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, *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
243 parse_oceani(ss->code, &context.config, dotrace ? stderr : NULL);
245 if (!context.parse_error && !analyse_funcs(&context)) {
246 fprintf(stderr, "oceani: type error in program - not running.\n");
247 context.parse_error = 1;
255 if (doexec && !context.parse_error)
256 interp_main(&context, argc - optind, argv + optind);
259 struct section *t = s->next;
264 if (!context.parse_error) {
267 ## free context types
268 ## free context storage
269 exit(context.parse_error ? 1 : 0);
274 The four requirements of parse, analyse, print, interpret apply to
275 each language element individually so that is how most of the code
278 Three of the four are fairly self explanatory. The one that requires
279 a little explanation is the analysis step.
281 The current language design does not require the types of variables to
282 be declared, but they must still have a single type. Different
283 operations impose different requirements on the variables, for example
284 addition requires both arguments to be numeric, and assignment
285 requires the variable on the left to have the same type as the
286 expression on the right.
288 Analysis involves propagating these type requirements around and
289 consequently setting the type of each variable. If any requirements
290 are violated (e.g. a string is compared with a number) or if a
291 variable needs to have two different types, then an error is raised
292 and the program will not run.
294 If the same variable is declared in both branchs of an 'if/else', or
295 in all cases of a 'switch' then the multiple instances may be merged
296 into just one variable if the variable is referenced after the
297 conditional statement. When this happens, the types must naturally be
298 consistent across all the branches. When the variable is not used
299 outside the if, the variables in the different branches are distinct
300 and can be of different types.
302 Undeclared names may only appear in "use" statements and "case" expressions.
303 These names are given a type of "label" and a unique value.
304 This allows them to fill the role of a name in an enumerated type, which
305 is useful for testing the `switch` statement.
307 As we will see, the condition part of a `while` statement can return
308 either a Boolean or some other type. This requires that the expected
309 type that gets passed around comprises a type and a flag to indicate
310 that `Tbool` is also permitted.
312 As there are, as yet, no distinct types that are compatible, there
313 isn't much subtlety in the analysis. When we have distinct number
314 types, this will become more interesting.
318 When analysis discovers an inconsistency it needs to report an error;
319 just refusing to run the code ensures that the error doesn't cascade,
320 but by itself it isn't very useful. A clear understanding of the sort
321 of error message that are useful will help guide the process of
324 At a simplistic level, the only sort of error that type analysis can
325 report is that the type of some construct doesn't match a contextual
326 requirement. For example, in `4 + "hello"` the addition provides a
327 contextual requirement for numbers, but `"hello"` is not a number. In
328 this particular example no further information is needed as the types
329 are obvious from local information. When a variable is involved that
330 isn't the case. It may be helpful to explain why the variable has a
331 particular type, by indicating the location where the type was set,
332 whether by declaration or usage.
334 Using a recursive-descent analysis we can easily detect a problem at
335 multiple locations. In "`hello:= "there"; 4 + hello`" the addition
336 will detect that one argument is not a number and the usage of `hello`
337 will detect that a number was wanted, but not provided. In this
338 (early) version of the language, we will generate error reports at
339 multiple locations, so the use of `hello` will report an error and
340 explain were the value was set, and the addition will report an error
341 and say why numbers are needed. To be able to report locations for
342 errors, each language element will need to record a file location
343 (line and column) and each variable will need to record the language
344 element where its type was set. For now we will assume that each line
345 of an error message indicates one location in the file, and up to 2
346 types. So we provide a `printf`-like function which takes a format, a
347 location (a `struct exec` which has not yet been introduced), and 2
348 types. "`%1`" reports the first type, "`%2`" reports the second. We
349 will need a function to print the location, once we know how that is
350 stored. e As will be explained later, there are sometimes extra rules for
351 type matching and they might affect error messages, we need to pass those
354 As well as type errors, we sometimes need to report problems with
355 tokens, which might be unexpected or might name a type that has not
356 been defined. For these we have `tok_err()` which reports an error
357 with a given token. Each of the error functions sets the flag in the
358 context so indicate that parsing failed.
362 static void fput_loc(struct exec *loc, FILE *f);
363 static void type_err(struct parse_context *c,
364 char *fmt, struct exec *loc,
365 struct type *t1, int rules, struct type *t2);
367 ###### core functions
369 static void type_err(struct parse_context *c,
370 char *fmt, struct exec *loc,
371 struct type *t1, int rules, struct type *t2)
373 fprintf(stderr, "%s:", c->file_name);
374 fput_loc(loc, stderr);
375 for (; *fmt ; fmt++) {
382 case '%': fputc(*fmt, stderr); break; // NOTEST
383 default: fputc('?', stderr); break; // NOTEST
385 type_print(t1, stderr);
388 type_print(t2, stderr);
397 static void tok_err(struct parse_context *c, char *fmt, struct token *t)
399 fprintf(stderr, "%s:%d:%d: %s: %.*s\n", c->file_name, t->line, t->col, fmt,
400 t->txt.len, t->txt.txt);
404 ## Entities: declared and predeclared.
406 There are various "things" that the language and/or the interpreter
407 needs to know about to parse and execute a program. These include
408 types, variables, values, and executable code. These are all lumped
409 together under the term "entities" (calling them "objects" would be
410 confusing) and introduced here. The following section will present the
411 different specific code elements which comprise or manipulate these
416 Values come in a wide range of types, with more likely to be added.
417 Each type needs to be able to print its own values (for convenience at
418 least) as well as to compare two values, at least for equality and
419 possibly for order. For now, values might need to be duplicated and
420 freed, though eventually such manipulations will be better integrated
423 Rather than requiring every numeric type to support all numeric
424 operations (add, multiple, etc), we allow types to be able to present
425 as one of a few standard types: integer, float, and fraction. The
426 existence of these conversion functions eventually enable types to
427 determine if they are compatible with other types, though such types
428 have not yet been implemented.
430 Named type are stored in a simple linked list. Objects of each type are
431 "values" which are often passed around by value.
438 ## value union fields
446 void (*init)(struct type *type, struct value *val);
447 void (*prepare_type)(struct parse_context *c, struct type *type, int parse_time);
448 void (*print)(struct type *type, struct value *val);
449 void (*print_type)(struct type *type, FILE *f);
450 int (*cmp_order)(struct type *t1, struct type *t2,
451 struct value *v1, struct value *v2);
452 int (*cmp_eq)(struct type *t1, struct type *t2,
453 struct value *v1, struct value *v2);
454 void (*dup)(struct type *type, struct value *vold, struct value *vnew);
455 void (*free)(struct type *type, struct value *val);
456 void (*free_type)(struct type *t);
457 long long (*to_int)(struct value *v);
458 double (*to_float)(struct value *v);
459 int (*to_mpq)(mpq_t *q, struct value *v);
468 struct type *typelist;
472 static struct type *find_type(struct parse_context *c, struct text s)
474 struct type *l = c->typelist;
477 text_cmp(l->name, s) != 0)
482 static struct type *add_type(struct parse_context *c, struct text s,
487 n = calloc(1, sizeof(*n));
490 n->next = c->typelist;
495 static void free_type(struct type *t)
497 /* The type is always a reference to something in the
498 * context, so we don't need to free anything.
502 static void free_value(struct type *type, struct value *v)
506 memset(v, 0x5a, type->size);
510 static void type_print(struct type *type, FILE *f)
513 fputs("*unknown*type*", f); // NOTEST
514 else if (type->name.len)
515 fprintf(f, "%.*s", type->name.len, type->name.txt);
516 else if (type->print_type)
517 type->print_type(type, f);
519 fputs("*invalid*type*", f); // NOTEST
522 static void val_init(struct type *type, struct value *val)
524 if (type && type->init)
525 type->init(type, val);
528 static void dup_value(struct type *type,
529 struct value *vold, struct value *vnew)
531 if (type && type->dup)
532 type->dup(type, vold, vnew);
535 static int value_cmp(struct type *tl, struct type *tr,
536 struct value *left, struct value *right)
538 if (tl && tl->cmp_order)
539 return tl->cmp_order(tl, tr, left, right);
540 if (tl && tl->cmp_eq) // NOTEST
541 return tl->cmp_eq(tl, tr, left, right); // NOTEST
545 static void print_value(struct type *type, struct value *v)
547 if (type && type->print)
548 type->print(type, v);
550 printf("*Unknown*"); // NOTEST
555 static void free_value(struct type *type, struct value *v);
556 static int type_compat(struct type *require, struct type *have, int rules);
557 static void type_print(struct type *type, FILE *f);
558 static void val_init(struct type *type, struct value *v);
559 static void dup_value(struct type *type,
560 struct value *vold, struct value *vnew);
561 static int value_cmp(struct type *tl, struct type *tr,
562 struct value *left, struct value *right);
563 static void print_value(struct type *type, struct value *v);
565 ###### free context types
567 while (context.typelist) {
568 struct type *t = context.typelist;
570 context.typelist = t->next;
576 Type can be specified for local variables, for fields in a structure,
577 for formal parameters to functions, and possibly elsewhere. Different
578 rules may apply in different contexts. As a minimum, a named type may
579 always be used. Currently the type of a formal parameter can be
580 different from types in other contexts, so we have a separate grammar
586 Type -> IDENTIFIER ${
587 $0 = find_type(c, $1.txt);
590 "error: undefined type", &$1);
597 FormalType -> Type ${ $0 = $<1; }$
598 ## formal type grammar
602 Values of the base types can be numbers, which we represent as
603 multi-precision fractions, strings, Booleans and labels. When
604 analysing the program we also need to allow for places where no value
605 is meaningful (type `Tnone`) and where we don't know what type to
606 expect yet (type is `NULL`).
608 Values are never shared, they are always copied when used, and freed
609 when no longer needed.
611 When propagating type information around the program, we need to
612 determine if two types are compatible, where type `NULL` is compatible
613 with anything. There are two special cases with type compatibility,
614 both related to the Conditional Statement which will be described
615 later. In some cases a Boolean can be accepted as well as some other
616 primary type, and in others any type is acceptable except a label (`Vlabel`).
617 A separate function encoding these cases will simplify some code later.
619 ###### type functions
621 int (*compat)(struct type *this, struct type *other);
625 static int type_compat(struct type *require, struct type *have, int rules)
627 if ((rules & Rboolok) && have == Tbool)
629 if ((rules & Rnolabel) && have == Tlabel)
631 if (!require || !have)
635 return require->compat(require, have);
637 return require == have;
642 #include "parse_string.h"
643 #include "parse_number.h"
646 myLDLIBS := libnumber.o libstring.o -lgmp
647 LDLIBS := $(filter-out $(myLDLIBS),$(LDLIBS)) $(myLDLIBS)
649 ###### type union fields
650 enum vtype {Vnone, Vstr, Vnum, Vbool, Vlabel} vtype;
652 ###### value union fields
659 static void _free_value(struct type *type, struct value *v)
663 switch (type->vtype) {
665 case Vstr: free(v->str.txt); break;
666 case Vnum: mpq_clear(v->num); break;
672 ###### value functions
674 static void _val_init(struct type *type, struct value *val)
676 switch(type->vtype) {
677 case Vnone: // NOTEST
680 mpq_init(val->num); break;
682 val->str.txt = malloc(1);
694 static void _dup_value(struct type *type,
695 struct value *vold, struct value *vnew)
697 switch (type->vtype) {
698 case Vnone: // NOTEST
701 vnew->label = vold->label;
704 vnew->bool = vold->bool;
708 mpq_set(vnew->num, vold->num);
711 vnew->str.len = vold->str.len;
712 vnew->str.txt = malloc(vnew->str.len);
713 memcpy(vnew->str.txt, vold->str.txt, vnew->str.len);
718 static int _value_cmp(struct type *tl, struct type *tr,
719 struct value *left, struct value *right)
723 return tl - tr; // NOTEST
725 case Vlabel: cmp = left->label == right->label ? 0 : 1; break;
726 case Vnum: cmp = mpq_cmp(left->num, right->num); break;
727 case Vstr: cmp = text_cmp(left->str, right->str); break;
728 case Vbool: cmp = left->bool - right->bool; break;
729 case Vnone: cmp = 0; // NOTEST
734 static void _print_value(struct type *type, struct value *v)
736 switch (type->vtype) {
737 case Vnone: // NOTEST
738 printf("*no-value*"); break; // NOTEST
739 case Vlabel: // NOTEST
740 printf("*label-%p*", v->label); break; // NOTEST
742 printf("%.*s", v->str.len, v->str.txt); break;
744 printf("%s", v->bool ? "True":"False"); break;
749 mpf_set_q(fl, v->num);
750 gmp_printf("%Fg", fl);
757 static void _free_value(struct type *type, struct value *v);
759 static struct type base_prototype = {
761 .print = _print_value,
762 .cmp_order = _value_cmp,
763 .cmp_eq = _value_cmp,
768 static struct type *Tbool, *Tstr, *Tnum, *Tnone, *Tlabel;
771 static struct type *add_base_type(struct parse_context *c, char *n,
772 enum vtype vt, int size)
774 struct text txt = { n, strlen(n) };
777 t = add_type(c, txt, &base_prototype);
780 t->align = size > sizeof(void*) ? sizeof(void*) : size;
781 if (t->size & (t->align - 1))
782 t->size = (t->size | (t->align - 1)) + 1; // NOTEST
786 ###### context initialization
788 Tbool = add_base_type(&context, "Boolean", Vbool, sizeof(char));
789 Tstr = add_base_type(&context, "string", Vstr, sizeof(struct text));
790 Tnum = add_base_type(&context, "number", Vnum, sizeof(mpq_t));
791 Tnone = add_base_type(&context, "none", Vnone, 0);
792 Tlabel = add_base_type(&context, "label", Vlabel, sizeof(void*));
796 Variables are scoped named values. We store the names in a linked list
797 of "bindings" sorted in lexical order, and use sequential search and
804 struct binding *next; // in lexical order
808 This linked list is stored in the parse context so that "reduce"
809 functions can find or add variables, and so the analysis phase can
810 ensure that every variable gets a type.
814 struct binding *varlist; // In lexical order
818 static struct binding *find_binding(struct parse_context *c, struct text s)
820 struct binding **l = &c->varlist;
825 (cmp = text_cmp((*l)->name, s)) < 0)
829 n = calloc(1, sizeof(*n));
836 Each name can be linked to multiple variables defined in different
837 scopes. Each scope starts where the name is declared and continues
838 until the end of the containing code block. Scopes of a given name
839 cannot nest, so a declaration while a name is in-scope is an error.
841 ###### binding fields
842 struct variable *var;
846 struct variable *previous;
848 struct binding *name;
849 struct exec *where_decl;// where name was declared
850 struct exec *where_set; // where type was set
854 When a scope closes, the values of the variables might need to be freed.
855 This happens in the context of some `struct exec` and each `exec` will
856 need to know which variables need to be freed when it completes.
859 struct variable *to_free;
861 ####### variable fields
862 struct exec *cleanup_exec;
863 struct variable *next_free;
865 ####### interp exec cleanup
868 for (v = e->to_free; v; v = v->next_free) {
869 struct value *val = var_value(c, v);
870 free_value(v->type, val);
875 static void variable_unlink_exec(struct variable *v)
877 struct variable **vp;
878 if (!v->cleanup_exec)
880 for (vp = &v->cleanup_exec->to_free;
881 *vp; vp = &(*vp)->next_free) {
885 v->cleanup_exec = NULL;
890 While the naming seems strange, we include local constants in the
891 definition of variables. A name declared `var := value` can
892 subsequently be changed, but a name declared `var ::= value` cannot -
895 ###### variable fields
898 Scopes in parallel branches can be partially merged. More
899 specifically, if a given name is declared in both branches of an
900 if/else then its scope is a candidate for merging. Similarly if
901 every branch of an exhaustive switch (e.g. has an "else" clause)
902 declares a given name, then the scopes from the branches are
903 candidates for merging.
905 Note that names declared inside a loop (which is only parallel to
906 itself) are never visible after the loop. Similarly names defined in
907 scopes which are not parallel, such as those started by `for` and
908 `switch`, are never visible after the scope. Only variables defined in
909 both `then` and `else` (including the implicit then after an `if`, and
910 excluding `then` used with `for`) and in all `case`s and `else` of a
911 `switch` or `while` can be visible beyond the `if`/`switch`/`while`.
913 Labels, which are a bit like variables, follow different rules.
914 Labels are not explicitly declared, but if an undeclared name appears
915 in a context where a label is legal, that effectively declares the
916 name as a label. The declaration remains in force (or in scope) at
917 least to the end of the immediately containing block and conditionally
918 in any larger containing block which does not declare the name in some
919 other way. Importantly, the conditional scope extension happens even
920 if the label is only used in one parallel branch of a conditional --
921 when used in one branch it is treated as having been declared in all
924 Merge candidates are tentatively visible beyond the end of the
925 branching statement which creates them. If the name is used, the
926 merge is affirmed and they become a single variable visible at the
927 outer layer. If not - if it is redeclared first - the merge lapses.
929 To track scopes we have an extra stack, implemented as a linked list,
930 which roughly parallels the parse stack and which is used exclusively
931 for scoping. When a new scope is opened, a new frame is pushed and
932 the child-count of the parent frame is incremented. This child-count
933 is used to distinguish between the first of a set of parallel scopes,
934 in which declared variables must not be in scope, and subsequent
935 branches, whether they may already be conditionally scoped.
937 To push a new frame *before* any code in the frame is parsed, we need a
938 grammar reduction. This is most easily achieved with a grammar
939 element which derives the empty string, and creates the new scope when
940 it is recognised. This can be placed, for example, between a keyword
941 like "if" and the code following it.
945 struct scope *parent;
951 struct scope *scope_stack;
954 static void scope_pop(struct parse_context *c)
956 struct scope *s = c->scope_stack;
958 c->scope_stack = s->parent;
963 static void scope_push(struct parse_context *c)
965 struct scope *s = calloc(1, sizeof(*s));
967 c->scope_stack->child_count += 1;
968 s->parent = c->scope_stack;
976 OpenScope -> ${ scope_push(c); }$
978 Each variable records a scope depth and is in one of four states:
980 - "in scope". This is the case between the declaration of the
981 variable and the end of the containing block, and also between
982 the usage with affirms a merge and the end of that block.
984 The scope depth is not greater than the current parse context scope
985 nest depth. When the block of that depth closes, the state will
986 change. To achieve this, all "in scope" variables are linked
987 together as a stack in nesting order.
989 - "pending". The "in scope" block has closed, but other parallel
990 scopes are still being processed. So far, every parallel block at
991 the same level that has closed has declared the name.
993 The scope depth is the depth of the last parallel block that
994 enclosed the declaration, and that has closed.
996 - "conditionally in scope". The "in scope" block and all parallel
997 scopes have closed, and no further mention of the name has been seen.
998 This state includes a secondary nest depth (`min_depth`) which records
999 the outermost scope seen since the variable became conditionally in
1000 scope. If a use of the name is found, the variable becomes "in scope"
1001 and that secondary depth becomes the recorded scope depth. If the
1002 name is declared as a new variable, the old variable becomes "out of
1003 scope" and the recorded scope depth stays unchanged.
1005 - "out of scope". The variable is neither in scope nor conditionally
1006 in scope. It is permanently out of scope now and can be removed from
1007 the "in scope" stack.
1009 ###### variable fields
1010 int depth, min_depth;
1011 enum { OutScope, PendingScope, CondScope, InScope } scope;
1012 struct variable *in_scope;
1014 ###### parse context
1016 struct variable *in_scope;
1018 All variables with the same name are linked together using the
1019 'previous' link. Those variable that have been affirmatively merged all
1020 have a 'merged' pointer that points to one primary variable - the most
1021 recently declared instance. When merging variables, we need to also
1022 adjust the 'merged' pointer on any other variables that had previously
1023 been merged with the one that will no longer be primary.
1025 A variable that is no longer the most recent instance of a name may
1026 still have "pending" scope, if it might still be merged with most
1027 recent instance. These variables don't really belong in the
1028 "in_scope" list, but are not immediately removed when a new instance
1029 is found. Instead, they are detected and ignored when considering the
1030 list of in_scope names.
1032 The storage of the value of a variable will be described later. For now
1033 we just need to know that when a variable goes out of scope, it might
1034 need to be freed. For this we need to be able to find it, so assume that
1035 `var_value()` will provide that.
1037 ###### variable fields
1038 struct variable *merged;
1040 ###### ast functions
1042 static void variable_merge(struct variable *primary, struct variable *secondary)
1046 primary = primary->merged;
1048 for (v = primary->previous; v; v=v->previous)
1049 if (v == secondary || v == secondary->merged ||
1050 v->merged == secondary ||
1051 v->merged == secondary->merged) {
1052 v->scope = OutScope;
1053 v->merged = primary;
1054 variable_unlink_exec(v);
1058 ###### forward decls
1059 static struct value *var_value(struct parse_context *c, struct variable *v);
1061 ###### free global vars
1063 while (context.varlist) {
1064 struct binding *b = context.varlist;
1065 struct variable *v = b->var;
1066 context.varlist = b->next;
1069 struct variable *next = v->previous;
1072 free_value(v->type, var_value(&context, v));
1074 // This is a global constant
1075 free_exec(v->where_decl);
1082 #### Manipulating Bindings
1084 When a name is conditionally visible, a new declaration discards the
1085 old binding - the condition lapses. Conversely a usage of the name
1086 affirms the visibility and extends it to the end of the containing
1087 block - i.e. the block that contains both the original declaration and
1088 the latest usage. This is determined from `min_depth`. When a
1089 conditionally visible variable gets affirmed like this, it is also
1090 merged with other conditionally visible variables with the same name.
1092 When we parse a variable declaration we either report an error if the
1093 name is currently bound, or create a new variable at the current nest
1094 depth if the name is unbound or bound to a conditionally scoped or
1095 pending-scope variable. If the previous variable was conditionally
1096 scoped, it and its homonyms becomes out-of-scope.
1098 When we parse a variable reference (including non-declarative assignment
1099 "foo = bar") we report an error if the name is not bound or is bound to
1100 a pending-scope variable; update the scope if the name is bound to a
1101 conditionally scoped variable; or just proceed normally if the named
1102 variable is in scope.
1104 When we exit a scope, any variables bound at this level are either
1105 marked out of scope or pending-scoped, depending on whether the scope
1106 was sequential or parallel. Here a "parallel" scope means the "then"
1107 or "else" part of a conditional, or any "case" or "else" branch of a
1108 switch. Other scopes are "sequential".
1110 When exiting a parallel scope we check if there are any variables that
1111 were previously pending and are still visible. If there are, then
1112 they weren't redeclared in the most recent scope, so they cannot be
1113 merged and must become out-of-scope. If it is not the first of
1114 parallel scopes (based on `child_count`), we check that there was a
1115 previous binding that is still pending-scope. If there isn't, the new
1116 variable must now be out-of-scope.
1118 When exiting a sequential scope that immediately enclosed parallel
1119 scopes, we need to resolve any pending-scope variables. If there was
1120 no `else` clause, and we cannot determine that the `switch` was exhaustive,
1121 we need to mark all pending-scope variable as out-of-scope. Otherwise
1122 all pending-scope variables become conditionally scoped.
1125 enum closetype { CloseSequential, CloseParallel, CloseElse };
1127 ###### ast functions
1129 static struct variable *var_decl(struct parse_context *c, struct text s)
1131 struct binding *b = find_binding(c, s);
1132 struct variable *v = b->var;
1134 switch (v ? v->scope : OutScope) {
1136 /* Caller will report the error */
1140 v && v->scope == CondScope;
1142 v->scope = OutScope;
1146 v = calloc(1, sizeof(*v));
1147 v->previous = b->var;
1151 v->min_depth = v->depth = c->scope_depth;
1153 v->in_scope = c->in_scope;
1159 static struct variable *var_ref(struct parse_context *c, struct text s)
1161 struct binding *b = find_binding(c, s);
1162 struct variable *v = b->var;
1163 struct variable *v2;
1165 switch (v ? v->scope : OutScope) {
1168 /* Caller will report the error */
1171 /* All CondScope variables of this name need to be merged
1172 * and become InScope
1174 v->depth = v->min_depth;
1176 for (v2 = v->previous;
1177 v2 && v2->scope == CondScope;
1179 variable_merge(v, v2);
1187 static void var_block_close(struct parse_context *c, enum closetype ct,
1190 /* Close off all variables that are in_scope.
1191 * Some variables in c->scope may already be not-in-scope,
1192 * such as when a PendingScope variable is hidden by a new
1193 * variable with the same name.
1194 * So we check for v->name->var != v and drop them.
1195 * If we choose to make a variable OutScope, we drop it
1198 struct variable *v, **vp, *v2;
1201 for (vp = &c->in_scope;
1202 (v = *vp) && v->min_depth > c->scope_depth;
1203 (v->scope == OutScope || v->name->var != v)
1204 ? (*vp = v->in_scope, 0)
1205 : ( vp = &v->in_scope, 0)) {
1206 v->min_depth = c->scope_depth;
1207 if (v->name->var != v)
1208 /* This is still in scope, but we haven't just
1212 v->min_depth = c->scope_depth;
1213 if (v->scope == InScope && e) {
1214 /* This variable gets cleaned up when 'e' finishes */
1215 variable_unlink_exec(v);
1216 v->cleanup_exec = e;
1217 v->next_free = e->to_free;
1222 case CloseParallel: /* handle PendingScope */
1226 if (c->scope_stack->child_count == 1)
1227 /* first among parallel branches */
1228 v->scope = PendingScope;
1229 else if (v->previous &&
1230 v->previous->scope == PendingScope)
1231 /* all previous branches used name */
1232 v->scope = PendingScope;
1233 else if (v->type == Tlabel)
1234 /* Labels remain pending even when not used */
1235 v->scope = PendingScope; // UNTESTED
1237 v->scope = OutScope;
1238 if (ct == CloseElse) {
1239 /* All Pending variables with this name
1240 * are now Conditional */
1242 v2 && v2->scope == PendingScope;
1244 v2->scope = CondScope;
1248 /* Not possible as it would require
1249 * parallel scope to be nested immediately
1250 * in a parallel scope, and that never
1254 /* Not possible as we already tested for
1260 case CloseSequential:
1261 if (v->type == Tlabel)
1262 v->scope = PendingScope;
1265 v->scope = OutScope;
1268 /* There was no 'else', so we can only become
1269 * conditional if we know the cases were exhaustive,
1270 * and that doesn't mean anything yet.
1271 * So only labels become conditional..
1274 v2 && v2->scope == PendingScope;
1276 if (v2->type == Tlabel)
1277 v2->scope = CondScope;
1279 v2->scope = OutScope;
1282 case OutScope: break;
1291 The value of a variable is store separately from the variable, on an
1292 analogue of a stack frame. There are (currently) two frames that can be
1293 active. A global frame which currently only stores constants, and a
1294 stacked frame which stores local variables. Each variable knows if it
1295 is global or not, and what its index into the frame is.
1297 Values in the global frame are known immediately they are relevant, so
1298 the frame needs to be reallocated as it grows so it can store those
1299 values. The local frame doesn't get values until the interpreted phase
1300 is started, so there is no need to allocate until the size is known.
1302 We initialize the `frame_pos` to an impossible value, so that we can
1303 tell if it was set or not later.
1305 ###### variable fields
1309 ###### variable init
1312 ###### parse context
1314 short global_size, global_alloc;
1316 void *global, *local;
1318 ###### ast functions
1320 static struct value *var_value(struct parse_context *c, struct variable *v)
1323 if (!c->local || !v->type)
1324 return NULL; // NOTEST
1325 if (v->frame_pos + v->type->size > c->local_size) {
1326 printf("INVALID frame_pos\n"); // NOTEST
1329 return c->local + v->frame_pos;
1331 if (c->global_size > c->global_alloc) {
1332 int old = c->global_alloc;
1333 c->global_alloc = (c->global_size | 1023) + 1024;
1334 c->global = realloc(c->global, c->global_alloc);
1335 memset(c->global + old, 0, c->global_alloc - old);
1337 return c->global + v->frame_pos;
1340 static struct value *global_alloc(struct parse_context *c, struct type *t,
1341 struct variable *v, struct value *init)
1344 struct variable scratch;
1346 if (t->prepare_type)
1347 t->prepare_type(c, t, 1); // NOTEST
1349 if (c->global_size & (t->align - 1))
1350 c->global_size = (c->global_size + t->align) & ~(t->align-1);
1355 v->frame_pos = c->global_size;
1357 c->global_size += v->type->size;
1358 ret = var_value(c, v);
1360 memcpy(ret, init, t->size);
1366 As global values are found -- struct field initializers, labels etc --
1367 `global_alloc()` is called to record the value in the global frame.
1369 When the program is fully parsed, we need to walk the list of variables
1370 to find any that weren't merged away and that aren't global, and to
1371 calculate the frame size and assign a frame position for each
1372 variable. For this we have `scope_finalize()`.
1374 ###### ast functions
1376 static int scope_finalize(struct parse_context *c)
1381 for (b = c->varlist; b; b = b->next) {
1383 for (v = b->var; v; v = v->previous) {
1384 struct type *t = v->type;
1391 if (size & (t->align - 1))
1392 size = (size + t->align) & ~(t->align-1);
1393 v->frame_pos = size;
1394 size += v->type->size;
1400 ###### free context storage
1401 free(context.global);
1405 Executables can be lots of different things. In many cases an
1406 executable is just an operation combined with one or two other
1407 executables. This allows for expressions and lists etc. Other times an
1408 executable is something quite specific like a constant or variable name.
1409 So we define a `struct exec` to be a general executable with a type, and
1410 a `struct binode` which is a subclass of `exec`, forms a node in a
1411 binary tree, and holds an operation. There will be other subclasses,
1412 and to access these we need to be able to `cast` the `exec` into the
1413 various other types. The first field in any `struct exec` is the type
1414 from the `exec_types` enum.
1417 #define cast(structname, pointer) ({ \
1418 const typeof( ((struct structname *)0)->type) *__mptr = &(pointer)->type; \
1419 if (__mptr && *__mptr != X##structname) abort(); \
1420 (struct structname *)( (char *)__mptr);})
1422 #define new(structname) ({ \
1423 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1424 __ptr->type = X##structname; \
1425 __ptr->line = -1; __ptr->column = -1; \
1428 #define new_pos(structname, token) ({ \
1429 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1430 __ptr->type = X##structname; \
1431 __ptr->line = token.line; __ptr->column = token.col; \
1440 enum exec_types type;
1449 struct exec *left, *right;
1452 ###### ast functions
1454 static int __fput_loc(struct exec *loc, FILE *f)
1458 if (loc->line >= 0) {
1459 fprintf(f, "%d:%d: ", loc->line, loc->column);
1462 if (loc->type == Xbinode)
1463 return __fput_loc(cast(binode,loc)->left, f) ||
1464 __fput_loc(cast(binode,loc)->right, f); // NOTEST
1467 static void fput_loc(struct exec *loc, FILE *f)
1469 if (!__fput_loc(loc, f))
1470 fprintf(f, "??:??: ");
1473 Each different type of `exec` node needs a number of functions defined,
1474 a bit like methods. We must be able to free it, print it, analyse it
1475 and execute it. Once we have specific `exec` types we will need to
1476 parse them too. Let's take this a bit more slowly.
1480 The parser generator requires a `free_foo` function for each struct
1481 that stores attributes and they will often be `exec`s and subtypes
1482 there-of. So we need `free_exec` which can handle all the subtypes,
1483 and we need `free_binode`.
1485 ###### ast functions
1487 static void free_binode(struct binode *b)
1492 free_exec(b->right);
1496 ###### core functions
1497 static void free_exec(struct exec *e)
1506 ###### forward decls
1508 static void free_exec(struct exec *e);
1510 ###### free exec cases
1511 case Xbinode: free_binode(cast(binode, e)); break;
1515 Printing an `exec` requires that we know the current indent level for
1516 printing line-oriented components. As will become clear later, we
1517 also want to know what sort of bracketing to use.
1519 ###### ast functions
1521 static void do_indent(int i, char *str)
1528 ###### core functions
1529 static void print_binode(struct binode *b, int indent, int bracket)
1533 ## print binode cases
1537 static void print_exec(struct exec *e, int indent, int bracket)
1543 print_binode(cast(binode, e), indent, bracket); break;
1548 do_indent(indent, "/* FREE");
1549 for (v = e->to_free; v; v = v->next_free) {
1550 printf(" %.*s", v->name->name.len, v->name->name.txt);
1551 if (v->frame_pos >= 0)
1552 printf("(%d+%d)", v->frame_pos,
1553 v->type ? v->type->size:0);
1559 ###### forward decls
1561 static void print_exec(struct exec *e, int indent, int bracket);
1565 As discussed, analysis involves propagating type requirements around the
1566 program and looking for errors.
1568 So `propagate_types` is passed an expected type (being a `struct type`
1569 pointer together with some `val_rules` flags) that the `exec` is
1570 expected to return, and returns the type that it does return, either
1571 of which can be `NULL` signifying "unknown". An `ok` flag is passed
1572 by reference. It is set to `0` when an error is found, and `2` when
1573 any change is made. If it remains unchanged at `1`, then no more
1574 propagation is needed.
1578 enum val_rules {Rnolabel = 1<<0, Rboolok = 1<<1, Rnoconstant = 1<<2};
1582 if (rules & Rnolabel)
1583 fputs(" (labels not permitted)", stderr);
1586 ###### forward decls
1587 static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1588 struct type *type, int rules);
1589 ###### core functions
1591 static struct type *__propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1592 struct type *type, int rules)
1599 switch (prog->type) {
1602 struct binode *b = cast(binode, prog);
1604 ## propagate binode cases
1608 ## propagate exec cases
1613 static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1614 struct type *type, int rules)
1616 struct type *ret = __propagate_types(prog, c, ok, type, rules);
1625 Interpreting an `exec` doesn't require anything but the `exec`. State
1626 is stored in variables and each variable will be directly linked from
1627 within the `exec` tree. The exception to this is the `main` function
1628 which needs to look at command line arguments. This function will be
1629 interpreted separately.
1631 Each `exec` can return a value combined with a type in `struct lrval`.
1632 The type may be `Tnone` but must be non-NULL. Some `exec`s will return
1633 the location of a value, which can be updated, in `lval`. Others will
1634 set `lval` to NULL indicating that there is a value of appropriate type
1637 ###### core functions
1641 struct value rval, *lval;
1644 static struct lrval _interp_exec(struct parse_context *c, struct exec *e);
1646 static struct value interp_exec(struct parse_context *c, struct exec *e,
1647 struct type **typeret)
1649 struct lrval ret = _interp_exec(c, e);
1651 if (!ret.type) abort();
1653 *typeret = ret.type;
1655 dup_value(ret.type, ret.lval, &ret.rval);
1659 static struct value *linterp_exec(struct parse_context *c, struct exec *e,
1660 struct type **typeret)
1662 struct lrval ret = _interp_exec(c, e);
1665 *typeret = ret.type;
1667 free_value(ret.type, &ret.rval);
1671 static struct lrval _interp_exec(struct parse_context *c, struct exec *e)
1674 struct value rv = {}, *lrv = NULL;
1675 struct type *rvtype;
1677 rvtype = ret.type = Tnone;
1687 struct binode *b = cast(binode, e);
1688 struct value left, right, *lleft;
1689 struct type *ltype, *rtype;
1690 ltype = rtype = Tnone;
1692 ## interp binode cases
1694 free_value(ltype, &left);
1695 free_value(rtype, &right);
1698 ## interp exec cases
1703 ## interp exec cleanup
1709 Now that we have the shape of the interpreter in place we can add some
1710 complex types and connected them in to the data structures and the
1711 different phases of parse, analyse, print, interpret.
1713 Thus far we have arrays and structs.
1717 Arrays can be declared by giving a size and a type, as `[size]type' so
1718 `freq:[26]number` declares `freq` to be an array of 26 numbers. The
1719 size can be either a literal number, or a named constant. Some day an
1720 arbitrary expression will be supported.
1722 As a formal parameter to a function, the array can be declared with a
1723 new variable as the size: `name:[size::number]string`. The `size`
1724 variable is set to the size of the array and must be a constant. As
1725 `number` is the only supported type, it can be left out:
1726 `name:[size::]string`.
1728 Arrays cannot be assigned. When pointers are introduced we will also
1729 introduce array slices which can refer to part or all of an array -
1730 the assignment syntax will create a slice. For now, an array can only
1731 ever be referenced by the name it is declared with. It is likely that
1732 a "`copy`" primitive will eventually be define which can be used to
1733 make a copy of an array with controllable recursive depth.
1735 For now we have two sorts of array, those with fixed size either because
1736 it is given as a literal number or because it is a struct member (which
1737 cannot have a runtime-changing size), and those with a size that is
1738 determined at runtime - local variables with a const size. The former
1739 have their size calculated at parse time, the latter at run time.
1741 For the latter type, the `size` field of the type is the size of a
1742 pointer, and the array is reallocated every time it comes into scope.
1744 We differentiate struct fields with a const size from local variables
1745 with a const size by whether they are prepared at parse time or not.
1747 ###### type union fields
1750 int unspec; // size is unspecified - vsize must be set.
1753 struct variable *vsize;
1754 struct type *member;
1757 ###### value union fields
1758 void *array; // used if not static_size
1760 ###### value functions
1762 static void array_prepare_type(struct parse_context *c, struct type *type,
1765 struct value *vsize;
1767 if (!type->array.vsize || type->array.static_size)
1770 vsize = var_value(c, type->array.vsize);
1772 mpz_tdiv_q(q, mpq_numref(vsize->num), mpq_denref(vsize->num));
1773 type->array.size = mpz_get_si(q);
1777 type->array.static_size = 1;
1778 type->size = type->array.size * type->array.member->size;
1779 type->align = type->array.member->align;
1783 static void array_init(struct type *type, struct value *val)
1786 void *ptr = val->ptr;
1790 if (!type->array.static_size) {
1791 val->array = calloc(type->array.size,
1792 type->array.member->size);
1795 for (i = 0; i < type->array.size; i++) {
1797 v = (void*)ptr + i * type->array.member->size;
1798 val_init(type->array.member, v);
1802 static void array_free(struct type *type, struct value *val)
1805 void *ptr = val->ptr;
1807 if (!type->array.static_size)
1809 for (i = 0; i < type->array.size; i++) {
1811 v = (void*)ptr + i * type->array.member->size;
1812 free_value(type->array.member, v);
1814 if (!type->array.static_size)
1818 static int array_compat(struct type *require, struct type *have)
1820 if (have->compat != require->compat)
1822 /* Both are arrays, so we can look at details */
1823 if (!type_compat(require->array.member, have->array.member, 0))
1825 if (have->array.unspec && require->array.unspec) {
1826 if (have->array.vsize && require->array.vsize &&
1827 have->array.vsize != require->array.vsize) // UNTESTED
1828 /* sizes might not be the same */
1829 return 0; // UNTESTED
1832 if (have->array.unspec || require->array.unspec)
1833 return 1; // UNTESTED
1834 if (require->array.vsize == NULL && have->array.vsize == NULL)
1835 return require->array.size == have->array.size;
1837 return require->array.vsize == have->array.vsize; // UNTESTED
1840 static void array_print_type(struct type *type, FILE *f)
1843 if (type->array.vsize) {
1844 struct binding *b = type->array.vsize->name;
1845 fprintf(f, "%.*s%s]", b->name.len, b->name.txt,
1846 type->array.unspec ? "::" : "");
1848 fprintf(f, "%d]", type->array.size);
1849 type_print(type->array.member, f);
1852 static struct type array_prototype = {
1854 .prepare_type = array_prepare_type,
1855 .print_type = array_print_type,
1856 .compat = array_compat,
1858 .size = sizeof(void*),
1859 .align = sizeof(void*),
1862 ###### declare terminals
1867 | [ NUMBER ] Type ${ {
1870 struct text noname = { "", 0 };
1873 $0 = t = add_type(c, noname, &array_prototype);
1874 t->array.member = $<4;
1875 t->array.vsize = NULL;
1876 if (number_parse(num, tail, $2.txt) == 0)
1877 tok_err(c, "error: unrecognised number", &$2);
1879 tok_err(c, "error: unsupported number suffix", &$2);
1881 t->array.size = mpz_get_ui(mpq_numref(num));
1882 if (mpz_cmp_ui(mpq_denref(num), 1) != 0) {
1883 tok_err(c, "error: array size must be an integer",
1885 } else if (mpz_cmp_ui(mpq_numref(num), 1UL << 30) >= 0)
1886 tok_err(c, "error: array size is too large",
1890 t->array.static_size = 1;
1891 t->size = t->array.size * t->array.member->size;
1892 t->align = t->array.member->align;
1895 | [ IDENTIFIER ] Type ${ {
1896 struct variable *v = var_ref(c, $2.txt);
1897 struct text noname = { "", 0 };
1900 tok_err(c, "error: name undeclared", &$2);
1901 else if (!v->constant)
1902 tok_err(c, "error: array size must be a constant", &$2);
1904 $0 = add_type(c, noname, &array_prototype);
1905 $0->array.member = $<4;
1907 $0->array.vsize = v;
1912 OptType -> Type ${ $0 = $<1; }$
1915 ###### formal type grammar
1917 | [ IDENTIFIER :: OptType ] Type ${ {
1918 struct variable *v = var_decl(c, $ID.txt);
1919 struct text noname = { "", 0 };
1925 $0 = add_type(c, noname, &array_prototype);
1926 $0->array.member = $<6;
1928 $0->array.unspec = 1;
1929 $0->array.vsize = v;
1935 ###### variable grammar
1937 | Variable [ Expression ] ${ {
1938 struct binode *b = new(binode);
1945 ###### print binode cases
1947 print_exec(b->left, -1, bracket);
1949 print_exec(b->right, -1, bracket);
1953 ###### propagate binode cases
1955 /* left must be an array, right must be a number,
1956 * result is the member type of the array
1958 propagate_types(b->right, c, ok, Tnum, 0);
1959 t = propagate_types(b->left, c, ok, NULL, rules & Rnoconstant);
1960 if (!t || t->compat != array_compat) {
1961 type_err(c, "error: %1 cannot be indexed", prog, t, 0, NULL);
1964 if (!type_compat(type, t->array.member, rules)) {
1965 type_err(c, "error: have %1 but need %2", prog,
1966 t->array.member, rules, type);
1968 return t->array.member;
1972 ###### interp binode cases
1978 lleft = linterp_exec(c, b->left, <ype);
1979 right = interp_exec(c, b->right, &rtype);
1981 mpz_tdiv_q(q, mpq_numref(right.num), mpq_denref(right.num));
1985 if (ltype->array.static_size)
1988 ptr = *(void**)lleft;
1989 rvtype = ltype->array.member;
1990 if (i >= 0 && i < ltype->array.size)
1991 lrv = ptr + i * rvtype->size;
1993 val_init(ltype->array.member, &rv);
2000 A `struct` is a data-type that contains one or more other data-types.
2001 It differs from an array in that each member can be of a different
2002 type, and they are accessed by name rather than by number. Thus you
2003 cannot choose an element by calculation, you need to know what you
2006 The language makes no promises about how a given structure will be
2007 stored in memory - it is free to rearrange fields to suit whatever
2008 criteria seems important.
2010 Structs are declared separately from program code - they cannot be
2011 declared in-line in a variable declaration like arrays can. A struct
2012 is given a name and this name is used to identify the type - the name
2013 is not prefixed by the word `struct` as it would be in C.
2015 Structs are only treated as the same if they have the same name.
2016 Simply having the same fields in the same order is not enough. This
2017 might change once we can create structure initializers from a list of
2020 Each component datum is identified much like a variable is declared,
2021 with a name, one or two colons, and a type. The type cannot be omitted
2022 as there is no opportunity to deduce the type from usage. An initial
2023 value can be given following an equals sign, so
2025 ##### Example: a struct type
2031 would declare a type called "complex" which has two number fields,
2032 each initialised to zero.
2034 Struct will need to be declared separately from the code that uses
2035 them, so we will need to be able to print out the declaration of a
2036 struct when reprinting the whole program. So a `print_type_decl` type
2037 function will be needed.
2039 ###### type union fields
2051 ###### type functions
2052 void (*print_type_decl)(struct type *type, FILE *f);
2054 ###### value functions
2056 static void structure_init(struct type *type, struct value *val)
2060 for (i = 0; i < type->structure.nfields; i++) {
2062 v = (void*) val->ptr + type->structure.fields[i].offset;
2063 if (type->structure.fields[i].init)
2064 dup_value(type->structure.fields[i].type,
2065 type->structure.fields[i].init,
2068 val_init(type->structure.fields[i].type, v);
2072 static void structure_free(struct type *type, struct value *val)
2076 for (i = 0; i < type->structure.nfields; i++) {
2078 v = (void*)val->ptr + type->structure.fields[i].offset;
2079 free_value(type->structure.fields[i].type, v);
2083 static void structure_free_type(struct type *t)
2086 for (i = 0; i < t->structure.nfields; i++)
2087 if (t->structure.fields[i].init) {
2088 free_value(t->structure.fields[i].type,
2089 t->structure.fields[i].init);
2091 free(t->structure.fields);
2094 static struct type structure_prototype = {
2095 .init = structure_init,
2096 .free = structure_free,
2097 .free_type = structure_free_type,
2098 .print_type_decl = structure_print_type,
2112 ###### free exec cases
2114 free_exec(cast(fieldref, e)->left);
2118 ###### declare terminals
2121 ###### variable grammar
2123 | Variable . IDENTIFIER ${ {
2124 struct fieldref *fr = new_pos(fieldref, $2);
2131 ###### print exec cases
2135 struct fieldref *f = cast(fieldref, e);
2136 print_exec(f->left, -1, bracket);
2137 printf(".%.*s", f->name.len, f->name.txt);
2141 ###### ast functions
2142 static int find_struct_index(struct type *type, struct text field)
2145 for (i = 0; i < type->structure.nfields; i++)
2146 if (text_cmp(type->structure.fields[i].name, field) == 0)
2151 ###### propagate exec cases
2155 struct fieldref *f = cast(fieldref, prog);
2156 struct type *st = propagate_types(f->left, c, ok, NULL, 0);
2159 type_err(c, "error: unknown type for field access", f->left, // UNTESTED
2161 else if (st->init != structure_init)
2162 type_err(c, "error: field reference attempted on %1, not a struct",
2163 f->left, st, 0, NULL);
2164 else if (f->index == -2) {
2165 f->index = find_struct_index(st, f->name);
2167 type_err(c, "error: cannot find requested field in %1",
2168 f->left, st, 0, NULL);
2170 if (f->index >= 0) {
2171 struct type *ft = st->structure.fields[f->index].type;
2172 if (!type_compat(type, ft, rules))
2173 type_err(c, "error: have %1 but need %2", prog,
2180 ###### interp exec cases
2183 struct fieldref *f = cast(fieldref, e);
2185 struct value *lleft = linterp_exec(c, f->left, <ype);
2186 lrv = (void*)lleft->ptr + ltype->structure.fields[f->index].offset;
2187 rvtype = ltype->structure.fields[f->index].type;
2193 struct fieldlist *prev;
2197 ###### ast functions
2198 static void free_fieldlist(struct fieldlist *f)
2202 free_fieldlist(f->prev);
2204 free_value(f->f.type, f->f.init); // UNTESTED
2205 free(f->f.init); // UNTESTED
2210 ###### top level grammar
2211 DeclareStruct -> struct IDENTIFIER FieldBlock Newlines ${ {
2213 add_type(c, $2.txt, &structure_prototype);
2215 struct fieldlist *f;
2217 for (f = $3; f; f=f->prev)
2220 t->structure.nfields = cnt;
2221 t->structure.fields = calloc(cnt, sizeof(struct field));
2224 int a = f->f.type->align;
2226 t->structure.fields[cnt] = f->f;
2227 if (t->size & (a-1))
2228 t->size = (t->size | (a-1)) + 1;
2229 t->structure.fields[cnt].offset = t->size;
2230 t->size += ((f->f.type->size - 1) | (a-1)) + 1;
2239 FieldBlock -> { IN OptNL FieldLines OUT OptNL } ${ $0 = $<FL; }$
2240 | { SimpleFieldList } ${ $0 = $<SFL; }$
2241 | IN OptNL FieldLines OUT ${ $0 = $<FL; }$
2242 | SimpleFieldList EOL ${ $0 = $<SFL; }$
2244 FieldLines -> SimpleFieldList Newlines ${ $0 = $<SFL; }$
2245 | FieldLines SimpleFieldList Newlines ${
2250 SimpleFieldList -> Field ${ $0 = $<F; }$
2251 | SimpleFieldList ; Field ${
2255 | SimpleFieldList ; ${
2258 | ERROR ${ tok_err(c, "Syntax error in struct field", &$1); }$
2260 Field -> IDENTIFIER : Type = Expression ${ {
2263 $0 = calloc(1, sizeof(struct fieldlist));
2264 $0->f.name = $1.txt;
2269 propagate_types($<5, c, &ok, $3, 0);
2272 c->parse_error = 1; // UNTESTED
2274 struct value vl = interp_exec(c, $5, NULL);
2275 $0->f.init = global_alloc(c, $0->f.type, NULL, &vl);
2278 | IDENTIFIER : Type ${
2279 $0 = calloc(1, sizeof(struct fieldlist));
2280 $0->f.name = $1.txt;
2282 if ($0->f.type->prepare_type)
2283 $0->f.type->prepare_type(c, $0->f.type, 1);
2286 ###### forward decls
2287 static void structure_print_type(struct type *t, FILE *f);
2289 ###### value functions
2290 static void structure_print_type(struct type *t, FILE *f) // UNTESTED
2294 fprintf(f, "struct %.*s\n", t->name.len, t->name.txt);
2296 for (i = 0; i < t->structure.nfields; i++) {
2297 struct field *fl = t->structure.fields + i;
2298 fprintf(f, " %.*s : ", fl->name.len, fl->name.txt);
2299 type_print(fl->type, f);
2300 if (fl->type->print && fl->init) {
2302 if (fl->type == Tstr)
2303 fprintf(f, "\""); // UNTESTED
2304 print_value(fl->type, fl->init);
2305 if (fl->type == Tstr)
2306 fprintf(f, "\""); // UNTESTED
2312 ###### print type decls
2314 struct type *t; // UNTESTED
2317 while (target != 0) {
2319 for (t = context.typelist; t ; t=t->next)
2320 if (t->print_type_decl && !t->check_args) {
2329 t->print_type_decl(t, stdout);
2337 A function is a chunk of code which can be passed parameters and can
2338 return results. Each function has a type which includes the set of
2339 parameters and the return value. As yet these types cannot be declared
2340 separately from the function itself.
2342 The parameters can be specified either in parentheses as a ';' separated
2345 ##### Example: function 1
2347 func main(av:[ac::number]string; env:[envc::number]string)
2350 or as an indented list of one parameter per line (though each line can
2351 be a ';' separated list)
2353 ##### Example: function 2
2356 argv:[argc::number]string
2357 env:[envc::number]string
2361 In the first case a return type can follow the paentheses after a colon,
2362 in the second it is given on a line starting with the word `return`.
2364 ##### Example: functions that return
2366 func add(a:number; b:number): number
2377 For constructing these lists we use a `List` binode, which will be
2378 further detailed when Expression Lists are introduced.
2380 ###### type union fields
2383 struct binode *params;
2384 struct type *return_type;
2388 ###### value union fields
2389 struct exec *function;
2391 ###### type functions
2392 void (*check_args)(struct parse_context *c, int *ok,
2393 struct type *require, struct exec *args);
2395 ###### value functions
2397 static void function_free(struct type *type, struct value *val)
2399 free_exec(val->function);
2400 val->function = NULL;
2403 static int function_compat(struct type *require, struct type *have)
2405 // FIXME can I do anything here yet?
2409 static void function_check_args(struct parse_context *c, int *ok,
2410 struct type *require, struct exec *args)
2412 /* This should be 'compat', but we don't have a 'tuple' type to
2413 * hold the type of 'args'
2415 struct binode *arg = cast(binode, args);
2416 struct binode *param = require->function.params;
2419 struct var *pv = cast(var, param->left);
2421 type_err(c, "error: insufficient arguments to function.",
2422 args, NULL, 0, NULL);
2426 propagate_types(arg->left, c, ok, pv->var->type, 0);
2427 param = cast(binode, param->right);
2428 arg = cast(binode, arg->right);
2431 type_err(c, "error: too many arguments to function.",
2432 args, NULL, 0, NULL);
2435 static void function_print(struct type *type, struct value *val)
2437 print_exec(val->function, 1, 0);
2440 static void function_print_type_decl(struct type *type, FILE *f)
2444 for (b = type->function.params; b; b = cast(binode, b->right)) {
2445 struct variable *v = cast(var, b->left)->var;
2446 fprintf(f, "%.*s%s", v->name->name.len, v->name->name.txt,
2447 v->constant ? "::" : ":");
2448 type_print(v->type, f);
2453 if (type->function.return_type != Tnone) {
2455 type_print(type->function.return_type, f);
2460 static void function_free_type(struct type *t)
2462 free_exec(t->function.params);
2465 static struct type function_prototype = {
2466 .size = sizeof(void*),
2467 .align = sizeof(void*),
2468 .free = function_free,
2469 .compat = function_compat,
2470 .check_args = function_check_args,
2471 .print = function_print,
2472 .print_type_decl = function_print_type_decl,
2473 .free_type = function_free_type,
2476 ###### declare terminals
2486 FuncName -> IDENTIFIER ${ {
2487 struct variable *v = var_decl(c, $1.txt);
2488 struct var *e = new_pos(var, $1);
2494 v = var_ref(c, $1.txt);
2496 type_err(c, "error: function '%v' redeclared",
2498 type_err(c, "info: this is where '%v' was first declared",
2499 v->where_decl, NULL, 0, NULL);
2505 Args -> ArgsLine NEWLINE ${ $0 = $<AL; }$
2506 | Args ArgsLine NEWLINE ${ {
2507 struct binode *b = $<AL;
2508 struct binode **bp = &b;
2510 bp = (struct binode **)&(*bp)->left;
2515 ArgsLine -> ${ $0 = NULL; }$
2516 | Varlist ${ $0 = $<1; }$
2517 | Varlist ; ${ $0 = $<1; }$
2519 Varlist -> Varlist ; ArgDecl ${
2533 ArgDecl -> IDENTIFIER : FormalType ${ {
2534 struct variable *v = var_decl(c, $1.txt);
2540 ## Executables: the elements of code
2542 Each code element needs to be parsed, printed, analysed,
2543 interpreted, and freed. There are several, so let's just start with
2544 the easy ones and work our way up.
2548 We have already met values as separate objects. When manifest
2549 constants appear in the program text, that must result in an executable
2550 which has a constant value. So the `val` structure embeds a value in
2563 ###### ast functions
2564 struct val *new_val(struct type *T, struct token tk)
2566 struct val *v = new_pos(val, tk);
2577 $0 = new_val(Tbool, $1);
2581 $0 = new_val(Tbool, $1);
2585 $0 = new_val(Tnum, $1);
2588 if (number_parse($0->val.num, tail, $1.txt) == 0)
2589 mpq_init($0->val.num); // UNTESTED
2591 tok_err(c, "error: unsupported number suffix",
2596 $0 = new_val(Tstr, $1);
2599 string_parse(&$1, '\\', &$0->val.str, tail);
2601 tok_err(c, "error: unsupported string suffix",
2606 $0 = new_val(Tstr, $1);
2609 string_parse(&$1, '\\', &$0->val.str, tail);
2611 tok_err(c, "error: unsupported string suffix",
2616 ###### print exec cases
2619 struct val *v = cast(val, e);
2620 if (v->vtype == Tstr)
2622 print_value(v->vtype, &v->val);
2623 if (v->vtype == Tstr)
2628 ###### propagate exec cases
2631 struct val *val = cast(val, prog);
2632 if (!type_compat(type, val->vtype, rules))
2633 type_err(c, "error: expected %1%r found %2",
2634 prog, type, rules, val->vtype);
2638 ###### interp exec cases
2640 rvtype = cast(val, e)->vtype;
2641 dup_value(rvtype, &cast(val, e)->val, &rv);
2644 ###### ast functions
2645 static void free_val(struct val *v)
2648 free_value(v->vtype, &v->val);
2652 ###### free exec cases
2653 case Xval: free_val(cast(val, e)); break;
2655 ###### ast functions
2656 // Move all nodes from 'b' to 'rv', reversing their order.
2657 // In 'b' 'left' is a list, and 'right' is the last node.
2658 // In 'rv', left' is the first node and 'right' is a list.
2659 static struct binode *reorder_bilist(struct binode *b)
2661 struct binode *rv = NULL;
2664 struct exec *t = b->right;
2668 b = cast(binode, b->left);
2678 Just as we used a `val` to wrap a value into an `exec`, we similarly
2679 need a `var` to wrap a `variable` into an exec. While each `val`
2680 contained a copy of the value, each `var` holds a link to the variable
2681 because it really is the same variable no matter where it appears.
2682 When a variable is used, we need to remember to follow the `->merged`
2683 link to find the primary instance.
2691 struct variable *var;
2699 VariableDecl -> IDENTIFIER : ${ {
2700 struct variable *v = var_decl(c, $1.txt);
2701 $0 = new_pos(var, $1);
2706 v = var_ref(c, $1.txt);
2708 type_err(c, "error: variable '%v' redeclared",
2710 type_err(c, "info: this is where '%v' was first declared",
2711 v->where_decl, NULL, 0, NULL);
2714 | IDENTIFIER :: ${ {
2715 struct variable *v = var_decl(c, $1.txt);
2716 $0 = new_pos(var, $1);
2722 v = var_ref(c, $1.txt);
2724 type_err(c, "error: variable '%v' redeclared",
2726 type_err(c, "info: this is where '%v' was first declared",
2727 v->where_decl, NULL, 0, NULL);
2730 | IDENTIFIER : Type ${ {
2731 struct variable *v = var_decl(c, $1.txt);
2732 $0 = new_pos(var, $1);
2739 v = var_ref(c, $1.txt);
2741 type_err(c, "error: variable '%v' redeclared",
2743 type_err(c, "info: this is where '%v' was first declared",
2744 v->where_decl, NULL, 0, NULL);
2747 | IDENTIFIER :: Type ${ {
2748 struct variable *v = var_decl(c, $1.txt);
2749 $0 = new_pos(var, $1);
2757 v = var_ref(c, $1.txt);
2759 type_err(c, "error: variable '%v' redeclared",
2761 type_err(c, "info: this is where '%v' was first declared",
2762 v->where_decl, NULL, 0, NULL);
2767 Variable -> IDENTIFIER ${ {
2768 struct variable *v = var_ref(c, $1.txt);
2769 $0 = new_pos(var, $1);
2771 /* This might be a label - allocate a var just in case */
2772 v = var_decl(c, $1.txt);
2779 cast(var, $0)->var = v;
2783 ###### print exec cases
2786 struct var *v = cast(var, e);
2788 struct binding *b = v->var->name;
2789 printf("%.*s", b->name.len, b->name.txt);
2796 if (loc && loc->type == Xvar) {
2797 struct var *v = cast(var, loc);
2799 struct binding *b = v->var->name;
2800 fprintf(stderr, "%.*s", b->name.len, b->name.txt);
2802 fputs("???", stderr); // NOTEST
2804 fputs("NOTVAR", stderr);
2807 ###### propagate exec cases
2811 struct var *var = cast(var, prog);
2812 struct variable *v = var->var;
2814 type_err(c, "%d:BUG: no variable!!", prog, NULL, 0, NULL); // NOTEST
2815 return Tnone; // NOTEST
2818 if (v->constant && (rules & Rnoconstant)) {
2819 type_err(c, "error: Cannot assign to a constant: %v",
2820 prog, NULL, 0, NULL);
2821 type_err(c, "info: name was defined as a constant here",
2822 v->where_decl, NULL, 0, NULL);
2825 if (v->type == Tnone && v->where_decl == prog)
2826 type_err(c, "error: variable used but not declared: %v",
2827 prog, NULL, 0, NULL);
2828 if (v->type == NULL) {
2829 if (type && *ok != 0) {
2831 v->where_set = prog;
2836 if (!type_compat(type, v->type, rules)) {
2837 type_err(c, "error: expected %1%r but variable '%v' is %2", prog,
2838 type, rules, v->type);
2839 type_err(c, "info: this is where '%v' was set to %1", v->where_set,
2840 v->type, rules, NULL);
2847 ###### interp exec cases
2850 struct var *var = cast(var, e);
2851 struct variable *v = var->var;
2854 lrv = var_value(c, v);
2859 ###### ast functions
2861 static void free_var(struct var *v)
2866 ###### free exec cases
2867 case Xvar: free_var(cast(var, e)); break;
2869 ### Expressions: Conditional
2871 Our first user of the `binode` will be conditional expressions, which
2872 is a bit odd as they actually have three components. That will be
2873 handled by having 2 binodes for each expression. The conditional
2874 expression is the lowest precedence operator which is why we define it
2875 first - to start the precedence list.
2877 Conditional expressions are of the form "value `if` condition `else`
2878 other_value". They associate to the right, so everything to the right
2879 of `else` is part of an else value, while only a higher-precedence to
2880 the left of `if` is the if values. Between `if` and `else` there is no
2881 room for ambiguity, so a full conditional expression is allowed in
2893 Expression -> Expression if Expression else Expression $$ifelse ${ {
2894 struct binode *b1 = new(binode);
2895 struct binode *b2 = new(binode);
2904 ## expression grammar
2906 ###### print binode cases
2909 b2 = cast(binode, b->right);
2910 if (bracket) printf("(");
2911 print_exec(b2->left, -1, bracket);
2913 print_exec(b->left, -1, bracket);
2915 print_exec(b2->right, -1, bracket);
2916 if (bracket) printf(")");
2919 ###### propagate binode cases
2922 /* cond must be Tbool, others must match */
2923 struct binode *b2 = cast(binode, b->right);
2926 propagate_types(b->left, c, ok, Tbool, 0);
2927 t = propagate_types(b2->left, c, ok, type, Rnolabel);
2928 t2 = propagate_types(b2->right, c, ok, type ?: t, Rnolabel);
2932 ###### interp binode cases
2935 struct binode *b2 = cast(binode, b->right);
2936 left = interp_exec(c, b->left, <ype);
2938 rv = interp_exec(c, b2->left, &rvtype); // UNTESTED
2940 rv = interp_exec(c, b2->right, &rvtype);
2946 We take a brief detour, now that we have expressions, to describe lists
2947 of expressions. These will be needed for function parameters and
2948 possibly other situations. They seem generic enough to introduce here
2949 to be used elsewhere.
2951 And ExpressionList will use the `List` type of `binode`, building up at
2952 the end. And place where they are used will probably call
2953 `reorder_bilist()` to get a more normal first/next arrangement.
2955 ###### declare terminals
2958 `List` execs have no implicit semantics, so they are never propagated or
2959 interpreted. The can be printed as a comma separate list, which is how
2960 they are parsed. Note they are also used for function formal parameter
2961 lists. In that case a separate function is used to print them.
2963 ###### print binode cases
2967 print_exec(b->left, -1, bracket);
2970 b = cast(binode, b->right);
2974 ###### propagate binode cases
2975 case List: abort(); // NOTEST
2976 ###### interp binode cases
2977 case List: abort(); // NOTEST
2982 ExpressionList -> ExpressionList , Expression ${
2995 ### Expressions: Boolean
2997 The next class of expressions to use the `binode` will be Boolean
2998 expressions. "`and then`" and "`or else`" are similar to `and` and `or`
2999 have same corresponding precendence. The difference is that they don't
3000 evaluate the second expression if not necessary.
3009 ###### expr precedence
3014 ###### expression grammar
3015 | Expression or Expression ${ {
3016 struct binode *b = new(binode);
3022 | Expression or else Expression ${ {
3023 struct binode *b = new(binode);
3030 | Expression and Expression ${ {
3031 struct binode *b = new(binode);
3037 | Expression and then Expression ${ {
3038 struct binode *b = new(binode);
3045 | not Expression ${ {
3046 struct binode *b = new(binode);
3052 ###### print binode cases
3054 if (bracket) printf("(");
3055 print_exec(b->left, -1, bracket);
3057 print_exec(b->right, -1, bracket);
3058 if (bracket) printf(")");
3061 if (bracket) printf("(");
3062 print_exec(b->left, -1, bracket);
3063 printf(" and then ");
3064 print_exec(b->right, -1, bracket);
3065 if (bracket) printf(")");
3068 if (bracket) printf("(");
3069 print_exec(b->left, -1, bracket);
3071 print_exec(b->right, -1, bracket);
3072 if (bracket) printf(")");
3075 if (bracket) printf("(");
3076 print_exec(b->left, -1, bracket);
3077 printf(" or else ");
3078 print_exec(b->right, -1, bracket);
3079 if (bracket) printf(")");
3082 if (bracket) printf("(");
3084 print_exec(b->right, -1, bracket);
3085 if (bracket) printf(")");
3088 ###### propagate binode cases
3094 /* both must be Tbool, result is Tbool */
3095 propagate_types(b->left, c, ok, Tbool, 0);
3096 propagate_types(b->right, c, ok, Tbool, 0);
3097 if (type && type != Tbool)
3098 type_err(c, "error: %1 operation found where %2 expected", prog,
3102 ###### interp binode cases
3104 rv = interp_exec(c, b->left, &rvtype);
3105 right = interp_exec(c, b->right, &rtype);
3106 rv.bool = rv.bool && right.bool;
3109 rv = interp_exec(c, b->left, &rvtype);
3111 rv = interp_exec(c, b->right, NULL);
3114 rv = interp_exec(c, b->left, &rvtype);
3115 right = interp_exec(c, b->right, &rtype);
3116 rv.bool = rv.bool || right.bool;
3119 rv = interp_exec(c, b->left, &rvtype);
3121 rv = interp_exec(c, b->right, NULL);
3124 rv = interp_exec(c, b->right, &rvtype);
3128 ### Expressions: Comparison
3130 Of slightly higher precedence that Boolean expressions are Comparisons.
3131 A comparison takes arguments of any comparable type, but the two types
3134 To simplify the parsing we introduce an `eop` which can record an
3135 expression operator, and the `CMPop` non-terminal will match one of them.
3142 ###### ast functions
3143 static void free_eop(struct eop *e)
3157 ###### expr precedence
3158 $LEFT < > <= >= == != CMPop
3160 ###### expression grammar
3161 | Expression CMPop Expression ${ {
3162 struct binode *b = new(binode);
3172 CMPop -> < ${ $0.op = Less; }$
3173 | > ${ $0.op = Gtr; }$
3174 | <= ${ $0.op = LessEq; }$
3175 | >= ${ $0.op = GtrEq; }$
3176 | == ${ $0.op = Eql; }$
3177 | != ${ $0.op = NEql; }$
3179 ###### print binode cases
3187 if (bracket) printf("(");
3188 print_exec(b->left, -1, bracket);
3190 case Less: printf(" < "); break;
3191 case LessEq: printf(" <= "); break;
3192 case Gtr: printf(" > "); break;
3193 case GtrEq: printf(" >= "); break;
3194 case Eql: printf(" == "); break;
3195 case NEql: printf(" != "); break;
3196 default: abort(); // NOTEST
3198 print_exec(b->right, -1, bracket);
3199 if (bracket) printf(")");
3202 ###### propagate binode cases
3209 /* Both must match but not be labels, result is Tbool */
3210 t = propagate_types(b->left, c, ok, NULL, Rnolabel);
3212 propagate_types(b->right, c, ok, t, 0);
3214 t = propagate_types(b->right, c, ok, NULL, Rnolabel); // UNTESTED
3216 t = propagate_types(b->left, c, ok, t, 0); // UNTESTED
3218 if (!type_compat(type, Tbool, 0))
3219 type_err(c, "error: Comparison returns %1 but %2 expected", prog,
3220 Tbool, rules, type);
3223 ###### interp binode cases
3232 left = interp_exec(c, b->left, <ype);
3233 right = interp_exec(c, b->right, &rtype);
3234 cmp = value_cmp(ltype, rtype, &left, &right);
3237 case Less: rv.bool = cmp < 0; break;
3238 case LessEq: rv.bool = cmp <= 0; break;
3239 case Gtr: rv.bool = cmp > 0; break;
3240 case GtrEq: rv.bool = cmp >= 0; break;
3241 case Eql: rv.bool = cmp == 0; break;
3242 case NEql: rv.bool = cmp != 0; break;
3243 default: rv.bool = 0; break; // NOTEST
3248 ### Expressions: Arithmetic etc.
3250 The remaining expressions with the highest precedence are arithmetic,
3251 string concatenation, and string conversion. String concatenation
3252 (`++`) has the same precedence as multiplication and division, but lower
3255 String conversion is a temporary feature until I get a better type
3256 system. `$` is a prefix operator which expects a string and returns
3259 `+` and `-` are both infix and prefix operations (where they are
3260 absolute value and negation). These have different operator names.
3262 We also have a 'Bracket' operator which records where parentheses were
3263 found. This makes it easy to reproduce these when printing. Possibly I
3264 should only insert brackets were needed for precedence.
3274 ###### expr precedence
3280 ###### expression grammar
3281 | Expression Eop Expression ${ {
3282 struct binode *b = new(binode);
3289 | Expression Top Expression ${ {
3290 struct binode *b = new(binode);
3297 | ( Expression ) ${ {
3298 struct binode *b = new_pos(binode, $1);
3303 | Uop Expression ${ {
3304 struct binode *b = new(binode);
3309 | Value ${ $0 = $<1; }$
3310 | Variable ${ $0 = $<1; }$
3315 Eop -> + ${ $0.op = Plus; }$
3316 | - ${ $0.op = Minus; }$
3318 Uop -> + ${ $0.op = Absolute; }$
3319 | - ${ $0.op = Negate; }$
3320 | $ ${ $0.op = StringConv; }$
3322 Top -> * ${ $0.op = Times; }$
3323 | / ${ $0.op = Divide; }$
3324 | % ${ $0.op = Rem; }$
3325 | ++ ${ $0.op = Concat; }$
3327 ###### print binode cases
3334 if (bracket) printf("(");
3335 print_exec(b->left, indent, bracket);
3337 case Plus: fputs(" + ", stdout); break;
3338 case Minus: fputs(" - ", stdout); break;
3339 case Times: fputs(" * ", stdout); break;
3340 case Divide: fputs(" / ", stdout); break;
3341 case Rem: fputs(" % ", stdout); break;
3342 case Concat: fputs(" ++ ", stdout); break;
3343 default: abort(); // NOTEST
3345 print_exec(b->right, indent, bracket);
3346 if (bracket) printf(")");
3351 if (bracket) printf("(");
3353 case Absolute: fputs("+", stdout); break;
3354 case Negate: fputs("-", stdout); break;
3355 case StringConv: fputs("$", stdout); break;
3356 default: abort(); // NOTEST
3358 print_exec(b->right, indent, bracket);
3359 if (bracket) printf(")");
3363 print_exec(b->right, indent, bracket);
3367 ###### propagate binode cases
3373 /* both must be numbers, result is Tnum */
3376 /* as propagate_types ignores a NULL,
3377 * unary ops fit here too */
3378 propagate_types(b->left, c, ok, Tnum, 0);
3379 propagate_types(b->right, c, ok, Tnum, 0);
3380 if (!type_compat(type, Tnum, 0))
3381 type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
3386 /* both must be Tstr, result is Tstr */
3387 propagate_types(b->left, c, ok, Tstr, 0);
3388 propagate_types(b->right, c, ok, Tstr, 0);
3389 if (!type_compat(type, Tstr, 0))
3390 type_err(c, "error: Concat returns %1 but %2 expected", prog,
3395 /* op must be string, result is number */
3396 propagate_types(b->left, c, ok, Tstr, 0);
3397 if (!type_compat(type, Tnum, 0))
3398 type_err(c, // UNTESTED
3399 "error: Can only convert string to number, not %1",
3400 prog, type, 0, NULL);
3404 return propagate_types(b->right, c, ok, type, 0);
3406 ###### interp binode cases
3409 rv = interp_exec(c, b->left, &rvtype);
3410 right = interp_exec(c, b->right, &rtype);
3411 mpq_add(rv.num, rv.num, right.num);
3414 rv = interp_exec(c, b->left, &rvtype);
3415 right = interp_exec(c, b->right, &rtype);
3416 mpq_sub(rv.num, rv.num, right.num);
3419 rv = interp_exec(c, b->left, &rvtype);
3420 right = interp_exec(c, b->right, &rtype);
3421 mpq_mul(rv.num, rv.num, right.num);
3424 rv = interp_exec(c, b->left, &rvtype);
3425 right = interp_exec(c, b->right, &rtype);
3426 mpq_div(rv.num, rv.num, right.num);
3431 left = interp_exec(c, b->left, <ype);
3432 right = interp_exec(c, b->right, &rtype);
3433 mpz_init(l); mpz_init(r); mpz_init(rem);
3434 mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
3435 mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
3436 mpz_tdiv_r(rem, l, r);
3437 val_init(Tnum, &rv);
3438 mpq_set_z(rv.num, rem);
3439 mpz_clear(r); mpz_clear(l); mpz_clear(rem);
3444 rv = interp_exec(c, b->right, &rvtype);
3445 mpq_neg(rv.num, rv.num);
3448 rv = interp_exec(c, b->right, &rvtype);
3449 mpq_abs(rv.num, rv.num);
3452 rv = interp_exec(c, b->right, &rvtype);
3455 left = interp_exec(c, b->left, <ype);
3456 right = interp_exec(c, b->right, &rtype);
3458 rv.str = text_join(left.str, right.str);
3461 right = interp_exec(c, b->right, &rvtype);
3465 struct text tx = right.str;
3468 if (tx.txt[0] == '-') {
3469 neg = 1; // UNTESTED
3470 tx.txt++; // UNTESTED
3471 tx.len--; // UNTESTED
3473 if (number_parse(rv.num, tail, tx) == 0)
3474 mpq_init(rv.num); // UNTESTED
3476 mpq_neg(rv.num, rv.num); // UNTESTED
3478 printf("Unsupported suffix: %.*s\n", tx.len, tx.txt); // UNTESTED
3482 ###### value functions
3484 static struct text text_join(struct text a, struct text b)
3487 rv.len = a.len + b.len;
3488 rv.txt = malloc(rv.len);
3489 memcpy(rv.txt, a.txt, a.len);
3490 memcpy(rv.txt+a.len, b.txt, b.len);
3496 A function call can appear either as an expression or as a statement.
3497 As functions cannot yet return values, only the statement version will work.
3498 We use a new 'Funcall' binode type to link the function with a list of
3499 arguments, form with the 'List' nodes.
3504 ###### expression grammar
3505 | Variable ( ExpressionList ) ${ {
3506 struct binode *b = new(binode);
3509 b->right = reorder_bilist($<EL);
3513 struct binode *b = new(binode);
3520 ###### SimpleStatement Grammar
3522 | Variable ( ExpressionList ) ${ {
3523 struct binode *b = new(binode);
3526 b->right = reorder_bilist($<EL);
3530 ###### print binode cases
3533 do_indent(indent, "");
3534 print_exec(b->left, -1, bracket);
3536 for (b = cast(binode, b->right); b; b = cast(binode, b->right)) {
3539 print_exec(b->left, -1, bracket);
3549 ###### propagate binode cases
3552 /* Every arg must match formal parameter, and result
3553 * is return type of function
3555 struct binode *args = cast(binode, b->right);
3556 struct var *v = cast(var, b->left);
3558 if (!v->var->type || v->var->type->check_args == NULL) {
3559 type_err(c, "error: attempt to call a non-function.",
3560 prog, NULL, 0, NULL);
3563 v->var->type->check_args(c, ok, v->var->type, args);
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 rv = interp_exec(c, fbody->function, &rvtype);
3593 c->local = oldlocal; c->local_size = old_size;
3598 ### Blocks, Statements, and Statement lists.
3600 Now that we have expressions out of the way we need to turn to
3601 statements. There are simple statements and more complex statements.
3602 Simple statements do not contain (syntactic) newlines, complex statements do.
3604 Statements often come in sequences and we have corresponding simple
3605 statement lists and complex statement lists.
3606 The former comprise only simple statements separated by semicolons.
3607 The later comprise complex statements and simple statement lists. They are
3608 separated by newlines. Thus the semicolon is only used to separate
3609 simple statements on the one line. This may be overly restrictive,
3610 but I'm not sure I ever want a complex statement to share a line with
3613 Note that a simple statement list can still use multiple lines if
3614 subsequent lines are indented, so
3616 ###### Example: wrapped simple statement list
3621 is a single simple statement list. This might allow room for
3622 confusion, so I'm not set on it yet.
3624 A simple statement list needs no extra syntax. A complex statement
3625 list has two syntactic forms. It can be enclosed in braces (much like
3626 C blocks), or it can be introduced by an indent and continue until an
3627 unindented newline (much like Python blocks). With this extra syntax
3628 it is referred to as a block.
3630 Note that a block does not have to include any newlines if it only
3631 contains simple statements. So both of:
3633 if condition: a=b; d=f
3635 if condition { a=b; print f }
3639 In either case the list is constructed from a `binode` list with
3640 `Block` as the operator. When parsing the list it is most convenient
3641 to append to the end, so a list is a list and a statement. When using
3642 the list it is more convenient to consider a list to be a statement
3643 and a list. So we need a function to re-order a list.
3644 `reorder_bilist` serves this purpose.
3646 The only stand-alone statement we introduce at this stage is `pass`
3647 which does nothing and is represented as a `NULL` pointer in a `Block`
3648 list. Other stand-alone statements will follow once the infrastructure
3659 Block -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3660 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3661 | SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3662 | SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3663 | IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3665 OpenBlock -> OpenScope { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3666 | OpenScope { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3667 | OpenScope SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3668 | OpenScope SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3669 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3671 UseBlock -> { OpenScope IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3672 | { OpenScope SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3673 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3675 ColonBlock -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3676 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3677 | : SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3678 | : SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3679 | : IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3681 Statementlist -> ComplexStatements ${ $0 = reorder_bilist($<CS); }$
3683 ComplexStatements -> ComplexStatements ComplexStatement ${
3693 | ComplexStatement ${
3705 ComplexStatement -> SimpleStatements Newlines ${
3706 $0 = reorder_bilist($<SS);
3708 | SimpleStatements ; Newlines ${
3709 $0 = reorder_bilist($<SS);
3711 ## ComplexStatement Grammar
3714 SimpleStatements -> SimpleStatements ; SimpleStatement ${
3720 | SimpleStatement ${
3728 SimpleStatement -> pass ${ $0 = NULL; }$
3729 | ERROR ${ tok_err(c, "Syntax error in statement", &$1); }$
3730 ## SimpleStatement Grammar
3732 ###### print binode cases
3736 if (b->left == NULL) // UNTESTED
3737 printf("pass"); // UNTESTED
3739 print_exec(b->left, indent, bracket); // UNTESTED
3740 if (b->right) { // UNTESTED
3741 printf("; "); // UNTESTED
3742 print_exec(b->right, indent, bracket); // UNTESTED
3745 // block, one per line
3746 if (b->left == NULL)
3747 do_indent(indent, "pass\n");
3749 print_exec(b->left, indent, bracket);
3751 print_exec(b->right, indent, bracket);
3755 ###### propagate binode cases
3758 /* If any statement returns something other than Tnone
3759 * or Tbool then all such must return same type.
3760 * As each statement may be Tnone or something else,
3761 * we must always pass NULL (unknown) down, otherwise an incorrect
3762 * error might occur. We never return Tnone unless it is
3767 for (e = b; e; e = cast(binode, e->right)) {
3768 t = propagate_types(e->left, c, ok, NULL, rules);
3769 if ((rules & Rboolok) && (t == Tbool || t == Tnone))
3771 if (t == Tnone && e->right)
3772 /* Only the final statement *must* return a value
3780 type_err(c, "error: expected %1%r, found %2",
3781 e->left, type, rules, t);
3787 ###### interp binode cases
3789 while (rvtype == Tnone &&
3792 rv = interp_exec(c, b->left, &rvtype);
3793 b = cast(binode, b->right);
3797 ### The Print statement
3799 `print` is a simple statement that takes a comma-separated list of
3800 expressions and prints the values separated by spaces and terminated
3801 by a newline. No control of formatting is possible.
3803 `print` uses `ExpressionList` to collect the expressions and stores them
3804 on the left side of a `Print` binode unlessthere is a trailing comma
3805 when the list is stored on the `right` side and no trailing newline is
3811 ##### expr precedence
3814 ###### SimpleStatement Grammar
3816 | print ExpressionList ${
3820 $0->left = reorder_bilist($<EL);
3822 | print ExpressionList , ${ {
3825 $0->right = reorder_bilist($<EL);
3835 ###### print binode cases
3838 do_indent(indent, "print");
3840 print_exec(b->right, -1, bracket);
3843 print_exec(b->left, -1, bracket);
3848 ###### propagate binode cases
3851 /* don't care but all must be consistent */
3853 b = cast(binode, b->left);
3855 b = cast(binode, b->right);
3857 propagate_types(b->left, c, ok, NULL, Rnolabel);
3858 b = cast(binode, b->right);
3862 ###### interp binode cases
3866 struct binode *b2 = cast(binode, b->left);
3868 b2 = cast(binode, b->right);
3869 for (; b2; b2 = cast(binode, b2->right)) {
3870 left = interp_exec(c, b2->left, <ype);
3871 print_value(ltype, &left);
3872 free_value(ltype, &left);
3876 if (b->right == NULL)
3882 ###### Assignment statement
3884 An assignment will assign a value to a variable, providing it hasn't
3885 been declared as a constant. The analysis phase ensures that the type
3886 will be correct so the interpreter just needs to perform the
3887 calculation. There is a form of assignment which declares a new
3888 variable as well as assigning a value. If a name is assigned before
3889 it is declared, and error will be raised as the name is created as
3890 `Tlabel` and it is illegal to assign to such names.
3896 ###### declare terminals
3899 ###### SimpleStatement Grammar
3900 | Variable = Expression ${
3906 | VariableDecl = Expression ${
3914 if ($1->var->where_set == NULL) {
3916 "Variable declared with no type or value: %v",
3926 ###### print binode cases
3929 do_indent(indent, "");
3930 print_exec(b->left, indent, bracket);
3932 print_exec(b->right, indent, bracket);
3939 struct variable *v = cast(var, b->left)->var;
3940 do_indent(indent, "");
3941 print_exec(b->left, indent, bracket);
3942 if (cast(var, b->left)->var->constant) {
3944 if (v->where_decl == v->where_set) {
3945 type_print(v->type, stdout);
3950 if (v->where_decl == v->where_set) {
3951 type_print(v->type, stdout);
3957 print_exec(b->right, indent, bracket);
3964 ###### propagate binode cases
3968 /* Both must match and not be labels,
3969 * Type must support 'dup',
3970 * For Assign, left must not be constant.
3973 t = propagate_types(b->left, c, ok, NULL,
3974 Rnolabel | (b->op == Assign ? Rnoconstant : 0));
3979 if (propagate_types(b->right, c, ok, t, 0) != t)
3980 if (b->left->type == Xvar)
3981 type_err(c, "info: variable '%v' was set as %1 here.",
3982 cast(var, b->left)->var->where_set, t, rules, NULL);
3984 t = propagate_types(b->right, c, ok, NULL, Rnolabel);
3986 propagate_types(b->left, c, ok, t,
3987 (b->op == Assign ? Rnoconstant : 0));
3989 if (t && t->dup == NULL)
3990 type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
3995 ###### interp binode cases
3998 lleft = linterp_exec(c, b->left, <ype);
3999 right = interp_exec(c, b->right, &rtype);
4001 free_value(ltype, lleft);
4002 dup_value(ltype, &right, lleft);
4009 struct variable *v = cast(var, b->left)->var;
4012 val = var_value(c, v);
4013 if (v->type->prepare_type)
4014 v->type->prepare_type(c, v->type, 0);
4016 right = interp_exec(c, b->right, &rtype);
4017 memcpy(val, &right, rtype->size);
4020 val_init(v->type, val);
4025 ### The `use` statement
4027 The `use` statement is the last "simple" statement. It is needed when a
4028 statement block can return a value. This includes the body of a
4029 function which has a return type, and the "condition" code blocks in
4030 `if`, `while`, and `switch` statements.
4035 ###### expr precedence
4038 ###### SimpleStatement Grammar
4040 $0 = new_pos(binode, $1);
4043 if ($0->right->type == Xvar) {
4044 struct var *v = cast(var, $0->right);
4045 if (v->var->type == Tnone) {
4046 /* Convert this to a label */
4049 v->var->type = Tlabel;
4050 val = global_alloc(c, Tlabel, v->var, NULL);
4056 ###### print binode cases
4059 do_indent(indent, "use ");
4060 print_exec(b->right, -1, bracket);
4065 ###### propagate binode cases
4068 /* result matches value */
4069 return propagate_types(b->right, c, ok, type, 0);
4071 ###### interp binode cases
4074 rv = interp_exec(c, b->right, &rvtype);
4077 ### The Conditional Statement
4079 This is the biggy and currently the only complex statement. This
4080 subsumes `if`, `while`, `do/while`, `switch`, and some parts of `for`.
4081 It is comprised of a number of parts, all of which are optional though
4082 set combinations apply. Each part is (usually) a key word (`then` is
4083 sometimes optional) followed by either an expression or a code block,
4084 except the `casepart` which is a "key word and an expression" followed
4085 by a code block. The code-block option is valid for all parts and,
4086 where an expression is also allowed, the code block can use the `use`
4087 statement to report a value. If the code block does not report a value
4088 the effect is similar to reporting `True`.
4090 The `else` and `case` parts, as well as `then` when combined with
4091 `if`, can contain a `use` statement which will apply to some
4092 containing conditional statement. `for` parts, `do` parts and `then`
4093 parts used with `for` can never contain a `use`, except in some
4094 subordinate conditional statement.
4096 If there is a `forpart`, it is executed first, only once.
4097 If there is a `dopart`, then it is executed repeatedly providing
4098 always that the `condpart` or `cond`, if present, does not return a non-True
4099 value. `condpart` can fail to return any value if it simply executes
4100 to completion. This is treated the same as returning `True`.
4102 If there is a `thenpart` it will be executed whenever the `condpart`
4103 or `cond` returns True (or does not return any value), but this will happen
4104 *after* `dopart` (when present).
4106 If `elsepart` is present it will be executed at most once when the
4107 condition returns `False` or some value that isn't `True` and isn't
4108 matched by any `casepart`. If there are any `casepart`s, they will be
4109 executed when the condition returns a matching value.
4111 The particular sorts of values allowed in case parts has not yet been
4112 determined in the language design, so nothing is prohibited.
4114 The various blocks in this complex statement potentially provide scope
4115 for variables as described earlier. Each such block must include the
4116 "OpenScope" nonterminal before parsing the block, and must call
4117 `var_block_close()` when closing the block.
4119 The code following "`if`", "`switch`" and "`for`" does not get its own
4120 scope, but is in a scope covering the whole statement, so names
4121 declared there cannot be redeclared elsewhere. Similarly the
4122 condition following "`while`" is in a scope the covers the body
4123 ("`do`" part) of the loop, and which does not allow conditional scope
4124 extension. Code following "`then`" (both looping and non-looping),
4125 "`else`" and "`case`" each get their own local scope.
4127 The type requirements on the code block in a `whilepart` are quite
4128 unusal. It is allowed to return a value of some identifiable type, in
4129 which case the loop aborts and an appropriate `casepart` is run, or it
4130 can return a Boolean, in which case the loop either continues to the
4131 `dopart` (on `True`) or aborts and runs the `elsepart` (on `False`).
4132 This is different both from the `ifpart` code block which is expected to
4133 return a Boolean, or the `switchpart` code block which is expected to
4134 return the same type as the casepart values. The correct analysis of
4135 the type of the `whilepart` code block is the reason for the
4136 `Rboolok` flag which is passed to `propagate_types()`.
4138 The `cond_statement` cannot fit into a `binode` so a new `exec` is
4139 defined. As there are two scopes which cover multiple parts - one for
4140 the whole statement and one for "while" and "do" - and as we will use
4141 the 'struct exec' to track scopes, we actually need two new types of
4142 exec. One is a `binode` for the looping part, the rest is the
4143 `cond_statement`. The `cond_statement` will use an auxilliary `struct
4144 casepart` to track a list of case parts.
4155 struct exec *action;
4156 struct casepart *next;
4158 struct cond_statement {
4160 struct exec *forpart, *condpart, *thenpart, *elsepart;
4161 struct binode *looppart;
4162 struct casepart *casepart;
4165 ###### ast functions
4167 static void free_casepart(struct casepart *cp)
4171 free_exec(cp->value);
4172 free_exec(cp->action);
4179 static void free_cond_statement(struct cond_statement *s)
4183 free_exec(s->forpart);
4184 free_exec(s->condpart);
4185 free_exec(s->looppart);
4186 free_exec(s->thenpart);
4187 free_exec(s->elsepart);
4188 free_casepart(s->casepart);
4192 ###### free exec cases
4193 case Xcond_statement: free_cond_statement(cast(cond_statement, e)); break;
4195 ###### ComplexStatement Grammar
4196 | CondStatement ${ $0 = $<1; }$
4198 ###### expr precedence
4199 $TERM for then while do
4206 // A CondStatement must end with EOL, as does CondSuffix and
4208 // ForPart, ThenPart, SwitchPart, CasePart are non-empty and
4209 // may or may not end with EOL
4210 // WhilePart and IfPart include an appropriate Suffix
4212 // ForPart, SwitchPart, and IfPart open scopes, o we have to close
4213 // them. WhilePart opens and closes its own scope.
4214 CondStatement -> ForPart OptNL ThenPart OptNL WhilePart CondSuffix ${
4217 $0->thenpart = $<TP;
4218 $0->looppart = $<WP;
4219 var_block_close(c, CloseSequential, $0);
4221 | ForPart OptNL WhilePart CondSuffix ${
4224 $0->looppart = $<WP;
4225 var_block_close(c, CloseSequential, $0);
4227 | WhilePart CondSuffix ${
4229 $0->looppart = $<WP;
4231 | SwitchPart OptNL CasePart CondSuffix ${
4233 $0->condpart = $<SP;
4234 $CP->next = $0->casepart;
4235 $0->casepart = $<CP;
4236 var_block_close(c, CloseSequential, $0);
4238 | SwitchPart : IN OptNL CasePart CondSuffix OUT Newlines ${
4240 $0->condpart = $<SP;
4241 $CP->next = $0->casepart;
4242 $0->casepart = $<CP;
4243 var_block_close(c, CloseSequential, $0);
4245 | IfPart IfSuffix ${
4247 $0->condpart = $IP.condpart; $IP.condpart = NULL;
4248 $0->thenpart = $IP.thenpart; $IP.thenpart = NULL;
4249 // This is where we close an "if" statement
4250 var_block_close(c, CloseSequential, $0);
4253 CondSuffix -> IfSuffix ${
4256 | Newlines CasePart CondSuffix ${
4258 $CP->next = $0->casepart;
4259 $0->casepart = $<CP;
4261 | CasePart CondSuffix ${
4263 $CP->next = $0->casepart;
4264 $0->casepart = $<CP;
4267 IfSuffix -> Newlines ${ $0 = new(cond_statement); }$
4268 | Newlines ElsePart ${ $0 = $<EP; }$
4269 | ElsePart ${$0 = $<EP; }$
4271 ElsePart -> else OpenBlock Newlines ${
4272 $0 = new(cond_statement);
4273 $0->elsepart = $<OB;
4274 var_block_close(c, CloseElse, $0->elsepart);
4276 | else OpenScope CondStatement ${
4277 $0 = new(cond_statement);
4278 $0->elsepart = $<CS;
4279 var_block_close(c, CloseElse, $0->elsepart);
4283 CasePart -> case Expression OpenScope ColonBlock ${
4284 $0 = calloc(1,sizeof(struct casepart));
4287 var_block_close(c, CloseParallel, $0->action);
4291 // These scopes are closed in CondStatement
4292 ForPart -> for OpenBlock ${
4296 ThenPart -> then OpenBlock ${
4298 var_block_close(c, CloseSequential, $0);
4302 // This scope is closed in CondStatement
4303 WhilePart -> while UseBlock OptNL do OpenBlock ${
4308 var_block_close(c, CloseSequential, $0->right);
4309 var_block_close(c, CloseSequential, $0);
4311 | while OpenScope Expression OpenScope ColonBlock ${
4316 var_block_close(c, CloseSequential, $0->right);
4317 var_block_close(c, CloseSequential, $0);
4321 IfPart -> if UseBlock OptNL then OpenBlock ${
4324 var_block_close(c, CloseParallel, $0.thenpart);
4326 | if OpenScope Expression OpenScope ColonBlock ${
4329 var_block_close(c, CloseParallel, $0.thenpart);
4331 | if OpenScope Expression OpenScope OptNL then Block ${
4334 var_block_close(c, CloseParallel, $0.thenpart);
4338 // This scope is closed in CondStatement
4339 SwitchPart -> switch OpenScope Expression ${
4342 | switch UseBlock ${
4346 ###### print binode cases
4348 if (b->left && b->left->type == Xbinode &&
4349 cast(binode, b->left)->op == Block) {
4351 do_indent(indent, "while {\n");
4353 do_indent(indent, "while\n");
4354 print_exec(b->left, indent+1, bracket);
4356 do_indent(indent, "} do {\n");
4358 do_indent(indent, "do\n");
4359 print_exec(b->right, indent+1, bracket);
4361 do_indent(indent, "}\n");
4363 do_indent(indent, "while ");
4364 print_exec(b->left, 0, bracket);
4369 print_exec(b->right, indent+1, bracket);
4371 do_indent(indent, "}\n");
4375 ###### print exec cases
4377 case Xcond_statement:
4379 struct cond_statement *cs = cast(cond_statement, e);
4380 struct casepart *cp;
4382 do_indent(indent, "for");
4383 if (bracket) printf(" {\n"); else printf("\n");
4384 print_exec(cs->forpart, indent+1, bracket);
4387 do_indent(indent, "} then {\n");
4389 do_indent(indent, "then\n");
4390 print_exec(cs->thenpart, indent+1, bracket);
4392 if (bracket) do_indent(indent, "}\n");
4395 print_exec(cs->looppart, indent, bracket);
4399 do_indent(indent, "switch");
4401 do_indent(indent, "if");
4402 if (cs->condpart && cs->condpart->type == Xbinode &&
4403 cast(binode, cs->condpart)->op == Block) {
4408 print_exec(cs->condpart, indent+1, bracket);
4410 do_indent(indent, "}\n");
4412 do_indent(indent, "then\n");
4413 print_exec(cs->thenpart, indent+1, bracket);
4417 print_exec(cs->condpart, 0, bracket);
4423 print_exec(cs->thenpart, indent+1, bracket);
4425 do_indent(indent, "}\n");
4430 for (cp = cs->casepart; cp; cp = cp->next) {
4431 do_indent(indent, "case ");
4432 print_exec(cp->value, -1, 0);
4437 print_exec(cp->action, indent+1, bracket);
4439 do_indent(indent, "}\n");
4442 do_indent(indent, "else");
4447 print_exec(cs->elsepart, indent+1, bracket);
4449 do_indent(indent, "}\n");
4454 ###### propagate binode cases
4456 t = propagate_types(b->right, c, ok, Tnone, 0);
4457 if (!type_compat(Tnone, t, 0))
4458 *ok = 0; // UNTESTED
4459 return propagate_types(b->left, c, ok, type, rules);
4461 ###### propagate exec cases
4462 case Xcond_statement:
4464 // forpart and looppart->right must return Tnone
4465 // thenpart must return Tnone if there is a loopart,
4466 // otherwise it is like elsepart.
4468 // be bool if there is no casepart
4469 // match casepart->values if there is a switchpart
4470 // either be bool or match casepart->value if there
4472 // elsepart and casepart->action must match the return type
4473 // expected of this statement.
4474 struct cond_statement *cs = cast(cond_statement, prog);
4475 struct casepart *cp;
4477 t = propagate_types(cs->forpart, c, ok, Tnone, 0);
4478 if (!type_compat(Tnone, t, 0))
4479 *ok = 0; // UNTESTED
4482 t = propagate_types(cs->thenpart, c, ok, Tnone, 0);
4483 if (!type_compat(Tnone, t, 0))
4484 *ok = 0; // UNTESTED
4486 if (cs->casepart == NULL) {
4487 propagate_types(cs->condpart, c, ok, Tbool, 0);
4488 propagate_types(cs->looppart, c, ok, Tbool, 0);
4490 /* Condpart must match case values, with bool permitted */
4492 for (cp = cs->casepart;
4493 cp && !t; cp = cp->next)
4494 t = propagate_types(cp->value, c, ok, NULL, 0);
4495 if (!t && cs->condpart)
4496 t = propagate_types(cs->condpart, c, ok, NULL, Rboolok); // UNTESTED
4497 if (!t && cs->looppart)
4498 t = propagate_types(cs->looppart, c, ok, NULL, Rboolok); // UNTESTED
4499 // Now we have a type (I hope) push it down
4501 for (cp = cs->casepart; cp; cp = cp->next)
4502 propagate_types(cp->value, c, ok, t, 0);
4503 propagate_types(cs->condpart, c, ok, t, Rboolok);
4504 propagate_types(cs->looppart, c, ok, t, Rboolok);
4507 // (if)then, else, and case parts must return expected type.
4508 if (!cs->looppart && !type)
4509 type = propagate_types(cs->thenpart, c, ok, NULL, rules);
4511 type = propagate_types(cs->elsepart, c, ok, NULL, rules);
4512 for (cp = cs->casepart;
4514 cp = cp->next) // UNTESTED
4515 type = propagate_types(cp->action, c, ok, NULL, rules); // UNTESTED
4518 propagate_types(cs->thenpart, c, ok, type, rules);
4519 propagate_types(cs->elsepart, c, ok, type, rules);
4520 for (cp = cs->casepart; cp ; cp = cp->next)
4521 propagate_types(cp->action, c, ok, type, rules);
4527 ###### interp binode cases
4529 // This just performs one iterration of the loop
4530 rv = interp_exec(c, b->left, &rvtype);
4531 if (rvtype == Tnone ||
4532 (rvtype == Tbool && rv.bool != 0))
4533 // cnd is Tnone or Tbool, doesn't need to be freed
4534 interp_exec(c, b->right, NULL);
4537 ###### interp exec cases
4538 case Xcond_statement:
4540 struct value v, cnd;
4541 struct type *vtype, *cndtype;
4542 struct casepart *cp;
4543 struct cond_statement *cs = cast(cond_statement, e);
4546 interp_exec(c, cs->forpart, NULL);
4548 while ((cnd = interp_exec(c, cs->looppart, &cndtype)),
4549 cndtype == Tnone || (cndtype == Tbool && cnd.bool != 0))
4550 interp_exec(c, cs->thenpart, NULL);
4552 cnd = interp_exec(c, cs->condpart, &cndtype);
4553 if ((cndtype == Tnone ||
4554 (cndtype == Tbool && cnd.bool != 0))) {
4555 // cnd is Tnone or Tbool, doesn't need to be freed
4556 rv = interp_exec(c, cs->thenpart, &rvtype);
4557 // skip else (and cases)
4561 for (cp = cs->casepart; cp; cp = cp->next) {
4562 v = interp_exec(c, cp->value, &vtype);
4563 if (value_cmp(cndtype, vtype, &v, &cnd) == 0) {
4564 free_value(vtype, &v);
4565 free_value(cndtype, &cnd);
4566 rv = interp_exec(c, cp->action, &rvtype);
4569 free_value(vtype, &v);
4571 free_value(cndtype, &cnd);
4573 rv = interp_exec(c, cs->elsepart, &rvtype);
4580 ### Top level structure
4582 All the language elements so far can be used in various places. Now
4583 it is time to clarify what those places are.
4585 At the top level of a file there will be a number of declarations.
4586 Many of the things that can be declared haven't been described yet,
4587 such as functions, procedures, imports, and probably more.
4588 For now there are two sorts of things that can appear at the top
4589 level. They are predefined constants, `struct` types, and the `main`
4590 function. While the syntax will allow the `main` function to appear
4591 multiple times, that will trigger an error if it is actually attempted.
4593 The various declarations do not return anything. They store the
4594 various declarations in the parse context.
4596 ###### Parser: grammar
4599 Ocean -> OptNL DeclarationList
4601 ## declare terminals
4608 DeclarationList -> Declaration
4609 | DeclarationList Declaration
4611 Declaration -> ERROR Newlines ${
4612 tok_err(c, // UNTESTED
4613 "error: unhandled parse error", &$1);
4619 ## top level grammar
4623 ### The `const` section
4625 As well as being defined in with the code that uses them, constants
4626 can be declared at the top level. These have full-file scope, so they
4627 are always `InScope`. The value of a top level constant can be given
4628 as an expression, and this is evaluated immediately rather than in the
4629 later interpretation stage. Once we add functions to the language, we
4630 will need rules concern which, if any, can be used to define a top
4633 Constants are defined in a section that starts with the reserved word
4634 `const` and then has a block with a list of assignment statements.
4635 For syntactic consistency, these must use the double-colon syntax to
4636 make it clear that they are constants. Type can also be given: if
4637 not, the type will be determined during analysis, as with other
4640 As the types constants are inserted at the head of a list, printing
4641 them in the same order that they were read is not straight forward.
4642 We take a quadratic approach here and count the number of constants
4643 (variables of depth 0), then count down from there, each time
4644 searching through for the Nth constant for decreasing N.
4646 ###### top level grammar
4650 DeclareConstant -> const { IN OptNL ConstList OUT OptNL } Newlines
4651 | const { SimpleConstList } Newlines
4652 | const IN OptNL ConstList OUT Newlines
4653 | const SimpleConstList Newlines
4655 ConstList -> ConstList SimpleConstLine
4657 SimpleConstList -> SimpleConstList ; Const
4660 SimpleConstLine -> SimpleConstList Newlines
4661 | ERROR Newlines ${ tok_err(c, "Syntax error in constant", &$1); }$
4664 CType -> Type ${ $0 = $<1; }$
4667 Const -> IDENTIFIER :: CType = Expression ${ {
4671 v = var_decl(c, $1.txt);
4673 struct var *var = new_pos(var, $1);
4674 v->where_decl = var;
4679 v = var_ref(c, $1.txt);
4680 tok_err(c, "error: name already declared", &$1);
4681 type_err(c, "info: this is where '%v' was first declared",
4682 v->where_decl, NULL, 0, NULL);
4686 propagate_types($5, c, &ok, $3, 0);
4691 struct value res = interp_exec(c, $5, &v->type);
4692 global_alloc(c, v->type, v, &res);
4696 ###### print const decls
4701 while (target != 0) {
4703 for (v = context.in_scope; v; v=v->in_scope)
4704 if (v->depth == 0 && v->constant) {
4715 struct value *val = var_value(&context, v);
4716 printf(" %.*s :: ", v->name->name.len, v->name->name.txt);
4717 type_print(v->type, stdout);
4719 if (v->type == Tstr)
4721 print_value(v->type, val);
4722 if (v->type == Tstr)
4730 ### Function declarations
4732 The code in an Ocean program is all stored in function declarations.
4733 One of the functions must be named `main` and it must accept an array of
4734 strings as a parameter - the command line arguments.
4736 As this is the top level, several things are handled a bit differently.
4737 The function is not interpreted by `interp_exec` as that isn't passed
4738 the argument list which the program requires. Similarly type analysis
4739 is a bit more interesting at this level.
4741 ###### ast functions
4743 static struct variable *declare_function(struct parse_context *c,
4744 struct variable *name,
4745 struct binode *args,
4749 struct text funcname = {" func", 5};
4751 struct value fn = {.function = code};
4752 name->type = add_type(c, funcname, &function_prototype);
4753 name->type->function.params = reorder_bilist(args);
4754 name->type->function.return_type = ret;
4755 global_alloc(c, name->type, name, &fn);
4756 var_block_close(c, CloseSequential, code);
4758 var_block_close(c, CloseSequential, NULL);
4762 ###### declare terminals
4765 ###### top level grammar
4768 DeclareFunction -> func FuncName ( OpenScope ArgsLine ) Block Newlines ${
4769 $0 = declare_function(c, $<FN, $<Ar, Tnone, $<Bl);
4771 | func FuncName IN OpenScope Args OUT OptNL do Block Newlines ${
4772 $0 = declare_function(c, $<FN, $<Ar, Tnone, $<Bl);
4774 | func FuncName NEWLINE OpenScope OptNL do Block Newlines ${
4775 $0 = declare_function(c, $<FN, NULL, Tnone, $<Bl);
4777 | func FuncName ( OpenScope ArgsLine ) : Type Block Newlines ${
4778 $0 = declare_function(c, $<FN, $<Ar, $<Ty, $<Bl);
4780 | func FuncName IN OpenScope Args OUT OptNL return Type Newlines do Block Newlines ${
4781 $0 = declare_function(c, $<FN, $<Ar, $<Ty, $<Bl);
4783 | func FuncName NEWLINE OpenScope return Type Newlines do Block Newlines ${
4784 $0 = declare_function(c, $<FN, NULL, $<Ty, $<Bl);
4787 ###### print func decls
4792 while (target != 0) {
4794 for (v = context.in_scope; v; v=v->in_scope)
4795 if (v->depth == 0 && v->type && v->type->check_args) {
4804 struct value *val = var_value(&context, v);
4805 printf("func %.*s", v->name->name.len, v->name->name.txt);
4806 v->type->print_type_decl(v->type, stdout);
4808 print_exec(val->function, 0, brackets);
4810 print_value(v->type, val);
4811 printf("/* frame size %d */\n", v->type->function.local_size);
4817 ###### core functions
4819 static int analyse_funcs(struct parse_context *c)
4823 for (v = c->in_scope; v; v = v->in_scope) {
4826 if (v->depth != 0 || !v->type || !v->type->check_args)
4828 val = var_value(c, v);
4831 propagate_types(val->function, c, &ok,
4832 v->type->function.return_type, 0);
4835 /* Make sure everything is still consistent */
4836 propagate_types(val->function, c, &ok,
4837 v->type->function.return_type, 0);
4840 v->type->function.local_size = scope_finalize(c);
4845 static int analyse_main(struct type *type, struct parse_context *c)
4847 struct binode *bp = type->function.params;
4851 struct type *argv_type;
4852 struct text argv_type_name = { " argv", 5 };
4854 argv_type = add_type(c, argv_type_name, &array_prototype);
4855 argv_type->array.member = Tstr;
4856 argv_type->array.unspec = 1;
4858 for (b = bp; b; b = cast(binode, b->right)) {
4862 propagate_types(b->left, c, &ok, argv_type, 0);
4864 default: /* invalid */ // NOTEST
4865 propagate_types(b->left, c, &ok, Tnone, 0); // NOTEST
4871 return !c->parse_error;
4874 static void interp_main(struct parse_context *c, int argc, char **argv)
4876 struct value *progp = NULL;
4877 struct text main_name = { "main", 4 };
4878 struct variable *mainv;
4884 mainv = var_ref(c, main_name);
4886 progp = var_value(c, mainv);
4887 if (!progp || !progp->function) {
4888 fprintf(stderr, "oceani: no main function found.\n");
4892 if (!analyse_main(mainv->type, c)) {
4893 fprintf(stderr, "oceani: main has wrong type.\n");
4897 al = mainv->type->function.params;
4899 c->local_size = mainv->type->function.local_size;
4900 c->local = calloc(1, c->local_size);
4902 struct var *v = cast(var, al->left);
4903 struct value *vl = var_value(c, v->var);
4913 mpq_set_ui(argcq, argc, 1);
4914 memcpy(var_value(c, t->array.vsize), &argcq, sizeof(argcq));
4915 t->prepare_type(c, t, 0);
4916 array_init(v->var->type, vl);
4917 for (i = 0; i < argc; i++) {
4918 struct value *vl2 = vl->array + i * v->var->type->array.member->size;
4920 arg.str.txt = argv[i];
4921 arg.str.len = strlen(argv[i]);
4922 free_value(Tstr, vl2);
4923 dup_value(Tstr, &arg, vl2);
4927 al = cast(binode, al->right);
4929 v = interp_exec(c, progp->function, &vtype);
4930 free_value(vtype, &v);
4935 ###### ast functions
4936 void free_variable(struct variable *v)
4940 ## And now to test it out.
4942 Having a language requires having a "hello world" program. I'll
4943 provide a little more than that: a program that prints "Hello world"
4944 finds the GCD of two numbers, prints the first few elements of
4945 Fibonacci, performs a binary search for a number, and a few other
4946 things which will likely grow as the languages grows.
4948 ###### File: oceani.mk
4951 @echo "===== DEMO ====="
4952 ./oceani --section "demo: hello" oceani.mdc 55 33
4958 four ::= 2 + 2 ; five ::= 10/2
4959 const pie ::= "I like Pie";
4960 cake ::= "The cake is"
4968 func main(argv:[argc::]string)
4969 print "Hello World, what lovely oceans you have!"
4970 print "Are there", five, "?"
4971 print pi, pie, "but", cake
4973 A := $argv[1]; B := $argv[2]
4975 /* When a variable is defined in both branches of an 'if',
4976 * and used afterwards, the variables are merged.
4982 print "Is", A, "bigger than", B,"? ", bigger
4983 /* If a variable is not used after the 'if', no
4984 * merge happens, so types can be different
4987 double:string = "yes"
4988 print A, "is more than twice", B, "?", double
4991 print "double", B, "is", double
4996 if a > 0 and then b > 0:
5002 print "GCD of", A, "and", B,"is", a
5004 print a, "is not positive, cannot calculate GCD"
5006 print b, "is not positive, cannot calculate GCD"
5011 print "Fibonacci:", f1,f2,
5012 then togo = togo - 1
5020 /* Binary search... */
5025 mid := (lo + hi) / 2
5038 print "Yay, I found", target
5040 print "Closest I found was", lo
5045 // "middle square" PRNG. Not particularly good, but one my
5046 // Dad taught me - the first one I ever heard of.
5047 for i:=1; then i = i + 1; while i < size:
5048 n := list[i-1] * list[i-1]
5049 list[i] = (n / 100) % 10 000
5051 print "Before sort:",
5052 for i:=0; then i = i + 1; while i < size:
5056 for i := 1; then i=i+1; while i < size:
5057 for j:=i-1; then j=j-1; while j >= 0:
5058 if list[j] > list[j+1]:
5062 print " After sort:",
5063 for i:=0; then i = i + 1; while i < size:
5067 if 1 == 2 then print "yes"; else print "no"
5071 bob.alive = (bob.name == "Hello")
5072 print "bob", "is" if bob.alive else "isn't", "alive"