left, &rvtype);
3865 right = interp_exec(c, b->right, &rtype);
3866 rv.bool = rv.bool || right.bool;
3869 rv = interp_exec(c, b->left, &rvtype);
3871 rv = interp_exec(c, b->right, NULL);
3874 rv = interp_exec(c, b->right, &rvtype);
3878 ### Expressions: Comparison
3880 Of slightly higher precedence that Boolean expressions are Comparisons.
3881 A comparison takes arguments of any comparable type, but the two types
3884 To simplify the parsing we introduce an `eop` which can record an
3885 expression operator, and the `CMPop` non-terminal will match one of them.
3892 ###### ast functions
3893 static void free_eop(struct eop *e)
3907 ###### declare terminals
3908 $LEFT < > <= >= == != CMPop
3910 ###### expression grammar
3911 | Expression CMPop Expression ${ {
3912 struct binode *b = new(binode);
3922 CMPop -> < ${ $0.op = Less; }$
3923 | > ${ $0.op = Gtr; }$
3924 | <= ${ $0.op = LessEq; }$
3925 | >= ${ $0.op = GtrEq; }$
3926 | == ${ $0.op = Eql; }$
3927 | != ${ $0.op = NEql; }$
3929 ###### print binode cases
3937 if (bracket) printf("(");
3938 print_exec(b->left, -1, bracket);
3940 case Less: printf(" < "); break;
3941 case LessEq: printf(" <= "); break;
3942 case Gtr: printf(" > "); break;
3943 case GtrEq: printf(" >= "); break;
3944 case Eql: printf(" == "); break;
3945 case NEql: printf(" != "); break;
3946 default: abort(); // NOTEST
3948 print_exec(b->right, -1, bracket);
3949 if (bracket) printf(")");
3952 ###### propagate binode cases
3959 /* Both must match but not be labels, result is Tbool */
3960 t = propagate_types(b->left, c, perr, NULL, Rnolabel);
3962 propagate_types(b->right, c, perr, t, 0);
3964 t = propagate_types(b->right, c, perr, NULL, Rnolabel); // UNTESTED
3966 t = propagate_types(b->left, c, perr, t, 0); // UNTESTED
3968 if (!type_compat(type, Tbool, 0))
3969 type_err(c, "error: Comparison returns %1 but %2 expected", prog,
3970 Tbool, rules, type);
3973 ###### interp binode cases
3982 left = interp_exec(c, b->left, <ype);
3983 right = interp_exec(c, b->right, &rtype);
3984 cmp = value_cmp(ltype, rtype, &left, &right);
3987 case Less: rv.bool = cmp < 0; break;
3988 case LessEq: rv.bool = cmp <= 0; break;
3989 case Gtr: rv.bool = cmp > 0; break;
3990 case GtrEq: rv.bool = cmp >= 0; break;
3991 case Eql: rv.bool = cmp == 0; break;
3992 case NEql: rv.bool = cmp != 0; break;
3993 default: rv.bool = 0; break; // NOTEST
3998 ### Expressions: Arithmetic etc.
4000 The remaining expressions with the highest precedence are arithmetic,
4001 string concatenation, string conversion, and testing. String concatenation
4002 (`++`) has the same precedence as multiplication and division, but lower
4005 Testing comes in two forms. A single question mark (`?`) is a uniary
4006 operator which converts come types into Boolean. The general meaning is
4007 "is this a value value" and there will be more uses as the language
4008 develops. A double questionmark (`??`) is a binary operator (Choose),
4009 with same precedence as multiplication, which returns the LHS if it
4010 tests successfully, else returns the RHS.
4012 String conversion is a temporary feature until I get a better type
4013 system. `$` is a prefix operator which expects a string and returns
4016 `+` and `-` are both infix and prefix operations (where they are
4017 absolute value and negation). These have different operator names.
4019 We also have a 'Bracket' operator which records where parentheses were
4020 found. This makes it easy to reproduce these when printing. Possibly I
4021 should only insert brackets were needed for precedence. Putting
4022 parentheses around an expression converts it into a Term,
4028 Absolute, Negate, Test,
4032 ###### declare terminals
4034 $LEFT * / % ++ ?? Top
4038 ###### expression grammar
4039 | Expression Eop Expression ${ {
4040 struct binode *b = new(binode);
4047 | Expression Top Expression ${ {
4048 struct binode *b = new(binode);
4055 | Uop Expression ${ {
4056 struct binode *b = new(binode);
4064 | ( Expression ) ${ {
4065 struct binode *b = new_pos(binode, $1);
4074 Eop -> + ${ $0.op = Plus; }$
4075 | - ${ $0.op = Minus; }$
4077 Uop -> + ${ $0.op = Absolute; }$
4078 | - ${ $0.op = Negate; }$
4079 | $ ${ $0.op = StringConv; }$
4080 | ? ${ $0.op = Test; }$
4082 Top -> * ${ $0.op = Times; }$
4083 | / ${ $0.op = Divide; }$
4084 | % ${ $0.op = Rem; }$
4085 | ++ ${ $0.op = Concat; }$
4086 | ?? ${ $0.op = Choose; }$
4088 ###### print binode cases
4096 if (bracket) printf("(");
4097 print_exec(b->left, indent, bracket);
4099 case Plus: fputs(" + ", stdout); break;
4100 case Minus: fputs(" - ", stdout); break;
4101 case Times: fputs(" * ", stdout); break;
4102 case Divide: fputs(" / ", stdout); break;
4103 case Rem: fputs(" % ", stdout); break;
4104 case Concat: fputs(" ++ ", stdout); break;
4105 case Choose: fputs(" ?? ", stdout); break;
4106 default: abort(); // NOTEST
4108 print_exec(b->right, indent, bracket);
4109 if (bracket) printf(")");
4115 if (bracket) printf("(");
4117 case Absolute: fputs("+", stdout); break;
4118 case Negate: fputs("-", stdout); break;
4119 case StringConv: fputs("$", stdout); break;
4120 case Test: fputs("?", stdout); break;
4121 default: abort(); // NOTEST
4123 print_exec(b->right, indent, bracket);
4124 if (bracket) printf(")");
4128 print_exec(b->right, indent, bracket);
4132 ###### propagate binode cases
4138 /* both must be numbers, result is Tnum */
4141 /* as propagate_types ignores a NULL,
4142 * unary ops fit here too */
4143 propagate_types(b->left, c, perr, Tnum, 0);
4144 propagate_types(b->right, c, perr, Tnum, 0);
4145 if (!type_compat(type, Tnum, 0))
4146 type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
4151 /* both must be Tstr, result is Tstr */
4152 propagate_types(b->left, c, perr, Tstr, 0);
4153 propagate_types(b->right, c, perr, Tstr, 0);
4154 if (!type_compat(type, Tstr, 0))
4155 type_err(c, "error: Concat returns %1 but %2 expected", prog,
4160 /* op must be string, result is number */
4161 propagate_types(b->left, c, perr, Tstr, 0);
4162 if (!type_compat(type, Tnum, 0))
4163 type_err(c, // UNTESTED
4164 "error: Can only convert string to number, not %1",
4165 prog, type, 0, NULL);
4169 /* LHS must support ->test, result is Tbool */
4170 t = propagate_types(b->right, c, perr, NULL, 0);
4172 type_err(c, "error: '?' requires a testable value, not %1",
4177 /* LHS and RHS must match and are returned. Must support
4180 t = propagate_types(b->left, c, perr, type, rules);
4181 t = propagate_types(b->right, c, perr, t, rules);
4182 if (t && t->test == NULL)
4183 type_err(c, "error: \"??\" requires a testable value, not %1",
4188 return propagate_types(b->right, c, perr, type, 0);
4190 ###### interp binode cases
4193 rv = interp_exec(c, b->left, &rvtype);
4194 right = interp_exec(c, b->right, &rtype);
4195 mpq_add(rv.num, rv.num, right.num);
4198 rv = interp_exec(c, b->left, &rvtype);
4199 right = interp_exec(c, b->right, &rtype);
4200 mpq_sub(rv.num, rv.num, right.num);
4203 rv = interp_exec(c, b->left, &rvtype);
4204 right = interp_exec(c, b->right, &rtype);
4205 mpq_mul(rv.num, rv.num, right.num);
4208 rv = interp_exec(c, b->left, &rvtype);
4209 right = interp_exec(c, b->right, &rtype);
4210 mpq_div(rv.num, rv.num, right.num);
4215 left = interp_exec(c, b->left, <ype);
4216 right = interp_exec(c, b->right, &rtype);
4217 mpz_init(l); mpz_init(r); mpz_init(rem);
4218 mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
4219 mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
4220 mpz_tdiv_r(rem, l, r);
4221 val_init(Tnum, &rv);
4222 mpq_set_z(rv.num, rem);
4223 mpz_clear(r); mpz_clear(l); mpz_clear(rem);
4228 rv = interp_exec(c, b->right, &rvtype);
4229 mpq_neg(rv.num, rv.num);
4232 rv = interp_exec(c, b->right, &rvtype);
4233 mpq_abs(rv.num, rv.num);
4236 rv = interp_exec(c, b->right, &rvtype);
4239 left = interp_exec(c, b->left, <ype);
4240 right = interp_exec(c, b->right, &rtype);
4242 rv.str = text_join(left.str, right.str);
4245 right = interp_exec(c, b->right, &rvtype);
4249 struct text tx = right.str;
4252 if (tx.txt[0] == '-') {
4253 neg = 1; // UNTESTED
4254 tx.txt++; // UNTESTED
4255 tx.len--; // UNTESTED
4257 if (number_parse(rv.num, tail, tx) == 0)
4258 mpq_init(rv.num); // UNTESTED
4260 mpq_neg(rv.num, rv.num); // UNTESTED
4262 printf("Unsupported suffix: %.*s\n", tx.len, tx.txt); // UNTESTED
4266 right = interp_exec(c, b->right, &rtype);
4268 rv.bool = !!rtype->test(rtype, &right);
4271 left = interp_exec(c, b->left, <ype);
4272 if (ltype->test(ltype, &left)) {
4277 rv = interp_exec(c, b->right, &rvtype);
4280 ###### value functions
4282 static struct text text_join(struct text a, struct text b)
4285 rv.len = a.len + b.len;
4286 rv.txt = malloc(rv.len);
4287 memcpy(rv.txt, a.txt, a.len);
4288 memcpy(rv.txt+a.len, b.txt, b.len);
4292 ### Blocks, Statements, and Statement lists.
4294 Now that we have expressions out of the way we need to turn to
4295 statements. There are simple statements and more complex statements.
4296 Simple statements do not contain (syntactic) newlines, complex statements do.
4298 Statements often come in sequences and we have corresponding simple
4299 statement lists and complex statement lists.
4300 The former comprise only simple statements separated by semicolons.
4301 The later comprise complex statements and simple statement lists. They are
4302 separated by newlines. Thus the semicolon is only used to separate
4303 simple statements on the one line. This may be overly restrictive,
4304 but I'm not sure I ever want a complex statement to share a line with
4307 Note that a simple statement list can still use multiple lines if
4308 subsequent lines are indented, so
4310 ###### Example: wrapped simple statement list
4315 is a single simple statement list. This might allow room for
4316 confusion, so I'm not set on it yet.
4318 A simple statement list needs no extra syntax. A complex statement
4319 list has two syntactic forms. It can be enclosed in braces (much like
4320 C blocks), or it can be introduced by an indent and continue until an
4321 unindented newline (much like Python blocks). With this extra syntax
4322 it is referred to as a block.
4324 Note that a block does not have to include any newlines if it only
4325 contains simple statements. So both of:
4327 if condition: a=b; d=f
4329 if condition { a=b; print f }
4333 In either case the list is constructed from a `binode` list with
4334 `Block` as the operator. When parsing the list it is most convenient
4335 to append to the end, so a list is a list and a statement. When using
4336 the list it is more convenient to consider a list to be a statement
4337 and a list. So we need a function to re-order a list.
4338 `reorder_bilist` serves this purpose.
4340 The only stand-alone statement we introduce at this stage is `pass`
4341 which does nothing and is represented as a `NULL` pointer in a `Block`
4342 list. Other stand-alone statements will follow once the infrastructure
4345 As many statements will use binodes, we declare a binode pointer 'b' in
4346 the common header for all reductions to use.
4348 ###### Parser: reduce
4359 Block -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4360 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4361 | SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
4362 | SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
4363 | IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
4365 OpenBlock -> OpenScope { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4366 | OpenScope { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4367 | OpenScope SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
4368 | OpenScope SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
4369 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
4371 UseBlock -> { OpenScope IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4372 | { OpenScope SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4373 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
4375 ColonBlock -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
4376 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
4377 | : SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
4378 | : SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
4379 | : IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
4381 Statementlist -> ComplexStatements ${ $0 = reorder_bilist($<CS); }$
4383 ComplexStatements -> ComplexStatements ComplexStatement ${
4393 | ComplexStatement ${
4405 ComplexStatement -> SimpleStatements Newlines ${
4406 $0 = reorder_bilist($<SS);
4408 | SimpleStatements ; Newlines ${
4409 $0 = reorder_bilist($<SS);
4411 ## ComplexStatement Grammar
4414 SimpleStatements -> SimpleStatements ; SimpleStatement ${
4420 | SimpleStatement ${
4429 SimpleStatement -> pass ${ $0 = NULL; }$
4430 | ERROR ${ tok_err(c, "Syntax error in statement", &$1); }$
4431 ## SimpleStatement Grammar
4433 ###### print binode cases
4437 if (b->left == NULL) // UNTESTED
4438 printf("pass"); // UNTESTED
4440 print_exec(b->left, indent, bracket); // UNTESTED
4441 if (b->right) { // UNTESTED
4442 printf("; "); // UNTESTED
4443 print_exec(b->right, indent, bracket); // UNTESTED
4446 // block, one per line
4447 if (b->left == NULL)
4448 do_indent(indent, "pass\n");
4450 print_exec(b->left, indent, bracket);
4452 print_exec(b->right, indent, bracket);
4456 ###### propagate binode cases
4459 /* If any statement returns something other than Tnone
4460 * or Tbool then all such must return same type.
4461 * As each statement may be Tnone or something else,
4462 * we must always pass NULL (unknown) down, otherwise an incorrect
4463 * error might occur. We never return Tnone unless it is
4468 for (e = b; e; e = cast(binode, e->right)) {
4469 t = propagate_types(e->left, c, perr, NULL, rules);
4470 if ((rules & Rboolok) && (t == Tbool || t == Tnone))
4472 if (t == Tnone && e->right)
4473 /* Only the final statement *must* return a value
4481 type_err(c, "error: expected %1%r, found %2",
4482 e->left, type, rules, t);
4488 ###### interp binode cases
4490 while (rvtype == Tnone &&
4493 rv = interp_exec(c, b->left, &rvtype);
4494 b = cast(binode, b->right);
4498 ### The Print statement
4500 `print` is a simple statement that takes a comma-separated list of
4501 expressions and prints the values separated by spaces and terminated
4502 by a newline. No control of formatting is possible.
4504 `print` uses `ExpressionList` to collect the expressions and stores them
4505 on the left side of a `Print` binode unlessthere is a trailing comma
4506 when the list is stored on the `right` side and no trailing newline is
4512 ##### declare terminals
4515 ###### SimpleStatement Grammar
4517 | print ExpressionList ${
4518 $0 = b = new_pos(binode, $1);
4521 b->left = reorder_bilist($<EL);
4523 | print ExpressionList , ${ {
4524 $0 = b = new_pos(binode, $1);
4526 b->right = reorder_bilist($<EL);
4530 $0 = b = new_pos(binode, $1);
4536 ###### print binode cases
4539 do_indent(indent, "print");
4541 print_exec(b->right, -1, bracket);
4544 print_exec(b->left, -1, bracket);
4549 ###### propagate binode cases
4552 /* don't care but all must be consistent */
4554 b = cast(binode, b->left);
4556 b = cast(binode, b->right);
4558 propagate_types(b->left, c, perr, NULL, Rnolabel);
4559 b = cast(binode, b->right);
4563 ###### interp binode cases
4567 struct binode *b2 = cast(binode, b->left);
4569 b2 = cast(binode, b->right);
4570 for (; b2; b2 = cast(binode, b2->right)) {
4571 left = interp_exec(c, b2->left, <ype);
4572 print_value(ltype, &left, stdout);
4573 free_value(ltype, &left);
4577 if (b->right == NULL)
4583 ###### Assignment statement
4585 An assignment will assign a value to a variable, providing it hasn't
4586 been declared as a constant. The analysis phase ensures that the type
4587 will be correct so the interpreter just needs to perform the
4588 calculation. There is a form of assignment which declares a new
4589 variable as well as assigning a value. If a name is assigned before
4590 it is declared, and error will be raised as the name is created as
4591 `Tlabel` and it is illegal to assign to such names.
4597 ###### declare terminals
4600 ###### SimpleStatement Grammar
4601 | Term = Expression ${
4602 $0 = b= new(binode);
4607 | VariableDecl = Expression ${
4608 $0 = b= new(binode);
4615 if ($1->var->where_set == NULL) {
4617 "Variable declared with no type or value: %v",
4621 $0 = b = new(binode);
4628 ###### print binode cases
4631 do_indent(indent, "");
4632 print_exec(b->left, -1, bracket);
4634 print_exec(b->right, -1, bracket);
4641 struct variable *v = cast(var, b->left)->var;
4642 do_indent(indent, "");
4643 print_exec(b->left, -1, bracket);
4644 if (cast(var, b->left)->var->constant) {
4646 if (v->explicit_type) {
4647 type_print(v->type, stdout);
4652 if (v->explicit_type) {
4653 type_print(v->type, stdout);
4659 print_exec(b->right, -1, bracket);
4666 ###### propagate binode cases
4670 /* Both must match and not be labels,
4671 * Type must support 'dup',
4672 * For Assign, left must not be constant.
4675 t = propagate_types(b->left, c, perr, NULL,
4676 Rnolabel | (b->op == Assign ? Rnoconstant : 0));
4681 if (propagate_types(b->right, c, perr, t, 0) != t)
4682 if (b->left->type == Xvar)
4683 type_err(c, "info: variable '%v' was set as %1 here.",
4684 cast(var, b->left)->var->where_set, t, rules, NULL);
4686 t = propagate_types(b->right, c, perr, NULL, Rnolabel);
4688 propagate_types(b->left, c, perr, t,
4689 (b->op == Assign ? Rnoconstant : 0));
4691 if (t && t->dup == NULL && !(*perr & Emaycopy))
4692 type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
4697 ###### interp binode cases
4700 lleft = linterp_exec(c, b->left, <ype);
4702 dinterp_exec(c, b->right, lleft, ltype, 1);
4708 struct variable *v = cast(var, b->left)->var;
4711 val = var_value(c, v);
4712 if (v->type->prepare_type)
4713 v->type->prepare_type(c, v->type, 0);
4715 dinterp_exec(c, b->right, val, v->type, 0);
4717 val_init(v->type, val);
4721 ### The `use` statement
4723 The `use` statement is the last "simple" statement. It is needed when a
4724 statement block can return a value. This includes the body of a
4725 function which has a return type, and the "condition" code blocks in
4726 `if`, `while`, and `switch` statements.
4731 ###### declare terminals
4734 ###### SimpleStatement Grammar
4736 $0 = b = new_pos(binode, $1);
4739 if (b->right->type == Xvar) {
4740 struct var *v = cast(var, b->right);
4741 if (v->var->type == Tnone) {
4742 /* Convert this to a label */
4745 v->var->type = Tlabel;
4746 val = global_alloc(c, Tlabel, v->var, NULL);
4752 ###### print binode cases
4755 do_indent(indent, "use ");
4756 print_exec(b->right, -1, bracket);
4761 ###### propagate binode cases
4764 /* result matches value */
4765 return propagate_types(b->right, c, perr, type, 0);
4767 ###### interp binode cases
4770 rv = interp_exec(c, b->right, &rvtype);
4773 ### The Conditional Statement
4775 This is the biggy and currently the only complex statement. This
4776 subsumes `if`, `while`, `do/while`, `switch`, and some parts of `for`.
4777 It is comprised of a number of parts, all of which are optional though
4778 set combinations apply. Each part is (usually) a key word (`then` is
4779 sometimes optional) followed by either an expression or a code block,
4780 except the `casepart` which is a "key word and an expression" followed
4781 by a code block. The code-block option is valid for all parts and,
4782 where an expression is also allowed, the code block can use the `use`
4783 statement to report a value. If the code block does not report a value
4784 the effect is similar to reporting `True`.
4786 The `else` and `case` parts, as well as `then` when combined with
4787 `if`, can contain a `use` statement which will apply to some
4788 containing conditional statement. `for` parts, `do` parts and `then`
4789 parts used with `for` can never contain a `use`, except in some
4790 subordinate conditional statement.
4792 If there is a `forpart`, it is executed first, only once.
4793 If there is a `dopart`, then it is executed repeatedly providing
4794 always that the `condpart` or `cond`, if present, does not return a non-True
4795 value. `condpart` can fail to return any value if it simply executes
4796 to completion. This is treated the same as returning `True`.
4798 If there is a `thenpart` it will be executed whenever the `condpart`
4799 or `cond` returns True (or does not return any value), but this will happen
4800 *after* `dopart` (when present).
4802 If `elsepart` is present it will be executed at most once when the
4803 condition returns `False` or some value that isn't `True` and isn't
4804 matched by any `casepart`. If there are any `casepart`s, they will be
4805 executed when the condition returns a matching value.
4807 The particular sorts of values allowed in case parts has not yet been
4808 determined in the language design, so nothing is prohibited.
4810 The various blocks in this complex statement potentially provide scope
4811 for variables as described earlier. Each such block must include the
4812 "OpenScope" nonterminal before parsing the block, and must call
4813 `var_block_close()` when closing the block.
4815 The code following "`if`", "`switch`" and "`for`" does not get its own
4816 scope, but is in a scope covering the whole statement, so names
4817 declared there cannot be redeclared elsewhere. Similarly the
4818 condition following "`while`" is in a scope the covers the body
4819 ("`do`" part) of the loop, and which does not allow conditional scope
4820 extension. Code following "`then`" (both looping and non-looping),
4821 "`else`" and "`case`" each get their own local scope.
4823 The type requirements on the code block in a `whilepart` are quite
4824 unusal. It is allowed to return a value of some identifiable type, in
4825 which case the loop aborts and an appropriate `casepart` is run, or it
4826 can return a Boolean, in which case the loop either continues to the
4827 `dopart` (on `True`) or aborts and runs the `elsepart` (on `False`).
4828 This is different both from the `ifpart` code block which is expected to
4829 return a Boolean, or the `switchpart` code block which is expected to
4830 return the same type as the casepart values. The correct analysis of
4831 the type of the `whilepart` code block is the reason for the
4832 `Rboolok` flag which is passed to `propagate_types()`.
4834 The `cond_statement` cannot fit into a `binode` so a new `exec` is
4835 defined. As there are two scopes which cover multiple parts - one for
4836 the whole statement and one for "while" and "do" - and as we will use
4837 the 'struct exec' to track scopes, we actually need two new types of
4838 exec. One is a `binode` for the looping part, the rest is the
4839 `cond_statement`. The `cond_statement` will use an auxilliary `struct
4840 casepart` to track a list of case parts.
4851 struct exec *action;
4852 struct casepart *next;
4854 struct cond_statement {
4856 struct exec *forpart, *condpart, *thenpart, *elsepart;
4857 struct binode *looppart;
4858 struct casepart *casepart;
4861 ###### ast functions
4863 static void free_casepart(struct casepart *cp)
4867 free_exec(cp->value);
4868 free_exec(cp->action);
4875 static void free_cond_statement(struct cond_statement *s)
4879 free_exec(s->forpart);
4880 free_exec(s->condpart);
4881 free_exec(s->looppart);
4882 free_exec(s->thenpart);
4883 free_exec(s->elsepart);
4884 free_casepart(s->casepart);
4888 ###### free exec cases
4889 case Xcond_statement: free_cond_statement(cast(cond_statement, e)); break;
4891 ###### ComplexStatement Grammar
4892 | CondStatement ${ $0 = $<1; }$
4894 ###### declare terminals
4895 $TERM for then while do
4902 // A CondStatement must end with EOL, as does CondSuffix and
4904 // ForPart, ThenPart, SwitchPart, CasePart are non-empty and
4905 // may or may not end with EOL
4906 // WhilePart and IfPart include an appropriate Suffix
4908 // ForPart, SwitchPart, and IfPart open scopes, o we have to close
4909 // them. WhilePart opens and closes its own scope.
4910 CondStatement -> ForPart OptNL ThenPart OptNL WhilePart CondSuffix ${
4913 $0->thenpart = $<TP;
4914 $0->looppart = $<WP;
4915 var_block_close(c, CloseSequential, $0);
4917 | ForPart OptNL WhilePart CondSuffix ${
4920 $0->looppart = $<WP;
4921 var_block_close(c, CloseSequential, $0);
4923 | WhilePart CondSuffix ${
4925 $0->looppart = $<WP;
4927 | SwitchPart OptNL CasePart CondSuffix ${
4929 $0->condpart = $<SP;
4930 $CP->next = $0->casepart;
4931 $0->casepart = $<CP;
4932 var_block_close(c, CloseSequential, $0);
4934 | SwitchPart : IN OptNL CasePart CondSuffix OUT Newlines ${
4936 $0->condpart = $<SP;
4937 $CP->next = $0->casepart;
4938 $0->casepart = $<CP;
4939 var_block_close(c, CloseSequential, $0);
4941 | IfPart IfSuffix ${
4943 $0->condpart = $IP.condpart; $IP.condpart = NULL;
4944 $0->thenpart = $IP.thenpart; $IP.thenpart = NULL;
4945 // This is where we close an "if" statement
4946 var_block_close(c, CloseSequential, $0);
4949 CondSuffix -> IfSuffix ${
4952 | Newlines CasePart CondSuffix ${
4954 $CP->next = $0->casepart;
4955 $0->casepart = $<CP;
4957 | CasePart CondSuffix ${
4959 $CP->next = $0->casepart;
4960 $0->casepart = $<CP;
4963 IfSuffix -> Newlines ${ $0 = new(cond_statement); }$
4964 | Newlines ElsePart ${ $0 = $<EP; }$
4965 | ElsePart ${$0 = $<EP; }$
4967 ElsePart -> else OpenBlock Newlines ${
4968 $0 = new(cond_statement);
4969 $0->elsepart = $<OB;
4970 var_block_close(c, CloseElse, $0->elsepart);
4972 | else OpenScope CondStatement ${
4973 $0 = new(cond_statement);
4974 $0->elsepart = $<CS;
4975 var_block_close(c, CloseElse, $0->elsepart);
4979 CasePart -> case Expression OpenScope ColonBlock ${
4980 $0 = calloc(1,sizeof(struct casepart));
4983 var_block_close(c, CloseParallel, $0->action);
4987 // These scopes are closed in CondStatement
4988 ForPart -> for OpenBlock ${
4992 ThenPart -> then OpenBlock ${
4994 var_block_close(c, CloseSequential, $0);
4998 // This scope is closed in CondStatement
4999 WhilePart -> while UseBlock OptNL do OpenBlock ${
5004 var_block_close(c, CloseSequential, $0->right);
5005 var_block_close(c, CloseSequential, $0);
5007 | while OpenScope Expression OpenScope ColonBlock ${
5012 var_block_close(c, CloseSequential, $0->right);
5013 var_block_close(c, CloseSequential, $0);
5017 IfPart -> if UseBlock OptNL then OpenBlock ${
5020 var_block_close(c, CloseParallel, $0.thenpart);
5022 | if OpenScope Expression OpenScope ColonBlock ${
5025 var_block_close(c, CloseParallel, $0.thenpart);
5027 | if OpenScope Expression OpenScope OptNL then Block ${
5030 var_block_close(c, CloseParallel, $0.thenpart);
5034 // This scope is closed in CondStatement
5035 SwitchPart -> switch OpenScope Expression ${
5038 | switch UseBlock ${
5042 ###### print binode cases
5044 if (b->left && b->left->type == Xbinode &&
5045 cast(binode, b->left)->op == Block) {
5047 do_indent(indent, "while {\n");
5049 do_indent(indent, "while\n");
5050 print_exec(b->left, indent+1, bracket);
5052 do_indent(indent, "} do {\n");
5054 do_indent(indent, "do\n");
5055 print_exec(b->right, indent+1, bracket);
5057 do_indent(indent, "}\n");
5059 do_indent(indent, "while ");
5060 print_exec(b->left, 0, bracket);
5065 print_exec(b->right, indent+1, bracket);
5067 do_indent(indent, "}\n");
5071 ###### print exec cases
5073 case Xcond_statement:
5075 struct cond_statement *cs = cast(cond_statement, e);
5076 struct casepart *cp;
5078 do_indent(indent, "for");
5079 if (bracket) printf(" {\n"); else printf("\n");
5080 print_exec(cs->forpart, indent+1, bracket);
5083 do_indent(indent, "} then {\n");
5085 do_indent(indent, "then\n");
5086 print_exec(cs->thenpart, indent+1, bracket);
5088 if (bracket) do_indent(indent, "}\n");
5091 print_exec(cs->looppart, indent, bracket);
5095 do_indent(indent, "switch");
5097 do_indent(indent, "if");
5098 if (cs->condpart && cs->condpart->type == Xbinode &&
5099 cast(binode, cs->condpart)->op == Block) {
5104 print_exec(cs->condpart, indent+1, bracket);
5106 do_indent(indent, "}\n");
5108 do_indent(indent, "then\n");
5109 print_exec(cs->thenpart, indent+1, bracket);
5113 print_exec(cs->condpart, 0, bracket);
5119 print_exec(cs->thenpart, indent+1, bracket);
5121 do_indent(indent, "}\n");
5126 for (cp = cs->casepart; cp; cp = cp->next) {
5127 do_indent(indent, "case ");
5128 print_exec(cp->value, -1, 0);
5133 print_exec(cp->action, indent+1, bracket);
5135 do_indent(indent, "}\n");
5138 do_indent(indent, "else");
5143 print_exec(cs->elsepart, indent+1, bracket);
5145 do_indent(indent, "}\n");
5150 ###### propagate binode cases
5152 t = propagate_types(b->right, c, perr, Tnone, 0);
5153 if (!type_compat(Tnone, t, 0))
5154 *perr |= Efail; // UNTESTED
5155 return propagate_types(b->left, c, perr, type, rules);
5157 ###### propagate exec cases
5158 case Xcond_statement:
5160 // forpart and looppart->right must return Tnone
5161 // thenpart must return Tnone if there is a loopart,
5162 // otherwise it is like elsepart.
5164 // be bool if there is no casepart
5165 // match casepart->values if there is a switchpart
5166 // either be bool or match casepart->value if there
5168 // elsepart and casepart->action must match the return type
5169 // expected of this statement.
5170 struct cond_statement *cs = cast(cond_statement, prog);
5171 struct casepart *cp;
5173 t = propagate_types(cs->forpart, c, perr, Tnone, 0);
5174 if (!type_compat(Tnone, t, 0))
5175 *perr |= Efail; // UNTESTED
5178 t = propagate_types(cs->thenpart, c, perr, Tnone, 0);
5179 if (!type_compat(Tnone, t, 0))
5180 *perr |= Efail; // UNTESTED
5182 if (cs->casepart == NULL) {
5183 propagate_types(cs->condpart, c, perr, Tbool, 0);
5184 propagate_types(cs->looppart, c, perr, Tbool, 0);
5186 /* Condpart must match case values, with bool permitted */
5188 for (cp = cs->casepart;
5189 cp && !t; cp = cp->next)
5190 t = propagate_types(cp->value, c, perr, NULL, 0);
5191 if (!t && cs->condpart)
5192 t = propagate_types(cs->condpart, c, perr, NULL, Rboolok); // UNTESTED
5193 if (!t && cs->looppart)
5194 t = propagate_types(cs->looppart, c, perr, NULL, Rboolok); // UNTESTED
5195 // Now we have a type (I hope) push it down
5197 for (cp = cs->casepart; cp; cp = cp->next)
5198 propagate_types(cp->value, c, perr, t, 0);
5199 propagate_types(cs->condpart, c, perr, t, Rboolok);
5200 propagate_types(cs->looppart, c, perr, t, Rboolok);
5203 // (if)then, else, and case parts must return expected type.
5204 if (!cs->looppart && !type)
5205 type = propagate_types(cs->thenpart, c, perr, NULL, rules);
5207 type = propagate_types(cs->elsepart, c, perr, NULL, rules);
5208 for (cp = cs->casepart;
5210 cp = cp->next) // UNTESTED
5211 type = propagate_types(cp->action, c, perr, NULL, rules); // UNTESTED
5214 propagate_types(cs->thenpart, c, perr, type, rules);
5215 propagate_types(cs->elsepart, c, perr, type, rules);
5216 for (cp = cs->casepart; cp ; cp = cp->next)
5217 propagate_types(cp->action, c, perr, type, rules);
5223 ###### interp binode cases
5225 // This just performs one iterration of the loop
5226 rv = interp_exec(c, b->left, &rvtype);
5227 if (rvtype == Tnone ||
5228 (rvtype == Tbool && rv.bool != 0))
5229 // rvtype is Tnone or Tbool, doesn't need to be freed
5230 interp_exec(c, b->right, NULL);
5233 ###### interp exec cases
5234 case Xcond_statement:
5236 struct value v, cnd;
5237 struct type *vtype, *cndtype;
5238 struct casepart *cp;
5239 struct cond_statement *cs = cast(cond_statement, e);
5242 interp_exec(c, cs->forpart, NULL);
5244 while ((cnd = interp_exec(c, cs->looppart, &cndtype)),
5245 cndtype == Tnone || (cndtype == Tbool && cnd.bool != 0))
5246 interp_exec(c, cs->thenpart, NULL);
5248 cnd = interp_exec(c, cs->condpart, &cndtype);
5249 if ((cndtype == Tnone ||
5250 (cndtype == Tbool && cnd.bool != 0))) {
5251 // cnd is Tnone or Tbool, doesn't need to be freed
5252 rv = interp_exec(c, cs->thenpart, &rvtype);
5253 // skip else (and cases)
5257 for (cp = cs->casepart; cp; cp = cp->next) {
5258 v = interp_exec(c, cp->value, &vtype);
5259 if (value_cmp(cndtype, vtype, &v, &cnd) == 0) {
5260 free_value(vtype, &v);
5261 free_value(cndtype, &cnd);
5262 rv = interp_exec(c, cp->action, &rvtype);
5265 free_value(vtype, &v);
5267 free_value(cndtype, &cnd);
5269 rv = interp_exec(c, cs->elsepart, &rvtype);
5276 ### Top level structure
5278 All the language elements so far can be used in various places. Now
5279 it is time to clarify what those places are.
5281 At the top level of a file there will be a number of declarations.
5282 Many of the things that can be declared haven't been described yet,
5283 such as functions, procedures, imports, and probably more.
5284 For now there are two sorts of things that can appear at the top
5285 level. They are predefined constants, `struct` types, and the `main`
5286 function. While the syntax will allow the `main` function to appear
5287 multiple times, that will trigger an error if it is actually attempted.
5289 The various declarations do not return anything. They store the
5290 various declarations in the parse context.
5292 ###### Parser: grammar
5295 Ocean -> OptNL DeclarationList
5297 ## declare terminals
5305 DeclarationList -> Declaration
5306 | DeclarationList Declaration
5308 Declaration -> ERROR Newlines ${
5309 tok_err(c, // UNTESTED
5310 "error: unhandled parse error", &$1);
5316 ## top level grammar
5320 ### The `const` section
5322 As well as being defined in with the code that uses them, constants can
5323 be declared at the top level. These have full-file scope, so they are
5324 always `InScope`, even before(!) they have been declared. The value of
5325 a top level constant can be given as an expression, and this is
5326 evaluated after parsing and before execution.
5328 A function call can be used to evaluate a constant, but it will not have
5329 access to any program state, once such statement becomes meaningful.
5330 e.g. arguments and filesystem will not be visible.
5332 Constants are defined in a section that starts with the reserved word
5333 `const` and then has a block with a list of assignment statements.
5334 For syntactic consistency, these must use the double-colon syntax to
5335 make it clear that they are constants. Type can also be given: if
5336 not, the type will be determined during analysis, as with other
5339 ###### parse context
5340 struct binode *constlist;
5342 ###### top level grammar
5346 DeclareConstant -> const { IN OptNL ConstList OUT OptNL } Newlines
5347 | const { SimpleConstList } Newlines
5348 | const IN OptNL ConstList OUT Newlines
5349 | const SimpleConstList Newlines
5351 ConstList -> ConstList SimpleConstLine
5354 SimpleConstList -> SimpleConstList ; Const
5358 SimpleConstLine -> SimpleConstList Newlines
5359 | ERROR Newlines ${ tok_err(c, "Syntax error in constant", &$1); }$
5362 CType -> Type ${ $0 = $<1; }$
5366 Const -> IDENTIFIER :: CType = Expression ${ {
5368 struct binode *bl, *bv;
5369 struct var *var = new_pos(var, $ID);
5371 v = var_decl(c, $ID.txt);
5373 v->where_decl = var;
5379 v = var_ref(c, $1.txt);
5380 if (v->type == Tnone) {
5381 v->where_decl = var;
5387 tok_err(c, "error: name already declared", &$1);
5388 type_err(c, "info: this is where '%v' was first declared",
5389 v->where_decl, NULL, 0, NULL);
5401 bl->left = c->constlist;
5406 ###### core functions
5407 static void resolve_consts(struct parse_context *c)
5411 enum { none, some, cannot } progress = none;
5413 c->constlist = reorder_bilist(c->constlist);
5416 for (b = cast(binode, c->constlist); b;
5417 b = cast(binode, b->right)) {
5419 struct binode *vb = cast(binode, b->left);
5420 struct var *v = cast(var, vb->left);
5421 if (v->var->frame_pos >= 0)
5425 propagate_types(vb->right, c, &perr,
5427 } while (perr & Eretry);
5429 c->parse_error += 1;
5430 else if (!(perr & Enoconst)) {
5432 struct value res = interp_exec(
5433 c, vb->right, &v->var->type);
5434 global_alloc(c, v->var->type, v->var, &res);
5436 if (progress == cannot)
5437 type_err(c, "error: const %v cannot be resolved.",
5447 progress = cannot; break;
5449 progress = none; break;
5454 ###### print const decls
5459 for (b = cast(binode, context.constlist); b;
5460 b = cast(binode, b->right)) {
5461 struct binode *vb = cast(binode, b->left);
5462 struct var *vr = cast(var, vb->left);
5463 struct variable *v = vr->var;
5469 printf(" %.*s :: ", v->name->name.len, v->name->name.txt);
5470 type_print(v->type, stdout);
5472 print_exec(vb->right, -1, 0);
5477 ###### free const decls
5478 free_binode(context.constlist);
5480 ### Function declarations
5482 The code in an Ocean program is all stored in function declarations.
5483 One of the functions must be named `main` and it must accept an array of
5484 strings as a parameter - the command line arguments.
5486 As this is the top level, several things are handled a bit differently.
5487 The function is not interpreted by `interp_exec` as that isn't passed
5488 the argument list which the program requires. Similarly type analysis
5489 is a bit more interesting at this level.
5491 ###### ast functions
5493 static struct type *handle_results(struct parse_context *c,
5494 struct binode *results)
5496 /* Create a 'struct' type from the results list, which
5497 * is a list for 'struct var'
5499 struct type *t = add_anon_type(c, &structure_prototype,
5504 for (b = results; b; b = cast(binode, b->right))
5506 t->structure.nfields = cnt;
5507 t->structure.fields = calloc(cnt, sizeof(struct field));
5509 for (b = results; b; b = cast(binode, b->right)) {
5510 struct var *v = cast(var, b->left);
5511 struct field *f = &t->structure.fields[cnt++];
5512 int a = v->var->type->align;
5513 f->name = v->var->name->name;
5514 f->type = v->var->type;
5516 f->offset = t->size;
5517 v->var->frame_pos = f->offset;
5518 t->size += ((f->type->size - 1) | (a-1)) + 1;
5521 variable_unlink_exec(v->var);
5523 free_binode(results);
5527 static struct variable *declare_function(struct parse_context *c,
5528 struct variable *name,
5529 struct binode *args,
5531 struct binode *results,
5535 struct value fn = {.function = code};
5537 var_block_close(c, CloseFunction, code);
5538 t = add_anon_type(c, &function_prototype,
5539 "func %.*s", name->name->name.len,
5540 name->name->name.txt);
5542 t->function.params = reorder_bilist(args);
5544 ret = handle_results(c, reorder_bilist(results));
5545 t->function.inline_result = 1;
5546 t->function.local_size = ret->size;
5548 t->function.return_type = ret;
5549 global_alloc(c, t, name, &fn);
5550 name->type->function.scope = c->out_scope;
5555 var_block_close(c, CloseFunction, NULL);
5557 c->out_scope = NULL;
5561 ###### declare terminals
5564 ###### top level grammar
5567 DeclareFunction -> func FuncName ( OpenScope ArgsLine ) Block Newlines ${
5568 $0 = declare_function(c, $<FN, $<Ar, Tnone, NULL, $<Bl);
5570 | func FuncName IN OpenScope Args OUT OptNL do Block Newlines ${
5571 $0 = declare_function(c, $<FN, $<Ar, Tnone, NULL, $<Bl);
5573 | func FuncName NEWLINE OpenScope OptNL do Block Newlines ${
5574 $0 = declare_function(c, $<FN, NULL, Tnone, NULL, $<Bl);
5576 | func FuncName ( OpenScope ArgsLine ) : Type Block Newlines ${
5577 $0 = declare_function(c, $<FN, $<Ar, $<Ty, NULL, $<Bl);
5579 | func FuncName ( OpenScope ArgsLine ) : ( ArgsLine ) Block Newlines ${
5580 $0 = declare_function(c, $<FN, $<AL, NULL, $<AL2, $<Bl);
5582 | func FuncName IN OpenScope Args OUT OptNL return Type Newlines do Block Newlines ${
5583 $0 = declare_function(c, $<FN, $<Ar, $<Ty, NULL, $<Bl);
5585 | func FuncName NEWLINE OpenScope return Type Newlines do Block Newlines ${
5586 $0 = declare_function(c, $<FN, NULL, $<Ty, NULL, $<Bl);
5588 | func FuncName IN OpenScope Args OUT OptNL return IN Args OUT OptNL do Block Newlines ${
5589 $0 = declare_function(c, $<FN, $<Ar, NULL, $<Ar2, $<Bl);
5591 | func FuncName NEWLINE OpenScope return IN Args OUT OptNL do Block Newlines ${
5592 $0 = declare_function(c, $<FN, NULL, NULL, $<Ar, $<Bl);
5595 ###### print func decls
5600 while (target != 0) {
5602 for (v = context.in_scope; v; v=v->in_scope)
5603 if (v->depth == 0 && v->type && v->type->check_args) {
5612 struct value *val = var_value(&context, v);
5613 printf("func %.*s", v->name->name.len, v->name->name.txt);
5614 v->type->print_type_decl(v->type, stdout);
5616 print_exec(val->function, 0, brackets);
5618 print_value(v->type, val, stdout);
5619 printf("/* frame size %d */\n", v->type->function.local_size);
5625 ###### core functions
5627 static int analyse_funcs(struct parse_context *c)
5631 for (v = c->in_scope; v; v = v->in_scope) {
5635 if (v->depth != 0 || !v->type || !v->type->check_args)
5637 ret = v->type->function.inline_result ?
5638 Tnone : v->type->function.return_type;
5639 val = var_value(c, v);
5642 propagate_types(val->function, c, &perr, ret, 0);
5643 } while (!(perr & Efail) && (perr & Eretry));
5644 if (!(perr & Efail))
5645 /* Make sure everything is still consistent */
5646 propagate_types(val->function, c, &perr, ret, 0);
5649 if (!v->type->function.inline_result &&
5650 !v->type->function.return_type->dup) {
5651 type_err(c, "error: function cannot return value of type %1",
5652 v->where_decl, v->type->function.return_type, 0, NULL);
5655 scope_finalize(c, v->type);
5660 static int analyse_main(struct type *type, struct parse_context *c)
5662 struct binode *bp = type->function.params;
5666 struct type *argv_type;
5668 argv_type = add_anon_type(c, &array_prototype, "argv");
5669 argv_type->array.member = Tstr;
5670 argv_type->array.unspec = 1;
5672 for (b = bp; b; b = cast(binode, b->right)) {
5676 propagate_types(b->left, c, &perr, argv_type, 0);
5678 default: /* invalid */ // NOTEST
5679 propagate_types(b->left, c, &perr, Tnone, 0); // NOTEST
5682 c->parse_error += 1;
5685 return !c->parse_error;
5688 static void interp_main(struct parse_context *c, int argc, char **argv)
5690 struct value *progp = NULL;
5691 struct text main_name = { "main", 4 };
5692 struct variable *mainv;
5698 mainv = var_ref(c, main_name);
5700 progp = var_value(c, mainv);
5701 if (!progp || !progp->function) {
5702 fprintf(stderr, "oceani: no main function found.\n");
5703 c->parse_error += 1;
5706 if (!analyse_main(mainv->type, c)) {
5707 fprintf(stderr, "oceani: main has wrong type.\n");
5708 c->parse_error += 1;
5711 al = mainv->type->function.params;
5713 c->local_size = mainv->type->function.local_size;
5714 c->local = calloc(1, c->local_size);
5716 struct var *v = cast(var, al->left);
5717 struct value *vl = var_value(c, v->var);
5727 mpq_set_ui(argcq, argc, 1);
5728 memcpy(var_value(c, t->array.vsize), &argcq, sizeof(argcq));
5729 t->prepare_type(c, t, 0);
5730 array_init(v->var->type, vl);
5731 for (i = 0; i < argc; i++) {
5732 struct value *vl2 = vl->array + i * v->var->type->array.member->size;
5734 arg.str.txt = argv[i];
5735 arg.str.len = strlen(argv[i]);
5736 free_value(Tstr, vl2);
5737 dup_value(Tstr, &arg, vl2);
5741 al = cast(binode, al->right);
5743 v = interp_exec(c, progp->function, &vtype);
5744 free_value(vtype, &v);
5749 ###### ast functions
5750 void free_variable(struct variable *v)
5754 ## And now to test it out.
5756 Having a language requires having a "hello world" program. I'll
5757 provide a little more than that: a program that prints "Hello world"
5758 finds the GCD of two numbers, prints the first few elements of
5759 Fibonacci, performs a binary search for a number, and a few other
5760 things which will likely grow as the languages grows.
5762 ###### File: oceani.mk
5765 @echo "===== DEMO ====="
5766 ./oceani --section "demo: hello" oceani.mdc 55 33
5772 four ::= 2 + 2 ; five ::= 10/2
5773 const pie ::= "I like Pie";
5774 cake ::= "The cake is"
5782 func main(argv:[argc::]string)
5783 print "Hello World, what lovely oceans you have!"
5784 print "Are there", five, "?"
5785 print pi, pie, "but", cake
5787 A := $argv[1]; B := $argv[2]
5789 /* When a variable is defined in both branches of an 'if',
5790 * and used afterwards, the variables are merged.
5796 print "Is", A, "bigger than", B,"? ", bigger
5797 /* If a variable is not used after the 'if', no
5798 * merge happens, so types can be different
5801 double:string = "yes"
5802 print A, "is more than twice", B, "?", double
5805 print "double", B, "is", double
5810 if a > 0 and then b > 0:
5816 print "GCD of", A, "and", B,"is", a
5818 print a, "is not positive, cannot calculate GCD"
5820 print b, "is not positive, cannot calculate GCD"
5825 print "Fibonacci:", f1,f2,
5826 then togo = togo - 1
5834 /* Binary search... */
5839 mid := (lo + hi) / 2
5852 print "Yay, I found", target
5854 print "Closest I found was", lo
5859 // "middle square" PRNG. Not particularly good, but one my
5860 // Dad taught me - the first one I ever heard of.
5861 for i:=1; then i = i + 1; while i < size:
5862 n := list[i-1] * list[i-1]
5863 list[i] = (n / 100) % 10 000
5865 print "Before sort:",
5866 for i:=0; then i = i + 1; while i < size:
5870 for i := 1; then i=i+1; while i < size:
5871 for j:=i-1; then j=j-1; while j >= 0:
5872 if list[j] > list[j+1]:
5876 print " After sort:",
5877 for i:=0; then i = i + 1; while i < size:
5881 if 1 == 2 then print "yes"; else print "no"
5885 bob.alive = (bob.name == "Hello")
5886 print "bob", "is" if bob.alive else "isn't", "alive"