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 (though results are not yet implemented). Each function
2339 has a type which includes the set of parameters and the return value.
2340 As yet these types cannot be declared separately from the function
2343 The parameters can be specified either in parentheses as a ';' separated
2346 ##### Example: function 1
2348 func main(av:[ac::number]string; env:[envc::number]string)
2351 or as an indented list of one parameter per line (though each line can
2352 be a ';' separated list)
2354 ##### Example: function 2
2357 argv:[argc::number]string
2358 env:[envc::number]string
2362 For constructing these lists we use a `List` binode, which will be
2363 further detailed when Expression Lists are introduced.
2365 ###### type union fields
2368 struct binode *params;
2372 ###### value union fields
2373 struct exec *function;
2375 ###### type functions
2376 void (*check_args)(struct parse_context *c, int *ok,
2377 struct type *require, struct exec *args);
2379 ###### value functions
2381 static void function_free(struct type *type, struct value *val)
2383 free_exec(val->function);
2384 val->function = NULL;
2387 static int function_compat(struct type *require, struct type *have)
2389 // FIXME can I do anything here yet?
2393 static void function_check_args(struct parse_context *c, int *ok,
2394 struct type *require, struct exec *args)
2396 /* This should be 'compat', but we don't have a 'tuple' type to
2397 * hold the type of 'args'
2399 struct binode *arg = cast(binode, args);
2400 struct binode *param = require->function.params;
2403 struct var *pv = cast(var, param->left);
2405 type_err(c, "error: insufficient arguments to function.",
2406 args, NULL, 0, NULL);
2410 propagate_types(arg->left, c, ok, pv->var->type, 0);
2411 param = cast(binode, param->right);
2412 arg = cast(binode, arg->right);
2415 type_err(c, "error: too many arguments to function.",
2416 args, NULL, 0, NULL);
2419 static void function_print(struct type *type, struct value *val)
2421 print_exec(val->function, 1, 0);
2424 static void function_print_type_decl(struct type *type, FILE *f)
2428 for (b = type->function.params; b; b = cast(binode, b->right)) {
2429 struct variable *v = cast(var, b->left)->var;
2430 fprintf(f, "%.*s%s", v->name->name.len, v->name->name.txt,
2431 v->constant ? "::" : ":");
2432 type_print(v->type, f);
2439 static void function_free_type(struct type *t)
2441 free_exec(t->function.params);
2444 static struct type function_prototype = {
2445 .size = sizeof(void*),
2446 .align = sizeof(void*),
2447 .free = function_free,
2448 .compat = function_compat,
2449 .check_args = function_check_args,
2450 .print = function_print,
2451 .print_type_decl = function_print_type_decl,
2452 .free_type = function_free_type,
2455 ###### declare terminals
2465 FuncName -> IDENTIFIER ${ {
2466 struct variable *v = var_decl(c, $1.txt);
2467 struct var *e = new_pos(var, $1);
2473 v = var_ref(c, $1.txt);
2475 type_err(c, "error: function '%v' redeclared",
2477 type_err(c, "info: this is where '%v' was first declared",
2478 v->where_decl, NULL, 0, NULL);
2484 Args -> ArgsLine NEWLINE ${ $0 = $<AL; }$
2485 | Args ArgsLine NEWLINE ${ {
2486 struct binode *b = $<AL;
2487 struct binode **bp = &b;
2489 bp = (struct binode **)&(*bp)->left;
2494 ArgsLine -> ${ $0 = NULL; }$
2495 | Varlist ${ $0 = $<1; }$
2496 | Varlist ; ${ $0 = $<1; }$
2498 Varlist -> Varlist ; ArgDecl ${
2512 ArgDecl -> IDENTIFIER : FormalType ${ {
2513 struct variable *v = var_decl(c, $1.txt);
2519 ## Executables: the elements of code
2521 Each code element needs to be parsed, printed, analysed,
2522 interpreted, and freed. There are several, so let's just start with
2523 the easy ones and work our way up.
2527 We have already met values as separate objects. When manifest
2528 constants appear in the program text, that must result in an executable
2529 which has a constant value. So the `val` structure embeds a value in
2542 ###### ast functions
2543 struct val *new_val(struct type *T, struct token tk)
2545 struct val *v = new_pos(val, tk);
2556 $0 = new_val(Tbool, $1);
2560 $0 = new_val(Tbool, $1);
2564 $0 = new_val(Tnum, $1);
2567 if (number_parse($0->val.num, tail, $1.txt) == 0)
2568 mpq_init($0->val.num); // UNTESTED
2570 tok_err(c, "error: unsupported number suffix",
2575 $0 = new_val(Tstr, $1);
2578 string_parse(&$1, '\\', &$0->val.str, tail);
2580 tok_err(c, "error: unsupported string suffix",
2585 $0 = new_val(Tstr, $1);
2588 string_parse(&$1, '\\', &$0->val.str, tail);
2590 tok_err(c, "error: unsupported string suffix",
2595 ###### print exec cases
2598 struct val *v = cast(val, e);
2599 if (v->vtype == Tstr)
2601 print_value(v->vtype, &v->val);
2602 if (v->vtype == Tstr)
2607 ###### propagate exec cases
2610 struct val *val = cast(val, prog);
2611 if (!type_compat(type, val->vtype, rules))
2612 type_err(c, "error: expected %1%r found %2",
2613 prog, type, rules, val->vtype);
2617 ###### interp exec cases
2619 rvtype = cast(val, e)->vtype;
2620 dup_value(rvtype, &cast(val, e)->val, &rv);
2623 ###### ast functions
2624 static void free_val(struct val *v)
2627 free_value(v->vtype, &v->val);
2631 ###### free exec cases
2632 case Xval: free_val(cast(val, e)); break;
2634 ###### ast functions
2635 // Move all nodes from 'b' to 'rv', reversing their order.
2636 // In 'b' 'left' is a list, and 'right' is the last node.
2637 // In 'rv', left' is the first node and 'right' is a list.
2638 static struct binode *reorder_bilist(struct binode *b)
2640 struct binode *rv = NULL;
2643 struct exec *t = b->right;
2647 b = cast(binode, b->left);
2657 Just as we used a `val` to wrap a value into an `exec`, we similarly
2658 need a `var` to wrap a `variable` into an exec. While each `val`
2659 contained a copy of the value, each `var` holds a link to the variable
2660 because it really is the same variable no matter where it appears.
2661 When a variable is used, we need to remember to follow the `->merged`
2662 link to find the primary instance.
2670 struct variable *var;
2678 VariableDecl -> IDENTIFIER : ${ {
2679 struct variable *v = var_decl(c, $1.txt);
2680 $0 = new_pos(var, $1);
2685 v = var_ref(c, $1.txt);
2687 type_err(c, "error: variable '%v' redeclared",
2689 type_err(c, "info: this is where '%v' was first declared",
2690 v->where_decl, NULL, 0, NULL);
2693 | IDENTIFIER :: ${ {
2694 struct variable *v = var_decl(c, $1.txt);
2695 $0 = new_pos(var, $1);
2701 v = var_ref(c, $1.txt);
2703 type_err(c, "error: variable '%v' redeclared",
2705 type_err(c, "info: this is where '%v' was first declared",
2706 v->where_decl, NULL, 0, NULL);
2709 | IDENTIFIER : Type ${ {
2710 struct variable *v = var_decl(c, $1.txt);
2711 $0 = new_pos(var, $1);
2718 v = var_ref(c, $1.txt);
2720 type_err(c, "error: variable '%v' redeclared",
2722 type_err(c, "info: this is where '%v' was first declared",
2723 v->where_decl, NULL, 0, NULL);
2726 | IDENTIFIER :: Type ${ {
2727 struct variable *v = var_decl(c, $1.txt);
2728 $0 = new_pos(var, $1);
2736 v = var_ref(c, $1.txt);
2738 type_err(c, "error: variable '%v' redeclared",
2740 type_err(c, "info: this is where '%v' was first declared",
2741 v->where_decl, NULL, 0, NULL);
2746 Variable -> IDENTIFIER ${ {
2747 struct variable *v = var_ref(c, $1.txt);
2748 $0 = new_pos(var, $1);
2750 /* This might be a label - allocate a var just in case */
2751 v = var_decl(c, $1.txt);
2758 cast(var, $0)->var = v;
2762 ###### print exec cases
2765 struct var *v = cast(var, e);
2767 struct binding *b = v->var->name;
2768 printf("%.*s", b->name.len, b->name.txt);
2775 if (loc && loc->type == Xvar) {
2776 struct var *v = cast(var, loc);
2778 struct binding *b = v->var->name;
2779 fprintf(stderr, "%.*s", b->name.len, b->name.txt);
2781 fputs("???", stderr); // NOTEST
2783 fputs("NOTVAR", stderr);
2786 ###### propagate exec cases
2790 struct var *var = cast(var, prog);
2791 struct variable *v = var->var;
2793 type_err(c, "%d:BUG: no variable!!", prog, NULL, 0, NULL); // NOTEST
2794 return Tnone; // NOTEST
2797 if (v->constant && (rules & Rnoconstant)) {
2798 type_err(c, "error: Cannot assign to a constant: %v",
2799 prog, NULL, 0, NULL);
2800 type_err(c, "info: name was defined as a constant here",
2801 v->where_decl, NULL, 0, NULL);
2804 if (v->type == Tnone && v->where_decl == prog)
2805 type_err(c, "error: variable used but not declared: %v",
2806 prog, NULL, 0, NULL);
2807 if (v->type == NULL) {
2808 if (type && *ok != 0) {
2810 v->where_set = prog;
2815 if (!type_compat(type, v->type, rules)) {
2816 type_err(c, "error: expected %1%r but variable '%v' is %2", prog,
2817 type, rules, v->type);
2818 type_err(c, "info: this is where '%v' was set to %1", v->where_set,
2819 v->type, rules, NULL);
2826 ###### interp exec cases
2829 struct var *var = cast(var, e);
2830 struct variable *v = var->var;
2833 lrv = var_value(c, v);
2838 ###### ast functions
2840 static void free_var(struct var *v)
2845 ###### free exec cases
2846 case Xvar: free_var(cast(var, e)); break;
2848 ### Expressions: Conditional
2850 Our first user of the `binode` will be conditional expressions, which
2851 is a bit odd as they actually have three components. That will be
2852 handled by having 2 binodes for each expression. The conditional
2853 expression is the lowest precedence operator which is why we define it
2854 first - to start the precedence list.
2856 Conditional expressions are of the form "value `if` condition `else`
2857 other_value". They associate to the right, so everything to the right
2858 of `else` is part of an else value, while only a higher-precedence to
2859 the left of `if` is the if values. Between `if` and `else` there is no
2860 room for ambiguity, so a full conditional expression is allowed in
2872 Expression -> Expression if Expression else Expression $$ifelse ${ {
2873 struct binode *b1 = new(binode);
2874 struct binode *b2 = new(binode);
2883 ## expression grammar
2885 ###### print binode cases
2888 b2 = cast(binode, b->right);
2889 if (bracket) printf("(");
2890 print_exec(b2->left, -1, bracket);
2892 print_exec(b->left, -1, bracket);
2894 print_exec(b2->right, -1, bracket);
2895 if (bracket) printf(")");
2898 ###### propagate binode cases
2901 /* cond must be Tbool, others must match */
2902 struct binode *b2 = cast(binode, b->right);
2905 propagate_types(b->left, c, ok, Tbool, 0);
2906 t = propagate_types(b2->left, c, ok, type, Rnolabel);
2907 t2 = propagate_types(b2->right, c, ok, type ?: t, Rnolabel);
2911 ###### interp binode cases
2914 struct binode *b2 = cast(binode, b->right);
2915 left = interp_exec(c, b->left, <ype);
2917 rv = interp_exec(c, b2->left, &rvtype); // UNTESTED
2919 rv = interp_exec(c, b2->right, &rvtype);
2925 We take a brief detour, now that we have expressions, to describe lists
2926 of expressions. These will be needed for function parameters and
2927 possibly other situations. They seem generic enough to introduce here
2928 to be used elsewhere.
2930 And ExpressionList will use the `List` type of `binode`, building up at
2931 the end. And place where they are used will probably call
2932 `reorder_bilist()` to get a more normal first/next arrangement.
2934 ###### declare terminals
2937 `List` execs have no implicit semantics, so they are never propagated or
2938 interpreted. The can be printed as a comma separate list, which is how
2939 they are parsed. Note they are also used for function formal parameter
2940 lists. In that case a separate function is used to print them.
2942 ###### print binode cases
2946 print_exec(b->left, -1, bracket);
2949 b = cast(binode, b->right);
2953 ###### propagate binode cases
2954 case List: abort(); // NOTEST
2955 ###### interp binode cases
2956 case List: abort(); // NOTEST
2961 ExpressionList -> ExpressionList , Expression ${
2974 ### Expressions: Boolean
2976 The next class of expressions to use the `binode` will be Boolean
2977 expressions. "`and then`" and "`or else`" are similar to `and` and `or`
2978 have same corresponding precendence. The difference is that they don't
2979 evaluate the second expression if not necessary.
2988 ###### expr precedence
2993 ###### expression grammar
2994 | Expression or Expression ${ {
2995 struct binode *b = new(binode);
3001 | Expression or else Expression ${ {
3002 struct binode *b = new(binode);
3009 | Expression and Expression ${ {
3010 struct binode *b = new(binode);
3016 | Expression and then Expression ${ {
3017 struct binode *b = new(binode);
3024 | not Expression ${ {
3025 struct binode *b = new(binode);
3031 ###### print binode cases
3033 if (bracket) printf("(");
3034 print_exec(b->left, -1, bracket);
3036 print_exec(b->right, -1, bracket);
3037 if (bracket) printf(")");
3040 if (bracket) printf("(");
3041 print_exec(b->left, -1, bracket);
3042 printf(" and then ");
3043 print_exec(b->right, -1, bracket);
3044 if (bracket) printf(")");
3047 if (bracket) printf("(");
3048 print_exec(b->left, -1, bracket);
3050 print_exec(b->right, -1, bracket);
3051 if (bracket) printf(")");
3054 if (bracket) printf("(");
3055 print_exec(b->left, -1, bracket);
3056 printf(" or else ");
3057 print_exec(b->right, -1, bracket);
3058 if (bracket) printf(")");
3061 if (bracket) printf("(");
3063 print_exec(b->right, -1, bracket);
3064 if (bracket) printf(")");
3067 ###### propagate binode cases
3073 /* both must be Tbool, result is Tbool */
3074 propagate_types(b->left, c, ok, Tbool, 0);
3075 propagate_types(b->right, c, ok, Tbool, 0);
3076 if (type && type != Tbool)
3077 type_err(c, "error: %1 operation found where %2 expected", prog,
3081 ###### interp binode cases
3083 rv = interp_exec(c, b->left, &rvtype);
3084 right = interp_exec(c, b->right, &rtype);
3085 rv.bool = rv.bool && right.bool;
3088 rv = interp_exec(c, b->left, &rvtype);
3090 rv = interp_exec(c, b->right, NULL);
3093 rv = interp_exec(c, b->left, &rvtype);
3094 right = interp_exec(c, b->right, &rtype);
3095 rv.bool = rv.bool || right.bool;
3098 rv = interp_exec(c, b->left, &rvtype);
3100 rv = interp_exec(c, b->right, NULL);
3103 rv = interp_exec(c, b->right, &rvtype);
3107 ### Expressions: Comparison
3109 Of slightly higher precedence that Boolean expressions are Comparisons.
3110 A comparison takes arguments of any comparable type, but the two types
3113 To simplify the parsing we introduce an `eop` which can record an
3114 expression operator, and the `CMPop` non-terminal will match one of them.
3121 ###### ast functions
3122 static void free_eop(struct eop *e)
3136 ###### expr precedence
3137 $LEFT < > <= >= == != CMPop
3139 ###### expression grammar
3140 | Expression CMPop Expression ${ {
3141 struct binode *b = new(binode);
3151 CMPop -> < ${ $0.op = Less; }$
3152 | > ${ $0.op = Gtr; }$
3153 | <= ${ $0.op = LessEq; }$
3154 | >= ${ $0.op = GtrEq; }$
3155 | == ${ $0.op = Eql; }$
3156 | != ${ $0.op = NEql; }$
3158 ###### print binode cases
3166 if (bracket) printf("(");
3167 print_exec(b->left, -1, bracket);
3169 case Less: printf(" < "); break;
3170 case LessEq: printf(" <= "); break;
3171 case Gtr: printf(" > "); break;
3172 case GtrEq: printf(" >= "); break;
3173 case Eql: printf(" == "); break;
3174 case NEql: printf(" != "); break;
3175 default: abort(); // NOTEST
3177 print_exec(b->right, -1, bracket);
3178 if (bracket) printf(")");
3181 ###### propagate binode cases
3188 /* Both must match but not be labels, result is Tbool */
3189 t = propagate_types(b->left, c, ok, NULL, Rnolabel);
3191 propagate_types(b->right, c, ok, t, 0);
3193 t = propagate_types(b->right, c, ok, NULL, Rnolabel); // UNTESTED
3195 t = propagate_types(b->left, c, ok, t, 0); // UNTESTED
3197 if (!type_compat(type, Tbool, 0))
3198 type_err(c, "error: Comparison returns %1 but %2 expected", prog,
3199 Tbool, rules, type);
3202 ###### interp binode cases
3211 left = interp_exec(c, b->left, <ype);
3212 right = interp_exec(c, b->right, &rtype);
3213 cmp = value_cmp(ltype, rtype, &left, &right);
3216 case Less: rv.bool = cmp < 0; break;
3217 case LessEq: rv.bool = cmp <= 0; break;
3218 case Gtr: rv.bool = cmp > 0; break;
3219 case GtrEq: rv.bool = cmp >= 0; break;
3220 case Eql: rv.bool = cmp == 0; break;
3221 case NEql: rv.bool = cmp != 0; break;
3222 default: rv.bool = 0; break; // NOTEST
3227 ### Expressions: Arithmetic etc.
3229 The remaining expressions with the highest precedence are arithmetic,
3230 string concatenation, and string conversion. String concatenation
3231 (`++`) has the same precedence as multiplication and division, but lower
3234 String conversion is a temporary feature until I get a better type
3235 system. `$` is a prefix operator which expects a string and returns
3238 `+` and `-` are both infix and prefix operations (where they are
3239 absolute value and negation). These have different operator names.
3241 We also have a 'Bracket' operator which records where parentheses were
3242 found. This makes it easy to reproduce these when printing. Possibly I
3243 should only insert brackets were needed for precedence.
3253 ###### expr precedence
3259 ###### expression grammar
3260 | Expression Eop Expression ${ {
3261 struct binode *b = new(binode);
3268 | Expression Top Expression ${ {
3269 struct binode *b = new(binode);
3276 | ( Expression ) ${ {
3277 struct binode *b = new_pos(binode, $1);
3282 | Uop Expression ${ {
3283 struct binode *b = new(binode);
3288 | Value ${ $0 = $<1; }$
3289 | Variable ${ $0 = $<1; }$
3294 Eop -> + ${ $0.op = Plus; }$
3295 | - ${ $0.op = Minus; }$
3297 Uop -> + ${ $0.op = Absolute; }$
3298 | - ${ $0.op = Negate; }$
3299 | $ ${ $0.op = StringConv; }$
3301 Top -> * ${ $0.op = Times; }$
3302 | / ${ $0.op = Divide; }$
3303 | % ${ $0.op = Rem; }$
3304 | ++ ${ $0.op = Concat; }$
3306 ###### print binode cases
3313 if (bracket) printf("(");
3314 print_exec(b->left, indent, bracket);
3316 case Plus: fputs(" + ", stdout); break;
3317 case Minus: fputs(" - ", stdout); break;
3318 case Times: fputs(" * ", stdout); break;
3319 case Divide: fputs(" / ", stdout); break;
3320 case Rem: fputs(" % ", stdout); break;
3321 case Concat: fputs(" ++ ", stdout); break;
3322 default: abort(); // NOTEST
3324 print_exec(b->right, indent, bracket);
3325 if (bracket) printf(")");
3330 if (bracket) printf("(");
3332 case Absolute: fputs("+", stdout); break;
3333 case Negate: fputs("-", stdout); break;
3334 case StringConv: fputs("$", stdout); break;
3335 default: abort(); // NOTEST
3337 print_exec(b->right, indent, bracket);
3338 if (bracket) printf(")");
3342 print_exec(b->right, indent, bracket);
3346 ###### propagate binode cases
3352 /* both must be numbers, result is Tnum */
3355 /* as propagate_types ignores a NULL,
3356 * unary ops fit here too */
3357 propagate_types(b->left, c, ok, Tnum, 0);
3358 propagate_types(b->right, c, ok, Tnum, 0);
3359 if (!type_compat(type, Tnum, 0))
3360 type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
3365 /* both must be Tstr, result is Tstr */
3366 propagate_types(b->left, c, ok, Tstr, 0);
3367 propagate_types(b->right, c, ok, Tstr, 0);
3368 if (!type_compat(type, Tstr, 0))
3369 type_err(c, "error: Concat returns %1 but %2 expected", prog,
3374 /* op must be string, result is number */
3375 propagate_types(b->left, c, ok, Tstr, 0);
3376 if (!type_compat(type, Tnum, 0))
3377 type_err(c, // UNTESTED
3378 "error: Can only convert string to number, not %1",
3379 prog, type, 0, NULL);
3383 return propagate_types(b->right, c, ok, type, 0);
3385 ###### interp binode cases
3388 rv = interp_exec(c, b->left, &rvtype);
3389 right = interp_exec(c, b->right, &rtype);
3390 mpq_add(rv.num, rv.num, right.num);
3393 rv = interp_exec(c, b->left, &rvtype);
3394 right = interp_exec(c, b->right, &rtype);
3395 mpq_sub(rv.num, rv.num, right.num);
3398 rv = interp_exec(c, b->left, &rvtype);
3399 right = interp_exec(c, b->right, &rtype);
3400 mpq_mul(rv.num, rv.num, right.num);
3403 rv = interp_exec(c, b->left, &rvtype);
3404 right = interp_exec(c, b->right, &rtype);
3405 mpq_div(rv.num, rv.num, right.num);
3410 left = interp_exec(c, b->left, <ype);
3411 right = interp_exec(c, b->right, &rtype);
3412 mpz_init(l); mpz_init(r); mpz_init(rem);
3413 mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
3414 mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
3415 mpz_tdiv_r(rem, l, r);
3416 val_init(Tnum, &rv);
3417 mpq_set_z(rv.num, rem);
3418 mpz_clear(r); mpz_clear(l); mpz_clear(rem);
3423 rv = interp_exec(c, b->right, &rvtype);
3424 mpq_neg(rv.num, rv.num);
3427 rv = interp_exec(c, b->right, &rvtype);
3428 mpq_abs(rv.num, rv.num);
3431 rv = interp_exec(c, b->right, &rvtype);
3434 left = interp_exec(c, b->left, <ype);
3435 right = interp_exec(c, b->right, &rtype);
3437 rv.str = text_join(left.str, right.str);
3440 right = interp_exec(c, b->right, &rvtype);
3444 struct text tx = right.str;
3447 if (tx.txt[0] == '-') {
3448 neg = 1; // UNTESTED
3449 tx.txt++; // UNTESTED
3450 tx.len--; // UNTESTED
3452 if (number_parse(rv.num, tail, tx) == 0)
3453 mpq_init(rv.num); // UNTESTED
3455 mpq_neg(rv.num, rv.num); // UNTESTED
3457 printf("Unsupported suffix: %.*s\n", tx.len, tx.txt); // UNTESTED
3461 ###### value functions
3463 static struct text text_join(struct text a, struct text b)
3466 rv.len = a.len + b.len;
3467 rv.txt = malloc(rv.len);
3468 memcpy(rv.txt, a.txt, a.len);
3469 memcpy(rv.txt+a.len, b.txt, b.len);
3475 A function call can appear either as an expression or as a statement.
3476 As functions cannot yet return values, only the statement version will work.
3477 We use a new 'Funcall' binode type to link the function with a list of
3478 arguments, form with the 'List' nodes.
3483 ###### expression grammar
3484 | Variable ( ExpressionList ) ${ {
3485 struct binode *b = new(binode);
3488 b->right = reorder_bilist($<EL);
3492 struct binode *b = new(binode);
3499 ###### SimpleStatement Grammar
3501 | Variable ( ExpressionList ) ${ {
3502 struct binode *b = new(binode);
3505 b->right = reorder_bilist($<EL);
3509 ###### print binode cases
3512 do_indent(indent, "");
3513 print_exec(b->left, -1, bracket);
3515 for (b = cast(binode, b->right); b; b = cast(binode, b->right)) {
3518 print_exec(b->left, -1, bracket);
3528 ###### propagate binode cases
3531 /* Every arg must match formal parameter, and result
3532 * is return type of function (currently Tnone).
3534 struct binode *args = cast(binode, b->right);
3535 struct var *v = cast(var, b->left);
3537 if (!v->var->type || v->var->type->check_args == NULL) {
3538 type_err(c, "error: attempt to call a non-function.",
3539 prog, NULL, 0, NULL);
3542 v->var->type->check_args(c, ok, v->var->type, args);
3546 ###### interp binode cases
3549 struct var *v = cast(var, b->left);
3550 struct type *t = v->var->type;
3551 void *oldlocal = c->local;
3552 int old_size = c->local_size;
3553 void *local = calloc(1, t->function.local_size);
3554 struct value *fbody = var_value(c, v->var);
3555 struct binode *arg = cast(binode, b->right);
3556 struct binode *param = t->function.params;
3559 struct var *pv = cast(var, param->left);
3560 struct type *vtype = NULL;
3561 struct value val = interp_exec(c, arg->left, &vtype);
3563 c->local = local; c->local_size = t->function.local_size;
3564 lval = var_value(c, pv->var);
3565 c->local = oldlocal; c->local_size = old_size;
3566 memcpy(lval, &val, vtype->size);
3567 param = cast(binode, param->right);
3568 arg = cast(binode, arg->right);
3570 c->local = local; c->local_size = t->function.local_size;
3571 right = interp_exec(c, fbody->function, &rtype);
3572 c->local = oldlocal; c->local_size = old_size;
3577 ### Blocks, Statements, and Statement lists.
3579 Now that we have expressions out of the way we need to turn to
3580 statements. There are simple statements and more complex statements.
3581 Simple statements do not contain (syntactic) newlines, complex statements do.
3583 Statements often come in sequences and we have corresponding simple
3584 statement lists and complex statement lists.
3585 The former comprise only simple statements separated by semicolons.
3586 The later comprise complex statements and simple statement lists. They are
3587 separated by newlines. Thus the semicolon is only used to separate
3588 simple statements on the one line. This may be overly restrictive,
3589 but I'm not sure I ever want a complex statement to share a line with
3592 Note that a simple statement list can still use multiple lines if
3593 subsequent lines are indented, so
3595 ###### Example: wrapped simple statement list
3600 is a single simple statement list. This might allow room for
3601 confusion, so I'm not set on it yet.
3603 A simple statement list needs no extra syntax. A complex statement
3604 list has two syntactic forms. It can be enclosed in braces (much like
3605 C blocks), or it can be introduced by an indent and continue until an
3606 unindented newline (much like Python blocks). With this extra syntax
3607 it is referred to as a block.
3609 Note that a block does not have to include any newlines if it only
3610 contains simple statements. So both of:
3612 if condition: a=b; d=f
3614 if condition { a=b; print f }
3618 In either case the list is constructed from a `binode` list with
3619 `Block` as the operator. When parsing the list it is most convenient
3620 to append to the end, so a list is a list and a statement. When using
3621 the list it is more convenient to consider a list to be a statement
3622 and a list. So we need a function to re-order a list.
3623 `reorder_bilist` serves this purpose.
3625 The only stand-alone statement we introduce at this stage is `pass`
3626 which does nothing and is represented as a `NULL` pointer in a `Block`
3627 list. Other stand-alone statements will follow once the infrastructure
3638 Block -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3639 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3640 | SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3641 | SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3642 | IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3644 OpenBlock -> OpenScope { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3645 | OpenScope { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3646 | OpenScope SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3647 | OpenScope SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3648 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3650 UseBlock -> { OpenScope IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3651 | { OpenScope SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3652 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3654 ColonBlock -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3655 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3656 | : SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3657 | : SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3658 | : IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3660 Statementlist -> ComplexStatements ${ $0 = reorder_bilist($<CS); }$
3662 ComplexStatements -> ComplexStatements ComplexStatement ${
3672 | ComplexStatement ${
3684 ComplexStatement -> SimpleStatements Newlines ${
3685 $0 = reorder_bilist($<SS);
3687 | SimpleStatements ; Newlines ${
3688 $0 = reorder_bilist($<SS);
3690 ## ComplexStatement Grammar
3693 SimpleStatements -> SimpleStatements ; SimpleStatement ${
3699 | SimpleStatement ${
3707 SimpleStatement -> pass ${ $0 = NULL; }$
3708 | ERROR ${ tok_err(c, "Syntax error in statement", &$1); }$
3709 ## SimpleStatement Grammar
3711 ###### print binode cases
3715 if (b->left == NULL) // UNTESTED
3716 printf("pass"); // UNTESTED
3718 print_exec(b->left, indent, bracket); // UNTESTED
3719 if (b->right) { // UNTESTED
3720 printf("; "); // UNTESTED
3721 print_exec(b->right, indent, bracket); // UNTESTED
3724 // block, one per line
3725 if (b->left == NULL)
3726 do_indent(indent, "pass\n");
3728 print_exec(b->left, indent, bracket);
3730 print_exec(b->right, indent, bracket);
3734 ###### propagate binode cases
3737 /* If any statement returns something other than Tnone
3738 * or Tbool then all such must return same type.
3739 * As each statement may be Tnone or something else,
3740 * we must always pass NULL (unknown) down, otherwise an incorrect
3741 * error might occur. We never return Tnone unless it is
3746 for (e = b; e; e = cast(binode, e->right)) {
3747 t = propagate_types(e->left, c, ok, NULL, rules);
3748 if ((rules & Rboolok) && (t == Tbool || t == Tnone))
3750 if (t == Tnone && e->right)
3751 /* Only the final statement *must* return a value
3759 type_err(c, "error: expected %1%r, found %2",
3760 e->left, type, rules, t);
3766 ###### interp binode cases
3768 while (rvtype == Tnone &&
3771 rv = interp_exec(c, b->left, &rvtype);
3772 b = cast(binode, b->right);
3776 ### The Print statement
3778 `print` is a simple statement that takes a comma-separated list of
3779 expressions and prints the values separated by spaces and terminated
3780 by a newline. No control of formatting is possible.
3782 `print` uses `ExpressionList` to collect the expressions and stores them
3783 on the left side of a `Print` binode unlessthere is a trailing comma
3784 when the list is stored on the `right` side and no trailing newline is
3790 ##### expr precedence
3793 ###### SimpleStatement Grammar
3795 | print ExpressionList ${
3799 $0->left = reorder_bilist($<EL);
3801 | print ExpressionList , ${ {
3804 $0->right = reorder_bilist($<EL);
3814 ###### print binode cases
3817 do_indent(indent, "print");
3819 print_exec(b->right, -1, bracket);
3822 print_exec(b->left, -1, bracket);
3827 ###### propagate binode cases
3830 /* don't care but all must be consistent */
3832 b = cast(binode, b->left);
3834 b = cast(binode, b->right);
3836 propagate_types(b->left, c, ok, NULL, Rnolabel);
3837 b = cast(binode, b->right);
3841 ###### interp binode cases
3845 struct binode *b2 = cast(binode, b->left);
3847 b2 = cast(binode, b->right);
3848 for (; b2; b2 = cast(binode, b2->right)) {
3849 left = interp_exec(c, b2->left, <ype);
3850 print_value(ltype, &left);
3851 free_value(ltype, &left);
3855 if (b->right == NULL)
3861 ###### Assignment statement
3863 An assignment will assign a value to a variable, providing it hasn't
3864 been declared as a constant. The analysis phase ensures that the type
3865 will be correct so the interpreter just needs to perform the
3866 calculation. There is a form of assignment which declares a new
3867 variable as well as assigning a value. If a name is assigned before
3868 it is declared, and error will be raised as the name is created as
3869 `Tlabel` and it is illegal to assign to such names.
3875 ###### declare terminals
3878 ###### SimpleStatement Grammar
3879 | Variable = Expression ${
3885 | VariableDecl = Expression ${
3893 if ($1->var->where_set == NULL) {
3895 "Variable declared with no type or value: %v",
3905 ###### print binode cases
3908 do_indent(indent, "");
3909 print_exec(b->left, indent, bracket);
3911 print_exec(b->right, indent, bracket);
3918 struct variable *v = cast(var, b->left)->var;
3919 do_indent(indent, "");
3920 print_exec(b->left, indent, bracket);
3921 if (cast(var, b->left)->var->constant) {
3923 if (v->where_decl == v->where_set) {
3924 type_print(v->type, stdout);
3929 if (v->where_decl == v->where_set) {
3930 type_print(v->type, stdout);
3936 print_exec(b->right, indent, bracket);
3943 ###### propagate binode cases
3947 /* Both must match and not be labels,
3948 * Type must support 'dup',
3949 * For Assign, left must not be constant.
3952 t = propagate_types(b->left, c, ok, NULL,
3953 Rnolabel | (b->op == Assign ? Rnoconstant : 0));
3958 if (propagate_types(b->right, c, ok, t, 0) != t)
3959 if (b->left->type == Xvar)
3960 type_err(c, "info: variable '%v' was set as %1 here.",
3961 cast(var, b->left)->var->where_set, t, rules, NULL);
3963 t = propagate_types(b->right, c, ok, NULL, Rnolabel);
3965 propagate_types(b->left, c, ok, t,
3966 (b->op == Assign ? Rnoconstant : 0));
3968 if (t && t->dup == NULL)
3969 type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
3974 ###### interp binode cases
3977 lleft = linterp_exec(c, b->left, <ype);
3978 right = interp_exec(c, b->right, &rtype);
3980 free_value(ltype, lleft);
3981 dup_value(ltype, &right, lleft);
3988 struct variable *v = cast(var, b->left)->var;
3991 val = var_value(c, v);
3992 if (v->type->prepare_type)
3993 v->type->prepare_type(c, v->type, 0);
3995 right = interp_exec(c, b->right, &rtype);
3996 memcpy(val, &right, rtype->size);
3999 val_init(v->type, val);
4004 ### The `use` statement
4006 The `use` statement is the last "simple" statement. It is needed when
4007 the condition in a conditional statement is a block. `use` works much
4008 like `return` in C, but only completes the `condition`, not the whole
4014 ###### expr precedence
4017 ###### SimpleStatement Grammar
4019 $0 = new_pos(binode, $1);
4022 if ($0->right->type == Xvar) {
4023 struct var *v = cast(var, $0->right);
4024 if (v->var->type == Tnone) {
4025 /* Convert this to a label */
4028 v->var->type = Tlabel;
4029 val = global_alloc(c, Tlabel, v->var, NULL);
4035 ###### print binode cases
4038 do_indent(indent, "use ");
4039 print_exec(b->right, -1, bracket);
4044 ###### propagate binode cases
4047 /* result matches value */
4048 return propagate_types(b->right, c, ok, type, 0);
4050 ###### interp binode cases
4053 rv = interp_exec(c, b->right, &rvtype);
4056 ### The Conditional Statement
4058 This is the biggy and currently the only complex statement. This
4059 subsumes `if`, `while`, `do/while`, `switch`, and some parts of `for`.
4060 It is comprised of a number of parts, all of which are optional though
4061 set combinations apply. Each part is (usually) a key word (`then` is
4062 sometimes optional) followed by either an expression or a code block,
4063 except the `casepart` which is a "key word and an expression" followed
4064 by a code block. The code-block option is valid for all parts and,
4065 where an expression is also allowed, the code block can use the `use`
4066 statement to report a value. If the code block does not report a value
4067 the effect is similar to reporting `True`.
4069 The `else` and `case` parts, as well as `then` when combined with
4070 `if`, can contain a `use` statement which will apply to some
4071 containing conditional statement. `for` parts, `do` parts and `then`
4072 parts used with `for` can never contain a `use`, except in some
4073 subordinate conditional statement.
4075 If there is a `forpart`, it is executed first, only once.
4076 If there is a `dopart`, then it is executed repeatedly providing
4077 always that the `condpart` or `cond`, if present, does not return a non-True
4078 value. `condpart` can fail to return any value if it simply executes
4079 to completion. This is treated the same as returning `True`.
4081 If there is a `thenpart` it will be executed whenever the `condpart`
4082 or `cond` returns True (or does not return any value), but this will happen
4083 *after* `dopart` (when present).
4085 If `elsepart` is present it will be executed at most once when the
4086 condition returns `False` or some value that isn't `True` and isn't
4087 matched by any `casepart`. If there are any `casepart`s, they will be
4088 executed when the condition returns a matching value.
4090 The particular sorts of values allowed in case parts has not yet been
4091 determined in the language design, so nothing is prohibited.
4093 The various blocks in this complex statement potentially provide scope
4094 for variables as described earlier. Each such block must include the
4095 "OpenScope" nonterminal before parsing the block, and must call
4096 `var_block_close()` when closing the block.
4098 The code following "`if`", "`switch`" and "`for`" does not get its own
4099 scope, but is in a scope covering the whole statement, so names
4100 declared there cannot be redeclared elsewhere. Similarly the
4101 condition following "`while`" is in a scope the covers the body
4102 ("`do`" part) of the loop, and which does not allow conditional scope
4103 extension. Code following "`then`" (both looping and non-looping),
4104 "`else`" and "`case`" each get their own local scope.
4106 The type requirements on the code block in a `whilepart` are quite
4107 unusal. It is allowed to return a value of some identifiable type, in
4108 which case the loop aborts and an appropriate `casepart` is run, or it
4109 can return a Boolean, in which case the loop either continues to the
4110 `dopart` (on `True`) or aborts and runs the `elsepart` (on `False`).
4111 This is different both from the `ifpart` code block which is expected to
4112 return a Boolean, or the `switchpart` code block which is expected to
4113 return the same type as the casepart values. The correct analysis of
4114 the type of the `whilepart` code block is the reason for the
4115 `Rboolok` flag which is passed to `propagate_types()`.
4117 The `cond_statement` cannot fit into a `binode` so a new `exec` is
4118 defined. As there are two scopes which cover multiple parts - one for
4119 the whole statement and one for "while" and "do" - and as we will use
4120 the 'struct exec' to track scopes, we actually need two new types of
4121 exec. One is a `binode` for the looping part, the rest is the
4122 `cond_statement`. The `cond_statement` will use an auxilliary `struct
4123 casepart` to track a list of case parts.
4134 struct exec *action;
4135 struct casepart *next;
4137 struct cond_statement {
4139 struct exec *forpart, *condpart, *thenpart, *elsepart;
4140 struct binode *looppart;
4141 struct casepart *casepart;
4144 ###### ast functions
4146 static void free_casepart(struct casepart *cp)
4150 free_exec(cp->value);
4151 free_exec(cp->action);
4158 static void free_cond_statement(struct cond_statement *s)
4162 free_exec(s->forpart);
4163 free_exec(s->condpart);
4164 free_exec(s->looppart);
4165 free_exec(s->thenpart);
4166 free_exec(s->elsepart);
4167 free_casepart(s->casepart);
4171 ###### free exec cases
4172 case Xcond_statement: free_cond_statement(cast(cond_statement, e)); break;
4174 ###### ComplexStatement Grammar
4175 | CondStatement ${ $0 = $<1; }$
4177 ###### expr precedence
4178 $TERM for then while do
4185 // A CondStatement must end with EOL, as does CondSuffix and
4187 // ForPart, ThenPart, SwitchPart, CasePart are non-empty and
4188 // may or may not end with EOL
4189 // WhilePart and IfPart include an appropriate Suffix
4191 // ForPart, SwitchPart, and IfPart open scopes, o we have to close
4192 // them. WhilePart opens and closes its own scope.
4193 CondStatement -> ForPart OptNL ThenPart OptNL WhilePart CondSuffix ${
4196 $0->thenpart = $<TP;
4197 $0->looppart = $<WP;
4198 var_block_close(c, CloseSequential, $0);
4200 | ForPart OptNL WhilePart CondSuffix ${
4203 $0->looppart = $<WP;
4204 var_block_close(c, CloseSequential, $0);
4206 | WhilePart CondSuffix ${
4208 $0->looppart = $<WP;
4210 | SwitchPart OptNL CasePart CondSuffix ${
4212 $0->condpart = $<SP;
4213 $CP->next = $0->casepart;
4214 $0->casepart = $<CP;
4215 var_block_close(c, CloseSequential, $0);
4217 | SwitchPart : IN OptNL CasePart CondSuffix OUT Newlines ${
4219 $0->condpart = $<SP;
4220 $CP->next = $0->casepart;
4221 $0->casepart = $<CP;
4222 var_block_close(c, CloseSequential, $0);
4224 | IfPart IfSuffix ${
4226 $0->condpart = $IP.condpart; $IP.condpart = NULL;
4227 $0->thenpart = $IP.thenpart; $IP.thenpart = NULL;
4228 // This is where we close an "if" statement
4229 var_block_close(c, CloseSequential, $0);
4232 CondSuffix -> IfSuffix ${
4235 | Newlines CasePart CondSuffix ${
4237 $CP->next = $0->casepart;
4238 $0->casepart = $<CP;
4240 | CasePart CondSuffix ${
4242 $CP->next = $0->casepart;
4243 $0->casepart = $<CP;
4246 IfSuffix -> Newlines ${ $0 = new(cond_statement); }$
4247 | Newlines ElsePart ${ $0 = $<EP; }$
4248 | ElsePart ${$0 = $<EP; }$
4250 ElsePart -> else OpenBlock Newlines ${
4251 $0 = new(cond_statement);
4252 $0->elsepart = $<OB;
4253 var_block_close(c, CloseElse, $0->elsepart);
4255 | else OpenScope CondStatement ${
4256 $0 = new(cond_statement);
4257 $0->elsepart = $<CS;
4258 var_block_close(c, CloseElse, $0->elsepart);
4262 CasePart -> case Expression OpenScope ColonBlock ${
4263 $0 = calloc(1,sizeof(struct casepart));
4266 var_block_close(c, CloseParallel, $0->action);
4270 // These scopes are closed in CondStatement
4271 ForPart -> for OpenBlock ${
4275 ThenPart -> then OpenBlock ${
4277 var_block_close(c, CloseSequential, $0);
4281 // This scope is closed in CondStatement
4282 WhilePart -> while UseBlock OptNL do OpenBlock ${
4287 var_block_close(c, CloseSequential, $0->right);
4288 var_block_close(c, CloseSequential, $0);
4290 | while OpenScope Expression OpenScope ColonBlock ${
4295 var_block_close(c, CloseSequential, $0->right);
4296 var_block_close(c, CloseSequential, $0);
4300 IfPart -> if UseBlock OptNL then OpenBlock ${
4303 var_block_close(c, CloseParallel, $0.thenpart);
4305 | if OpenScope Expression OpenScope ColonBlock ${
4308 var_block_close(c, CloseParallel, $0.thenpart);
4310 | if OpenScope Expression OpenScope OptNL then Block ${
4313 var_block_close(c, CloseParallel, $0.thenpart);
4317 // This scope is closed in CondStatement
4318 SwitchPart -> switch OpenScope Expression ${
4321 | switch UseBlock ${
4325 ###### print binode cases
4327 if (b->left && b->left->type == Xbinode &&
4328 cast(binode, b->left)->op == Block) {
4330 do_indent(indent, "while {\n");
4332 do_indent(indent, "while\n");
4333 print_exec(b->left, indent+1, bracket);
4335 do_indent(indent, "} do {\n");
4337 do_indent(indent, "do\n");
4338 print_exec(b->right, indent+1, bracket);
4340 do_indent(indent, "}\n");
4342 do_indent(indent, "while ");
4343 print_exec(b->left, 0, bracket);
4348 print_exec(b->right, indent+1, bracket);
4350 do_indent(indent, "}\n");
4354 ###### print exec cases
4356 case Xcond_statement:
4358 struct cond_statement *cs = cast(cond_statement, e);
4359 struct casepart *cp;
4361 do_indent(indent, "for");
4362 if (bracket) printf(" {\n"); else printf("\n");
4363 print_exec(cs->forpart, indent+1, bracket);
4366 do_indent(indent, "} then {\n");
4368 do_indent(indent, "then\n");
4369 print_exec(cs->thenpart, indent+1, bracket);
4371 if (bracket) do_indent(indent, "}\n");
4374 print_exec(cs->looppart, indent, bracket);
4378 do_indent(indent, "switch");
4380 do_indent(indent, "if");
4381 if (cs->condpart && cs->condpart->type == Xbinode &&
4382 cast(binode, cs->condpart)->op == Block) {
4387 print_exec(cs->condpart, indent+1, bracket);
4389 do_indent(indent, "}\n");
4391 do_indent(indent, "then\n");
4392 print_exec(cs->thenpart, indent+1, bracket);
4396 print_exec(cs->condpart, 0, bracket);
4402 print_exec(cs->thenpart, indent+1, bracket);
4404 do_indent(indent, "}\n");
4409 for (cp = cs->casepart; cp; cp = cp->next) {
4410 do_indent(indent, "case ");
4411 print_exec(cp->value, -1, 0);
4416 print_exec(cp->action, indent+1, bracket);
4418 do_indent(indent, "}\n");
4421 do_indent(indent, "else");
4426 print_exec(cs->elsepart, indent+1, bracket);
4428 do_indent(indent, "}\n");
4433 ###### propagate binode cases
4435 t = propagate_types(b->right, c, ok, Tnone, 0);
4436 if (!type_compat(Tnone, t, 0))
4437 *ok = 0; // UNTESTED
4438 return propagate_types(b->left, c, ok, type, rules);
4440 ###### propagate exec cases
4441 case Xcond_statement:
4443 // forpart and looppart->right must return Tnone
4444 // thenpart must return Tnone if there is a loopart,
4445 // otherwise it is like elsepart.
4447 // be bool if there is no casepart
4448 // match casepart->values if there is a switchpart
4449 // either be bool or match casepart->value if there
4451 // elsepart and casepart->action must match the return type
4452 // expected of this statement.
4453 struct cond_statement *cs = cast(cond_statement, prog);
4454 struct casepart *cp;
4456 t = propagate_types(cs->forpart, c, ok, Tnone, 0);
4457 if (!type_compat(Tnone, t, 0))
4458 *ok = 0; // UNTESTED
4461 t = propagate_types(cs->thenpart, c, ok, Tnone, 0);
4462 if (!type_compat(Tnone, t, 0))
4463 *ok = 0; // UNTESTED
4465 if (cs->casepart == NULL) {
4466 propagate_types(cs->condpart, c, ok, Tbool, 0);
4467 propagate_types(cs->looppart, c, ok, Tbool, 0);
4469 /* Condpart must match case values, with bool permitted */
4471 for (cp = cs->casepart;
4472 cp && !t; cp = cp->next)
4473 t = propagate_types(cp->value, c, ok, NULL, 0);
4474 if (!t && cs->condpart)
4475 t = propagate_types(cs->condpart, c, ok, NULL, Rboolok); // UNTESTED
4476 if (!t && cs->looppart)
4477 t = propagate_types(cs->looppart, c, ok, NULL, Rboolok); // UNTESTED
4478 // Now we have a type (I hope) push it down
4480 for (cp = cs->casepart; cp; cp = cp->next)
4481 propagate_types(cp->value, c, ok, t, 0);
4482 propagate_types(cs->condpart, c, ok, t, Rboolok);
4483 propagate_types(cs->looppart, c, ok, t, Rboolok);
4486 // (if)then, else, and case parts must return expected type.
4487 if (!cs->looppart && !type)
4488 type = propagate_types(cs->thenpart, c, ok, NULL, rules);
4490 type = propagate_types(cs->elsepart, c, ok, NULL, rules);
4491 for (cp = cs->casepart;
4493 cp = cp->next) // UNTESTED
4494 type = propagate_types(cp->action, c, ok, NULL, rules); // UNTESTED
4497 propagate_types(cs->thenpart, c, ok, type, rules);
4498 propagate_types(cs->elsepart, c, ok, type, rules);
4499 for (cp = cs->casepart; cp ; cp = cp->next)
4500 propagate_types(cp->action, c, ok, type, rules);
4506 ###### interp binode cases
4508 // This just performs one iterration of the loop
4509 rv = interp_exec(c, b->left, &rvtype);
4510 if (rvtype == Tnone ||
4511 (rvtype == Tbool && rv.bool != 0))
4512 // cnd is Tnone or Tbool, doesn't need to be freed
4513 interp_exec(c, b->right, NULL);
4516 ###### interp exec cases
4517 case Xcond_statement:
4519 struct value v, cnd;
4520 struct type *vtype, *cndtype;
4521 struct casepart *cp;
4522 struct cond_statement *cs = cast(cond_statement, e);
4525 interp_exec(c, cs->forpart, NULL);
4527 while ((cnd = interp_exec(c, cs->looppart, &cndtype)),
4528 cndtype == Tnone || (cndtype == Tbool && cnd.bool != 0))
4529 interp_exec(c, cs->thenpart, NULL);
4531 cnd = interp_exec(c, cs->condpart, &cndtype);
4532 if ((cndtype == Tnone ||
4533 (cndtype == Tbool && cnd.bool != 0))) {
4534 // cnd is Tnone or Tbool, doesn't need to be freed
4535 rv = interp_exec(c, cs->thenpart, &rvtype);
4536 // skip else (and cases)
4540 for (cp = cs->casepart; cp; cp = cp->next) {
4541 v = interp_exec(c, cp->value, &vtype);
4542 if (value_cmp(cndtype, vtype, &v, &cnd) == 0) {
4543 free_value(vtype, &v);
4544 free_value(cndtype, &cnd);
4545 rv = interp_exec(c, cp->action, &rvtype);
4548 free_value(vtype, &v);
4550 free_value(cndtype, &cnd);
4552 rv = interp_exec(c, cs->elsepart, &rvtype);
4559 ### Top level structure
4561 All the language elements so far can be used in various places. Now
4562 it is time to clarify what those places are.
4564 At the top level of a file there will be a number of declarations.
4565 Many of the things that can be declared haven't been described yet,
4566 such as functions, procedures, imports, and probably more.
4567 For now there are two sorts of things that can appear at the top
4568 level. They are predefined constants, `struct` types, and the `main`
4569 function. While the syntax will allow the `main` function to appear
4570 multiple times, that will trigger an error if it is actually attempted.
4572 The various declarations do not return anything. They store the
4573 various declarations in the parse context.
4575 ###### Parser: grammar
4578 Ocean -> OptNL DeclarationList
4580 ## declare terminals
4587 DeclarationList -> Declaration
4588 | DeclarationList Declaration
4590 Declaration -> ERROR Newlines ${
4591 tok_err(c, // UNTESTED
4592 "error: unhandled parse error", &$1);
4598 ## top level grammar
4602 ### The `const` section
4604 As well as being defined in with the code that uses them, constants
4605 can be declared at the top level. These have full-file scope, so they
4606 are always `InScope`. The value of a top level constant can be given
4607 as an expression, and this is evaluated immediately rather than in the
4608 later interpretation stage. Once we add functions to the language, we
4609 will need rules concern which, if any, can be used to define a top
4612 Constants are defined in a section that starts with the reserved word
4613 `const` and then has a block with a list of assignment statements.
4614 For syntactic consistency, these must use the double-colon syntax to
4615 make it clear that they are constants. Type can also be given: if
4616 not, the type will be determined during analysis, as with other
4619 As the types constants are inserted at the head of a list, printing
4620 them in the same order that they were read is not straight forward.
4621 We take a quadratic approach here and count the number of constants
4622 (variables of depth 0), then count down from there, each time
4623 searching through for the Nth constant for decreasing N.
4625 ###### top level grammar
4629 DeclareConstant -> const { IN OptNL ConstList OUT OptNL } Newlines
4630 | const { SimpleConstList } Newlines
4631 | const IN OptNL ConstList OUT Newlines
4632 | const SimpleConstList Newlines
4634 ConstList -> ConstList SimpleConstLine
4636 SimpleConstList -> SimpleConstList ; Const
4639 SimpleConstLine -> SimpleConstList Newlines
4640 | ERROR Newlines ${ tok_err(c, "Syntax error in constant", &$1); }$
4643 CType -> Type ${ $0 = $<1; }$
4646 Const -> IDENTIFIER :: CType = Expression ${ {
4650 v = var_decl(c, $1.txt);
4652 struct var *var = new_pos(var, $1);
4653 v->where_decl = var;
4658 v = var_ref(c, $1.txt);
4659 tok_err(c, "error: name already declared", &$1);
4660 type_err(c, "info: this is where '%v' was first declared",
4661 v->where_decl, NULL, 0, NULL);
4665 propagate_types($5, c, &ok, $3, 0);
4670 struct value res = interp_exec(c, $5, &v->type);
4671 global_alloc(c, v->type, v, &res);
4675 ###### print const decls
4680 while (target != 0) {
4682 for (v = context.in_scope; v; v=v->in_scope)
4683 if (v->depth == 0 && v->constant) {
4694 struct value *val = var_value(&context, v);
4695 printf(" %.*s :: ", v->name->name.len, v->name->name.txt);
4696 type_print(v->type, stdout);
4698 if (v->type == Tstr)
4700 print_value(v->type, val);
4701 if (v->type == Tstr)
4709 ### Function declarations
4711 The code in an Ocean program is all stored in function declarations.
4712 One of the functions must be named `main` and it must accept an array of
4713 strings as a parameter - the command line arguments.
4715 As this is the top level, several things are handled a bit
4717 The function is not interpreted by `interp_exec` as that isn't
4718 passed the argument list which the program requires. Similarly type
4719 analysis is a bit more interesting at this level.
4721 ###### ast functions
4723 static struct variable *declare_function(struct parse_context *c,
4724 struct variable *name,
4725 struct binode *args,
4728 struct text funcname = {" func", 5};
4730 struct value fn = {.function = code};
4731 name->type = add_type(c, funcname, &function_prototype);
4732 name->type->function.params = reorder_bilist(args);
4733 global_alloc(c, name->type, name, &fn);
4734 var_block_close(c, CloseSequential, code);
4736 var_block_close(c, CloseSequential, NULL);
4740 ###### top level grammar
4743 DeclareFunction -> func FuncName ( OpenScope ArgsLine ) Block Newlines ${
4744 $0 = declare_function(c, $<FN, $<Ar, $<Bl);
4746 | func FuncName IN OpenScope Args OUT OptNL do Block Newlines ${
4747 $0 = declare_function(c, $<FN, $<Ar, $<Bl);
4749 | func FuncName NEWLINE OpenScope OptNL do Block Newlines ${
4750 $0 = declare_function(c, $<FN, NULL, $<Bl);
4753 ###### print func decls
4758 while (target != 0) {
4760 for (v = context.in_scope; v; v=v->in_scope)
4761 if (v->depth == 0 && v->type && v->type->check_args) {
4770 struct value *val = var_value(&context, v);
4771 printf("func %.*s", v->name->name.len, v->name->name.txt);
4772 v->type->print_type_decl(v->type, stdout);
4774 print_exec(val->function, 0, brackets);
4776 print_value(v->type, val);
4777 printf("/* frame size %d */\n", v->type->function.local_size);
4783 ###### core functions
4785 static int analyse_funcs(struct parse_context *c)
4789 for (v = c->in_scope; v; v = v->in_scope) {
4792 if (v->depth != 0 || !v->type || !v->type->check_args)
4794 val = var_value(c, v);
4797 propagate_types(val->function, c, &ok, Tnone, 0);
4800 /* Make sure everything is still consistent */
4801 propagate_types(val->function, c, &ok, Tnone, 0);
4804 v->type->function.local_size = scope_finalize(c);
4809 static int analyse_main(struct type *type, struct parse_context *c)
4811 struct binode *bp = type->function.params;
4815 struct type *argv_type;
4816 struct text argv_type_name = { " argv", 5 };
4818 argv_type = add_type(c, argv_type_name, &array_prototype);
4819 argv_type->array.member = Tstr;
4820 argv_type->array.unspec = 1;
4822 for (b = bp; b; b = cast(binode, b->right)) {
4826 propagate_types(b->left, c, &ok, argv_type, 0);
4828 default: /* invalid */ // NOTEST
4829 propagate_types(b->left, c, &ok, Tnone, 0); // NOTEST
4835 return !c->parse_error;
4838 static void interp_main(struct parse_context *c, int argc, char **argv)
4840 struct value *progp = NULL;
4841 struct text main_name = { "main", 4 };
4842 struct variable *mainv;
4848 mainv = var_ref(c, main_name);
4850 progp = var_value(c, mainv);
4851 if (!progp || !progp->function) {
4852 fprintf(stderr, "oceani: no main function found.\n");
4856 if (!analyse_main(mainv->type, c)) {
4857 fprintf(stderr, "oceani: main has wrong type.\n");
4861 al = mainv->type->function.params;
4863 c->local_size = mainv->type->function.local_size;
4864 c->local = calloc(1, c->local_size);
4866 struct var *v = cast(var, al->left);
4867 struct value *vl = var_value(c, v->var);
4877 mpq_set_ui(argcq, argc, 1);
4878 memcpy(var_value(c, t->array.vsize), &argcq, sizeof(argcq));
4879 t->prepare_type(c, t, 0);
4880 array_init(v->var->type, vl);
4881 for (i = 0; i < argc; i++) {
4882 struct value *vl2 = vl->array + i * v->var->type->array.member->size;
4884 arg.str.txt = argv[i];
4885 arg.str.len = strlen(argv[i]);
4886 free_value(Tstr, vl2);
4887 dup_value(Tstr, &arg, vl2);
4891 al = cast(binode, al->right);
4893 v = interp_exec(c, progp->function, &vtype);
4894 free_value(vtype, &v);
4899 ###### ast functions
4900 void free_variable(struct variable *v)
4904 ## And now to test it out.
4906 Having a language requires having a "hello world" program. I'll
4907 provide a little more than that: a program that prints "Hello world"
4908 finds the GCD of two numbers, prints the first few elements of
4909 Fibonacci, performs a binary search for a number, and a few other
4910 things which will likely grow as the languages grows.
4912 ###### File: oceani.mk
4915 @echo "===== DEMO ====="
4916 ./oceani --section "demo: hello" oceani.mdc 55 33
4922 four ::= 2 + 2 ; five ::= 10/2
4923 const pie ::= "I like Pie";
4924 cake ::= "The cake is"
4932 func main(argv:[argc::]string)
4933 print "Hello World, what lovely oceans you have!"
4934 print "Are there", five, "?"
4935 print pi, pie, "but", cake
4937 A := $argv[1]; B := $argv[2]
4939 /* When a variable is defined in both branches of an 'if',
4940 * and used afterwards, the variables are merged.
4946 print "Is", A, "bigger than", B,"? ", bigger
4947 /* If a variable is not used after the 'if', no
4948 * merge happens, so types can be different
4951 double:string = "yes"
4952 print A, "is more than twice", B, "?", double
4955 print "double", B, "is", double
4960 if a > 0 and then b > 0:
4966 print "GCD of", A, "and", B,"is", a
4968 print a, "is not positive, cannot calculate GCD"
4970 print b, "is not positive, cannot calculate GCD"
4975 print "Fibonacci:", f1,f2,
4976 then togo = togo - 1
4984 /* Binary search... */
4989 mid := (lo + hi) / 2
5002 print "Yay, I found", target
5004 print "Closest I found was", lo
5009 // "middle square" PRNG. Not particularly good, but one my
5010 // Dad taught me - the first one I ever heard of.
5011 for i:=1; then i = i + 1; while i < size:
5012 n := list[i-1] * list[i-1]
5013 list[i] = (n / 100) % 10 000
5015 print "Before sort:",
5016 for i:=0; then i = i + 1; while i < size:
5020 for i := 1; then i=i+1; while i < size:
5021 for j:=i-1; then j=j-1; while j >= 0:
5022 if list[j] > list[j+1]:
5026 print " After sort:",
5027 for i:=0; then i = i + 1; while i < size:
5031 if 1 == 2 then print "yes"; else print "no"
5035 bob.alive = (bob.name == "Hello")
5036 print "bob", "is" if bob.alive else "isn't", "alive"