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);
2485 Args -> ArgsLine NEWLINE ${ $0 = $<AL; }$
2486 | Args ArgsLine NEWLINE ${ {
2487 struct binode *b = $<AL;
2488 struct binode **bp = &b;
2490 bp = (struct binode **)&(*bp)->left;
2495 ArgsLine -> ${ $0 = NULL; }$
2496 | Varlist ${ $0 = $<1; }$
2497 | Varlist ; ${ $0 = $<1; }$
2499 Varlist -> Varlist ; ArgDecl ${
2513 ArgDecl -> IDENTIFIER : FormalType ${ {
2514 struct variable *v = var_decl(c, $1.txt);
2520 ## Executables: the elements of code
2522 Each code element needs to be parsed, printed, analysed,
2523 interpreted, and freed. There are several, so let's just start with
2524 the easy ones and work our way up.
2528 We have already met values as separate objects. When manifest
2529 constants appear in the program text, that must result in an executable
2530 which has a constant value. So the `val` structure embeds a value in
2543 ###### ast functions
2544 struct val *new_val(struct type *T, struct token tk)
2546 struct val *v = new_pos(val, tk);
2557 $0 = new_val(Tbool, $1);
2561 $0 = new_val(Tbool, $1);
2565 $0 = new_val(Tnum, $1);
2568 if (number_parse($0->val.num, tail, $1.txt) == 0)
2569 mpq_init($0->val.num); // UNTESTED
2571 tok_err(c, "error: unsupported number suffix",
2576 $0 = new_val(Tstr, $1);
2579 string_parse(&$1, '\\', &$0->val.str, tail);
2581 tok_err(c, "error: unsupported string suffix",
2586 $0 = new_val(Tstr, $1);
2589 string_parse(&$1, '\\', &$0->val.str, tail);
2591 tok_err(c, "error: unsupported string suffix",
2596 ###### print exec cases
2599 struct val *v = cast(val, e);
2600 if (v->vtype == Tstr)
2602 print_value(v->vtype, &v->val);
2603 if (v->vtype == Tstr)
2608 ###### propagate exec cases
2611 struct val *val = cast(val, prog);
2612 if (!type_compat(type, val->vtype, rules))
2613 type_err(c, "error: expected %1%r found %2",
2614 prog, type, rules, val->vtype);
2618 ###### interp exec cases
2620 rvtype = cast(val, e)->vtype;
2621 dup_value(rvtype, &cast(val, e)->val, &rv);
2624 ###### ast functions
2625 static void free_val(struct val *v)
2628 free_value(v->vtype, &v->val);
2632 ###### free exec cases
2633 case Xval: free_val(cast(val, e)); break;
2635 ###### ast functions
2636 // Move all nodes from 'b' to 'rv', reversing their order.
2637 // In 'b' 'left' is a list, and 'right' is the last node.
2638 // In 'rv', left' is the first node and 'right' is a list.
2639 static struct binode *reorder_bilist(struct binode *b)
2641 struct binode *rv = NULL;
2644 struct exec *t = b->right;
2648 b = cast(binode, b->left);
2658 Just as we used a `val` to wrap a value into an `exec`, we similarly
2659 need a `var` to wrap a `variable` into an exec. While each `val`
2660 contained a copy of the value, each `var` holds a link to the variable
2661 because it really is the same variable no matter where it appears.
2662 When a variable is used, we need to remember to follow the `->merged`
2663 link to find the primary instance.
2671 struct variable *var;
2679 VariableDecl -> IDENTIFIER : ${ {
2680 struct variable *v = var_decl(c, $1.txt);
2681 $0 = new_pos(var, $1);
2686 v = var_ref(c, $1.txt);
2688 type_err(c, "error: variable '%v' redeclared",
2690 type_err(c, "info: this is where '%v' was first declared",
2691 v->where_decl, NULL, 0, NULL);
2694 | IDENTIFIER :: ${ {
2695 struct variable *v = var_decl(c, $1.txt);
2696 $0 = new_pos(var, $1);
2702 v = var_ref(c, $1.txt);
2704 type_err(c, "error: variable '%v' redeclared",
2706 type_err(c, "info: this is where '%v' was first declared",
2707 v->where_decl, NULL, 0, NULL);
2710 | IDENTIFIER : Type ${ {
2711 struct variable *v = var_decl(c, $1.txt);
2712 $0 = new_pos(var, $1);
2719 v = var_ref(c, $1.txt);
2721 type_err(c, "error: variable '%v' redeclared",
2723 type_err(c, "info: this is where '%v' was first declared",
2724 v->where_decl, NULL, 0, NULL);
2727 | IDENTIFIER :: Type ${ {
2728 struct variable *v = var_decl(c, $1.txt);
2729 $0 = new_pos(var, $1);
2737 v = var_ref(c, $1.txt);
2739 type_err(c, "error: variable '%v' redeclared",
2741 type_err(c, "info: this is where '%v' was first declared",
2742 v->where_decl, NULL, 0, NULL);
2747 Variable -> IDENTIFIER ${ {
2748 struct variable *v = var_ref(c, $1.txt);
2749 $0 = new_pos(var, $1);
2751 /* This might be a label - allocate a var just in case */
2752 v = var_decl(c, $1.txt);
2759 cast(var, $0)->var = v;
2763 ###### print exec cases
2766 struct var *v = cast(var, e);
2768 struct binding *b = v->var->name;
2769 printf("%.*s", b->name.len, b->name.txt);
2776 if (loc && loc->type == Xvar) {
2777 struct var *v = cast(var, loc);
2779 struct binding *b = v->var->name;
2780 fprintf(stderr, "%.*s", b->name.len, b->name.txt);
2782 fputs("???", stderr); // NOTEST
2784 fputs("NOTVAR", stderr);
2787 ###### propagate exec cases
2791 struct var *var = cast(var, prog);
2792 struct variable *v = var->var;
2794 type_err(c, "%d:BUG: no variable!!", prog, NULL, 0, NULL); // NOTEST
2795 return Tnone; // NOTEST
2798 if (v->constant && (rules & Rnoconstant)) {
2799 type_err(c, "error: Cannot assign to a constant: %v",
2800 prog, NULL, 0, NULL);
2801 type_err(c, "info: name was defined as a constant here",
2802 v->where_decl, NULL, 0, NULL);
2805 if (v->type == Tnone && v->where_decl == prog)
2806 type_err(c, "error: variable used but not declared: %v",
2807 prog, NULL, 0, NULL);
2808 if (v->type == NULL) {
2809 if (type && *ok != 0) {
2811 v->where_set = prog;
2816 if (!type_compat(type, v->type, rules)) {
2817 type_err(c, "error: expected %1%r but variable '%v' is %2", prog,
2818 type, rules, v->type);
2819 type_err(c, "info: this is where '%v' was set to %1", v->where_set,
2820 v->type, rules, NULL);
2827 ###### interp exec cases
2830 struct var *var = cast(var, e);
2831 struct variable *v = var->var;
2834 lrv = var_value(c, v);
2839 ###### ast functions
2841 static void free_var(struct var *v)
2846 ###### free exec cases
2847 case Xvar: free_var(cast(var, e)); break;
2849 ### Expressions: Conditional
2851 Our first user of the `binode` will be conditional expressions, which
2852 is a bit odd as they actually have three components. That will be
2853 handled by having 2 binodes for each expression. The conditional
2854 expression is the lowest precedence operator which is why we define it
2855 first - to start the precedence list.
2857 Conditional expressions are of the form "value `if` condition `else`
2858 other_value". They associate to the right, so everything to the right
2859 of `else` is part of an else value, while only a higher-precedence to
2860 the left of `if` is the if values. Between `if` and `else` there is no
2861 room for ambiguity, so a full conditional expression is allowed in
2873 Expression -> Expression if Expression else Expression $$ifelse ${ {
2874 struct binode *b1 = new(binode);
2875 struct binode *b2 = new(binode);
2884 ## expression grammar
2886 ###### print binode cases
2889 b2 = cast(binode, b->right);
2890 if (bracket) printf("(");
2891 print_exec(b2->left, -1, bracket);
2893 print_exec(b->left, -1, bracket);
2895 print_exec(b2->right, -1, bracket);
2896 if (bracket) printf(")");
2899 ###### propagate binode cases
2902 /* cond must be Tbool, others must match */
2903 struct binode *b2 = cast(binode, b->right);
2906 propagate_types(b->left, c, ok, Tbool, 0);
2907 t = propagate_types(b2->left, c, ok, type, Rnolabel);
2908 t2 = propagate_types(b2->right, c, ok, type ?: t, Rnolabel);
2912 ###### interp binode cases
2915 struct binode *b2 = cast(binode, b->right);
2916 left = interp_exec(c, b->left, <ype);
2918 rv = interp_exec(c, b2->left, &rvtype); // UNTESTED
2920 rv = interp_exec(c, b2->right, &rvtype);
2926 We take a brief detour, now that we have expressions, to describe lists
2927 of expressions. These will be needed for function parameters and
2928 possibly other situations. They seem generic enough to introduce here
2929 to be used elsewhere.
2931 And ExpressionList will use the `List` type of `binode`, building up at
2932 the end. And place where they are used will probably call
2933 `reorder_bilist()` to get a more normal first/next arrangement.
2935 ###### declare terminals
2938 `List` execs have no implicit semantics, so they are never propagated or
2939 interpreted. The can be printed as a comma separate list, which is how
2940 they are parsed. Note they are also used for function formal parameter
2941 lists. In that case a separate function is used to print them.
2943 ###### print binode cases
2947 print_exec(b->left, -1, bracket);
2950 b = cast(binode, b->right);
2954 ###### propagate binode cases
2955 case List: abort(); // NOTEST
2956 ###### interp binode cases
2957 case List: abort(); // NOTEST
2962 ExpressionList -> ExpressionList , Expression ${
2975 ### Expressions: Boolean
2977 The next class of expressions to use the `binode` will be Boolean
2978 expressions. "`and then`" and "`or else`" are similar to `and` and `or`
2979 have same corresponding precendence. The difference is that they don't
2980 evaluate the second expression if not necessary.
2989 ###### expr precedence
2994 ###### expression grammar
2995 | Expression or Expression ${ {
2996 struct binode *b = new(binode);
3002 | Expression or else Expression ${ {
3003 struct binode *b = new(binode);
3010 | Expression and Expression ${ {
3011 struct binode *b = new(binode);
3017 | Expression and then Expression ${ {
3018 struct binode *b = new(binode);
3025 | not Expression ${ {
3026 struct binode *b = new(binode);
3032 ###### print binode cases
3034 if (bracket) printf("(");
3035 print_exec(b->left, -1, bracket);
3037 print_exec(b->right, -1, bracket);
3038 if (bracket) printf(")");
3041 if (bracket) printf("(");
3042 print_exec(b->left, -1, bracket);
3043 printf(" and then ");
3044 print_exec(b->right, -1, bracket);
3045 if (bracket) printf(")");
3048 if (bracket) printf("(");
3049 print_exec(b->left, -1, bracket);
3051 print_exec(b->right, -1, bracket);
3052 if (bracket) printf(")");
3055 if (bracket) printf("(");
3056 print_exec(b->left, -1, bracket);
3057 printf(" or else ");
3058 print_exec(b->right, -1, bracket);
3059 if (bracket) printf(")");
3062 if (bracket) printf("(");
3064 print_exec(b->right, -1, bracket);
3065 if (bracket) printf(")");
3068 ###### propagate binode cases
3074 /* both must be Tbool, result is Tbool */
3075 propagate_types(b->left, c, ok, Tbool, 0);
3076 propagate_types(b->right, c, ok, Tbool, 0);
3077 if (type && type != Tbool)
3078 type_err(c, "error: %1 operation found where %2 expected", prog,
3082 ###### interp binode cases
3084 rv = interp_exec(c, b->left, &rvtype);
3085 right = interp_exec(c, b->right, &rtype);
3086 rv.bool = rv.bool && right.bool;
3089 rv = interp_exec(c, b->left, &rvtype);
3091 rv = interp_exec(c, b->right, NULL);
3094 rv = interp_exec(c, b->left, &rvtype);
3095 right = interp_exec(c, b->right, &rtype);
3096 rv.bool = rv.bool || right.bool;
3099 rv = interp_exec(c, b->left, &rvtype);
3101 rv = interp_exec(c, b->right, NULL);
3104 rv = interp_exec(c, b->right, &rvtype);
3108 ### Expressions: Comparison
3110 Of slightly higher precedence that Boolean expressions are Comparisons.
3111 A comparison takes arguments of any comparable type, but the two types
3114 To simplify the parsing we introduce an `eop` which can record an
3115 expression operator, and the `CMPop` non-terminal will match one of them.
3122 ###### ast functions
3123 static void free_eop(struct eop *e)
3137 ###### expr precedence
3138 $LEFT < > <= >= == != CMPop
3140 ###### expression grammar
3141 | Expression CMPop Expression ${ {
3142 struct binode *b = new(binode);
3152 CMPop -> < ${ $0.op = Less; }$
3153 | > ${ $0.op = Gtr; }$
3154 | <= ${ $0.op = LessEq; }$
3155 | >= ${ $0.op = GtrEq; }$
3156 | == ${ $0.op = Eql; }$
3157 | != ${ $0.op = NEql; }$
3159 ###### print binode cases
3167 if (bracket) printf("(");
3168 print_exec(b->left, -1, bracket);
3170 case Less: printf(" < "); break;
3171 case LessEq: printf(" <= "); break;
3172 case Gtr: printf(" > "); break;
3173 case GtrEq: printf(" >= "); break;
3174 case Eql: printf(" == "); break;
3175 case NEql: printf(" != "); break;
3176 default: abort(); // NOTEST
3178 print_exec(b->right, -1, bracket);
3179 if (bracket) printf(")");
3182 ###### propagate binode cases
3189 /* Both must match but not be labels, result is Tbool */
3190 t = propagate_types(b->left, c, ok, NULL, Rnolabel);
3192 propagate_types(b->right, c, ok, t, 0);
3194 t = propagate_types(b->right, c, ok, NULL, Rnolabel); // UNTESTED
3196 t = propagate_types(b->left, c, ok, t, 0); // UNTESTED
3198 if (!type_compat(type, Tbool, 0))
3199 type_err(c, "error: Comparison returns %1 but %2 expected", prog,
3200 Tbool, rules, type);
3203 ###### interp binode cases
3212 left = interp_exec(c, b->left, <ype);
3213 right = interp_exec(c, b->right, &rtype);
3214 cmp = value_cmp(ltype, rtype, &left, &right);
3217 case Less: rv.bool = cmp < 0; break;
3218 case LessEq: rv.bool = cmp <= 0; break;
3219 case Gtr: rv.bool = cmp > 0; break;
3220 case GtrEq: rv.bool = cmp >= 0; break;
3221 case Eql: rv.bool = cmp == 0; break;
3222 case NEql: rv.bool = cmp != 0; break;
3223 default: rv.bool = 0; break; // NOTEST
3228 ### Expressions: Arithmetic etc.
3230 The remaining expressions with the highest precedence are arithmetic,
3231 string concatenation, and string conversion. String concatenation
3232 (`++`) has the same precedence as multiplication and division, but lower
3235 String conversion is a temporary feature until I get a better type
3236 system. `$` is a prefix operator which expects a string and returns
3239 `+` and `-` are both infix and prefix operations (where they are
3240 absolute value and negation). These have different operator names.
3242 We also have a 'Bracket' operator which records where parentheses were
3243 found. This makes it easy to reproduce these when printing. Possibly I
3244 should only insert brackets were needed for precedence.
3254 ###### expr precedence
3260 ###### expression grammar
3261 | Expression Eop Expression ${ {
3262 struct binode *b = new(binode);
3269 | Expression Top Expression ${ {
3270 struct binode *b = new(binode);
3277 | ( Expression ) ${ {
3278 struct binode *b = new_pos(binode, $1);
3283 | Uop Expression ${ {
3284 struct binode *b = new(binode);
3289 | Value ${ $0 = $<1; }$
3290 | Variable ${ $0 = $<1; }$
3295 Eop -> + ${ $0.op = Plus; }$
3296 | - ${ $0.op = Minus; }$
3298 Uop -> + ${ $0.op = Absolute; }$
3299 | - ${ $0.op = Negate; }$
3300 | $ ${ $0.op = StringConv; }$
3302 Top -> * ${ $0.op = Times; }$
3303 | / ${ $0.op = Divide; }$
3304 | % ${ $0.op = Rem; }$
3305 | ++ ${ $0.op = Concat; }$
3307 ###### print binode cases
3314 if (bracket) printf("(");
3315 print_exec(b->left, indent, bracket);
3317 case Plus: fputs(" + ", stdout); break;
3318 case Minus: fputs(" - ", stdout); break;
3319 case Times: fputs(" * ", stdout); break;
3320 case Divide: fputs(" / ", stdout); break;
3321 case Rem: fputs(" % ", stdout); break;
3322 case Concat: fputs(" ++ ", stdout); break;
3323 default: abort(); // NOTEST
3325 print_exec(b->right, indent, bracket);
3326 if (bracket) printf(")");
3331 if (bracket) printf("(");
3333 case Absolute: fputs("+", stdout); break;
3334 case Negate: fputs("-", stdout); break;
3335 case StringConv: fputs("$", stdout); break;
3336 default: abort(); // NOTEST
3338 print_exec(b->right, indent, bracket);
3339 if (bracket) printf(")");
3343 print_exec(b->right, indent, bracket);
3347 ###### propagate binode cases
3353 /* both must be numbers, result is Tnum */
3356 /* as propagate_types ignores a NULL,
3357 * unary ops fit here too */
3358 propagate_types(b->left, c, ok, Tnum, 0);
3359 propagate_types(b->right, c, ok, Tnum, 0);
3360 if (!type_compat(type, Tnum, 0))
3361 type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
3366 /* both must be Tstr, result is Tstr */
3367 propagate_types(b->left, c, ok, Tstr, 0);
3368 propagate_types(b->right, c, ok, Tstr, 0);
3369 if (!type_compat(type, Tstr, 0))
3370 type_err(c, "error: Concat returns %1 but %2 expected", prog,
3375 /* op must be string, result is number */
3376 propagate_types(b->left, c, ok, Tstr, 0);
3377 if (!type_compat(type, Tnum, 0))
3378 type_err(c, // UNTESTED
3379 "error: Can only convert string to number, not %1",
3380 prog, type, 0, NULL);
3384 return propagate_types(b->right, c, ok, type, 0);
3386 ###### interp binode cases
3389 rv = interp_exec(c, b->left, &rvtype);
3390 right = interp_exec(c, b->right, &rtype);
3391 mpq_add(rv.num, rv.num, right.num);
3394 rv = interp_exec(c, b->left, &rvtype);
3395 right = interp_exec(c, b->right, &rtype);
3396 mpq_sub(rv.num, rv.num, right.num);
3399 rv = interp_exec(c, b->left, &rvtype);
3400 right = interp_exec(c, b->right, &rtype);
3401 mpq_mul(rv.num, rv.num, right.num);
3404 rv = interp_exec(c, b->left, &rvtype);
3405 right = interp_exec(c, b->right, &rtype);
3406 mpq_div(rv.num, rv.num, right.num);
3411 left = interp_exec(c, b->left, <ype);
3412 right = interp_exec(c, b->right, &rtype);
3413 mpz_init(l); mpz_init(r); mpz_init(rem);
3414 mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
3415 mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
3416 mpz_tdiv_r(rem, l, r);
3417 val_init(Tnum, &rv);
3418 mpq_set_z(rv.num, rem);
3419 mpz_clear(r); mpz_clear(l); mpz_clear(rem);
3424 rv = interp_exec(c, b->right, &rvtype);
3425 mpq_neg(rv.num, rv.num);
3428 rv = interp_exec(c, b->right, &rvtype);
3429 mpq_abs(rv.num, rv.num);
3432 rv = interp_exec(c, b->right, &rvtype);
3435 left = interp_exec(c, b->left, <ype);
3436 right = interp_exec(c, b->right, &rtype);
3438 rv.str = text_join(left.str, right.str);
3441 right = interp_exec(c, b->right, &rvtype);
3445 struct text tx = right.str;
3448 if (tx.txt[0] == '-') {
3449 neg = 1; // UNTESTED
3450 tx.txt++; // UNTESTED
3451 tx.len--; // UNTESTED
3453 if (number_parse(rv.num, tail, tx) == 0)
3454 mpq_init(rv.num); // UNTESTED
3456 mpq_neg(rv.num, rv.num); // UNTESTED
3458 printf("Unsupported suffix: %.*s\n", tx.len, tx.txt); // UNTESTED
3462 ###### value functions
3464 static struct text text_join(struct text a, struct text b)
3467 rv.len = a.len + b.len;
3468 rv.txt = malloc(rv.len);
3469 memcpy(rv.txt, a.txt, a.len);
3470 memcpy(rv.txt+a.len, b.txt, b.len);
3476 A function call can appear either as an expression or as a statement.
3477 As functions cannot yet return values, only the statement version will work.
3478 We use a new 'Funcall' binode type to link the function with a list of
3479 arguments, form with the 'List' nodes.
3484 ###### expression grammar
3485 | Variable ( ExpressionList ) ${ {
3486 struct binode *b = new(binode);
3489 b->right = reorder_bilist($<EL);
3493 struct binode *b = new(binode);
3500 ###### SimpleStatement Grammar
3502 | Variable ( ExpressionList ) ${ {
3503 struct binode *b = new(binode);
3506 b->right = reorder_bilist($<EL);
3510 ###### print binode cases
3513 do_indent(indent, "");
3514 print_exec(b->left, -1, bracket);
3516 for (b = cast(binode, b->right); b; b = cast(binode, b->right)) {
3519 print_exec(b->left, -1, bracket);
3529 ###### propagate binode cases
3532 /* Every arg must match formal parameter, and result
3533 * is return type of function (currently Tnone).
3535 struct binode *args = cast(binode, b->right);
3536 struct var *v = cast(var, b->left);
3538 if (!v->var->type || v->var->type->check_args == NULL) {
3539 type_err(c, "error: attempt to call a non-function.",
3540 prog, NULL, 0, NULL);
3543 v->var->type->check_args(c, ok, v->var->type, args);
3547 ###### interp binode cases
3550 struct var *v = cast(var, b->left);
3551 struct type *t = v->var->type;
3552 void *oldlocal = c->local;
3553 int old_size = c->local_size;
3554 void *local = calloc(1, t->function.local_size);
3555 struct value *fbody = var_value(c, v->var);
3556 struct binode *arg = cast(binode, b->right);
3557 struct binode *param = t->function.params;
3560 struct var *pv = cast(var, param->left);
3561 struct type *vtype = NULL;
3562 struct value val = interp_exec(c, arg->left, &vtype);
3564 c->local = local; c->local_size = t->function.local_size;
3565 lval = var_value(c, pv->var);
3566 c->local = oldlocal; c->local_size = old_size;
3567 memcpy(lval, &val, vtype->size);
3568 param = cast(binode, param->right);
3569 arg = cast(binode, arg->right);
3571 c->local = local; c->local_size = t->function.local_size;
3572 right = interp_exec(c, fbody->function, &rtype);
3573 c->local = oldlocal; c->local_size = old_size;
3578 ### Blocks, Statements, and Statement lists.
3580 Now that we have expressions out of the way we need to turn to
3581 statements. There are simple statements and more complex statements.
3582 Simple statements do not contain (syntactic) newlines, complex statements do.
3584 Statements often come in sequences and we have corresponding simple
3585 statement lists and complex statement lists.
3586 The former comprise only simple statements separated by semicolons.
3587 The later comprise complex statements and simple statement lists. They are
3588 separated by newlines. Thus the semicolon is only used to separate
3589 simple statements on the one line. This may be overly restrictive,
3590 but I'm not sure I ever want a complex statement to share a line with
3593 Note that a simple statement list can still use multiple lines if
3594 subsequent lines are indented, so
3596 ###### Example: wrapped simple statement list
3601 is a single simple statement list. This might allow room for
3602 confusion, so I'm not set on it yet.
3604 A simple statement list needs no extra syntax. A complex statement
3605 list has two syntactic forms. It can be enclosed in braces (much like
3606 C blocks), or it can be introduced by an indent and continue until an
3607 unindented newline (much like Python blocks). With this extra syntax
3608 it is referred to as a block.
3610 Note that a block does not have to include any newlines if it only
3611 contains simple statements. So both of:
3613 if condition: a=b; d=f
3615 if condition { a=b; print f }
3619 In either case the list is constructed from a `binode` list with
3620 `Block` as the operator. When parsing the list it is most convenient
3621 to append to the end, so a list is a list and a statement. When using
3622 the list it is more convenient to consider a list to be a statement
3623 and a list. So we need a function to re-order a list.
3624 `reorder_bilist` serves this purpose.
3626 The only stand-alone statement we introduce at this stage is `pass`
3627 which does nothing and is represented as a `NULL` pointer in a `Block`
3628 list. Other stand-alone statements will follow once the infrastructure
3639 Block -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3640 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3641 | SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3642 | SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3643 | IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3645 OpenBlock -> OpenScope { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3646 | OpenScope { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3647 | OpenScope SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3648 | OpenScope SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3649 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3651 UseBlock -> { OpenScope IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3652 | { OpenScope SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3653 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3655 ColonBlock -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3656 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3657 | : SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3658 | : SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3659 | : IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3661 Statementlist -> ComplexStatements ${ $0 = reorder_bilist($<CS); }$
3663 ComplexStatements -> ComplexStatements ComplexStatement ${
3673 | ComplexStatement ${
3685 ComplexStatement -> SimpleStatements Newlines ${
3686 $0 = reorder_bilist($<SS);
3688 | SimpleStatements ; Newlines ${
3689 $0 = reorder_bilist($<SS);
3691 ## ComplexStatement Grammar
3694 SimpleStatements -> SimpleStatements ; SimpleStatement ${
3700 | SimpleStatement ${
3708 SimpleStatement -> pass ${ $0 = NULL; }$
3709 | ERROR ${ tok_err(c, "Syntax error in statement", &$1); }$
3710 ## SimpleStatement Grammar
3712 ###### print binode cases
3716 if (b->left == NULL) // UNTESTED
3717 printf("pass"); // UNTESTED
3719 print_exec(b->left, indent, bracket); // UNTESTED
3720 if (b->right) { // UNTESTED
3721 printf("; "); // UNTESTED
3722 print_exec(b->right, indent, bracket); // UNTESTED
3725 // block, one per line
3726 if (b->left == NULL)
3727 do_indent(indent, "pass\n");
3729 print_exec(b->left, indent, bracket);
3731 print_exec(b->right, indent, bracket);
3735 ###### propagate binode cases
3738 /* If any statement returns something other than Tnone
3739 * or Tbool then all such must return same type.
3740 * As each statement may be Tnone or something else,
3741 * we must always pass NULL (unknown) down, otherwise an incorrect
3742 * error might occur. We never return Tnone unless it is
3747 for (e = b; e; e = cast(binode, e->right)) {
3748 t = propagate_types(e->left, c, ok, NULL, rules);
3749 if ((rules & Rboolok) && (t == Tbool || t == Tnone))
3751 if (t == Tnone && e->right)
3752 /* Only the final statement *must* return a value
3760 type_err(c, "error: expected %1%r, found %2",
3761 e->left, type, rules, t);
3767 ###### interp binode cases
3769 while (rvtype == Tnone &&
3772 rv = interp_exec(c, b->left, &rvtype);
3773 b = cast(binode, b->right);
3777 ### The Print statement
3779 `print` is a simple statement that takes a comma-separated list of
3780 expressions and prints the values separated by spaces and terminated
3781 by a newline. No control of formatting is possible.
3783 `print` uses `ExpressionList` to collect the expressions and stores them
3784 on the left side of a `Print` binode unlessthere is a trailing comma
3785 when the list is stored on the `right` side and no trailing newline is
3791 ##### expr precedence
3794 ###### SimpleStatement Grammar
3796 | print ExpressionList ${
3800 $0->left = reorder_bilist($<EL);
3802 | print ExpressionList , ${ {
3805 $0->right = reorder_bilist($<EL);
3815 ###### print binode cases
3818 do_indent(indent, "print");
3820 print_exec(b->right, -1, bracket);
3823 print_exec(b->left, -1, bracket);
3828 ###### propagate binode cases
3831 /* don't care but all must be consistent */
3833 b = cast(binode, b->left);
3835 b = cast(binode, b->right);
3837 propagate_types(b->left, c, ok, NULL, Rnolabel);
3838 b = cast(binode, b->right);
3842 ###### interp binode cases
3846 struct binode *b2 = cast(binode, b->left);
3848 b2 = cast(binode, b->right);
3849 for (; b2; b2 = cast(binode, b2->right)) {
3850 left = interp_exec(c, b2->left, <ype);
3851 print_value(ltype, &left);
3852 free_value(ltype, &left);
3856 if (b->right == NULL)
3862 ###### Assignment statement
3864 An assignment will assign a value to a variable, providing it hasn't
3865 been declared as a constant. The analysis phase ensures that the type
3866 will be correct so the interpreter just needs to perform the
3867 calculation. There is a form of assignment which declares a new
3868 variable as well as assigning a value. If a name is assigned before
3869 it is declared, and error will be raised as the name is created as
3870 `Tlabel` and it is illegal to assign to such names.
3876 ###### declare terminals
3879 ###### SimpleStatement Grammar
3880 | Variable = Expression ${
3886 | VariableDecl = Expression ${
3894 if ($1->var->where_set == NULL) {
3896 "Variable declared with no type or value: %v",
3906 ###### print binode cases
3909 do_indent(indent, "");
3910 print_exec(b->left, indent, bracket);
3912 print_exec(b->right, indent, bracket);
3919 struct variable *v = cast(var, b->left)->var;
3920 do_indent(indent, "");
3921 print_exec(b->left, indent, bracket);
3922 if (cast(var, b->left)->var->constant) {
3924 if (v->where_decl == v->where_set) {
3925 type_print(v->type, stdout);
3930 if (v->where_decl == v->where_set) {
3931 type_print(v->type, stdout);
3937 print_exec(b->right, indent, bracket);
3944 ###### propagate binode cases
3948 /* Both must match and not be labels,
3949 * Type must support 'dup',
3950 * For Assign, left must not be constant.
3953 t = propagate_types(b->left, c, ok, NULL,
3954 Rnolabel | (b->op == Assign ? Rnoconstant : 0));
3959 if (propagate_types(b->right, c, ok, t, 0) != t)
3960 if (b->left->type == Xvar)
3961 type_err(c, "info: variable '%v' was set as %1 here.",
3962 cast(var, b->left)->var->where_set, t, rules, NULL);
3964 t = propagate_types(b->right, c, ok, NULL, Rnolabel);
3966 propagate_types(b->left, c, ok, t,
3967 (b->op == Assign ? Rnoconstant : 0));
3969 if (t && t->dup == NULL)
3970 type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
3975 ###### interp binode cases
3978 lleft = linterp_exec(c, b->left, <ype);
3979 right = interp_exec(c, b->right, &rtype);
3981 free_value(ltype, lleft);
3982 dup_value(ltype, &right, lleft);
3989 struct variable *v = cast(var, b->left)->var;
3992 val = var_value(c, v);
3993 if (v->type->prepare_type)
3994 v->type->prepare_type(c, v->type, 0);
3996 right = interp_exec(c, b->right, &rtype);
3997 memcpy(val, &right, rtype->size);
4000 val_init(v->type, val);
4005 ### The `use` statement
4007 The `use` statement is the last "simple" statement. It is needed when
4008 the condition in a conditional statement is a block. `use` works much
4009 like `return` in C, but only completes the `condition`, not the whole
4015 ###### expr precedence
4018 ###### SimpleStatement Grammar
4020 $0 = new_pos(binode, $1);
4023 if ($0->right->type == Xvar) {
4024 struct var *v = cast(var, $0->right);
4025 if (v->var->type == Tnone) {
4026 /* Convert this to a label */
4029 v->var->type = Tlabel;
4030 val = global_alloc(c, Tlabel, v->var, NULL);
4036 ###### print binode cases
4039 do_indent(indent, "use ");
4040 print_exec(b->right, -1, bracket);
4045 ###### propagate binode cases
4048 /* result matches value */
4049 return propagate_types(b->right, c, ok, type, 0);
4051 ###### interp binode cases
4054 rv = interp_exec(c, b->right, &rvtype);
4057 ### The Conditional Statement
4059 This is the biggy and currently the only complex statement. This
4060 subsumes `if`, `while`, `do/while`, `switch`, and some parts of `for`.
4061 It is comprised of a number of parts, all of which are optional though
4062 set combinations apply. Each part is (usually) a key word (`then` is
4063 sometimes optional) followed by either an expression or a code block,
4064 except the `casepart` which is a "key word and an expression" followed
4065 by a code block. The code-block option is valid for all parts and,
4066 where an expression is also allowed, the code block can use the `use`
4067 statement to report a value. If the code block does not report a value
4068 the effect is similar to reporting `True`.
4070 The `else` and `case` parts, as well as `then` when combined with
4071 `if`, can contain a `use` statement which will apply to some
4072 containing conditional statement. `for` parts, `do` parts and `then`
4073 parts used with `for` can never contain a `use`, except in some
4074 subordinate conditional statement.
4076 If there is a `forpart`, it is executed first, only once.
4077 If there is a `dopart`, then it is executed repeatedly providing
4078 always that the `condpart` or `cond`, if present, does not return a non-True
4079 value. `condpart` can fail to return any value if it simply executes
4080 to completion. This is treated the same as returning `True`.
4082 If there is a `thenpart` it will be executed whenever the `condpart`
4083 or `cond` returns True (or does not return any value), but this will happen
4084 *after* `dopart` (when present).
4086 If `elsepart` is present it will be executed at most once when the
4087 condition returns `False` or some value that isn't `True` and isn't
4088 matched by any `casepart`. If there are any `casepart`s, they will be
4089 executed when the condition returns a matching value.
4091 The particular sorts of values allowed in case parts has not yet been
4092 determined in the language design, so nothing is prohibited.
4094 The various blocks in this complex statement potentially provide scope
4095 for variables as described earlier. Each such block must include the
4096 "OpenScope" nonterminal before parsing the block, and must call
4097 `var_block_close()` when closing the block.
4099 The code following "`if`", "`switch`" and "`for`" does not get its own
4100 scope, but is in a scope covering the whole statement, so names
4101 declared there cannot be redeclared elsewhere. Similarly the
4102 condition following "`while`" is in a scope the covers the body
4103 ("`do`" part) of the loop, and which does not allow conditional scope
4104 extension. Code following "`then`" (both looping and non-looping),
4105 "`else`" and "`case`" each get their own local scope.
4107 The type requirements on the code block in a `whilepart` are quite
4108 unusal. It is allowed to return a value of some identifiable type, in
4109 which case the loop aborts and an appropriate `casepart` is run, or it
4110 can return a Boolean, in which case the loop either continues to the
4111 `dopart` (on `True`) or aborts and runs the `elsepart` (on `False`).
4112 This is different both from the `ifpart` code block which is expected to
4113 return a Boolean, or the `switchpart` code block which is expected to
4114 return the same type as the casepart values. The correct analysis of
4115 the type of the `whilepart` code block is the reason for the
4116 `Rboolok` flag which is passed to `propagate_types()`.
4118 The `cond_statement` cannot fit into a `binode` so a new `exec` is
4119 defined. As there are two scopes which cover multiple parts - one for
4120 the whole statement and one for "while" and "do" - and as we will use
4121 the 'struct exec' to track scopes, we actually need two new types of
4122 exec. One is a `binode` for the looping part, the rest is the
4123 `cond_statement`. The `cond_statement` will use an auxilliary `struct
4124 casepart` to track a list of case parts.
4135 struct exec *action;
4136 struct casepart *next;
4138 struct cond_statement {
4140 struct exec *forpart, *condpart, *thenpart, *elsepart;
4141 struct binode *looppart;
4142 struct casepart *casepart;
4145 ###### ast functions
4147 static void free_casepart(struct casepart *cp)
4151 free_exec(cp->value);
4152 free_exec(cp->action);
4159 static void free_cond_statement(struct cond_statement *s)
4163 free_exec(s->forpart);
4164 free_exec(s->condpart);
4165 free_exec(s->looppart);
4166 free_exec(s->thenpart);
4167 free_exec(s->elsepart);
4168 free_casepart(s->casepart);
4172 ###### free exec cases
4173 case Xcond_statement: free_cond_statement(cast(cond_statement, e)); break;
4175 ###### ComplexStatement Grammar
4176 | CondStatement ${ $0 = $<1; }$
4178 ###### expr precedence
4179 $TERM for then while do
4186 // A CondStatement must end with EOL, as does CondSuffix and
4188 // ForPart, ThenPart, SwitchPart, CasePart are non-empty and
4189 // may or may not end with EOL
4190 // WhilePart and IfPart include an appropriate Suffix
4192 // ForPart, SwitchPart, and IfPart open scopes, o we have to close
4193 // them. WhilePart opens and closes its own scope.
4194 CondStatement -> ForPart OptNL ThenPart OptNL WhilePart CondSuffix ${
4197 $0->thenpart = $<TP;
4198 $0->looppart = $<WP;
4199 var_block_close(c, CloseSequential, $0);
4201 | ForPart OptNL WhilePart CondSuffix ${
4204 $0->looppart = $<WP;
4205 var_block_close(c, CloseSequential, $0);
4207 | WhilePart CondSuffix ${
4209 $0->looppart = $<WP;
4211 | SwitchPart OptNL CasePart CondSuffix ${
4213 $0->condpart = $<SP;
4214 $CP->next = $0->casepart;
4215 $0->casepart = $<CP;
4216 var_block_close(c, CloseSequential, $0);
4218 | SwitchPart : IN OptNL CasePart CondSuffix OUT Newlines ${
4220 $0->condpart = $<SP;
4221 $CP->next = $0->casepart;
4222 $0->casepart = $<CP;
4223 var_block_close(c, CloseSequential, $0);
4225 | IfPart IfSuffix ${
4227 $0->condpart = $IP.condpart; $IP.condpart = NULL;
4228 $0->thenpart = $IP.thenpart; $IP.thenpart = NULL;
4229 // This is where we close an "if" statement
4230 var_block_close(c, CloseSequential, $0);
4233 CondSuffix -> IfSuffix ${
4236 | Newlines CasePart CondSuffix ${
4238 $CP->next = $0->casepart;
4239 $0->casepart = $<CP;
4241 | CasePart CondSuffix ${
4243 $CP->next = $0->casepart;
4244 $0->casepart = $<CP;
4247 IfSuffix -> Newlines ${ $0 = new(cond_statement); }$
4248 | Newlines ElsePart ${ $0 = $<EP; }$
4249 | ElsePart ${$0 = $<EP; }$
4251 ElsePart -> else OpenBlock Newlines ${
4252 $0 = new(cond_statement);
4253 $0->elsepart = $<OB;
4254 var_block_close(c, CloseElse, $0->elsepart);
4256 | else OpenScope CondStatement ${
4257 $0 = new(cond_statement);
4258 $0->elsepart = $<CS;
4259 var_block_close(c, CloseElse, $0->elsepart);
4263 CasePart -> case Expression OpenScope ColonBlock ${
4264 $0 = calloc(1,sizeof(struct casepart));
4267 var_block_close(c, CloseParallel, $0->action);
4271 // These scopes are closed in CondStatement
4272 ForPart -> for OpenBlock ${
4276 ThenPart -> then OpenBlock ${
4278 var_block_close(c, CloseSequential, $0);
4282 // This scope is closed in CondStatement
4283 WhilePart -> while UseBlock OptNL do OpenBlock ${
4288 var_block_close(c, CloseSequential, $0->right);
4289 var_block_close(c, CloseSequential, $0);
4291 | while OpenScope Expression OpenScope ColonBlock ${
4296 var_block_close(c, CloseSequential, $0->right);
4297 var_block_close(c, CloseSequential, $0);
4301 IfPart -> if UseBlock OptNL then OpenBlock ${
4304 var_block_close(c, CloseParallel, $0.thenpart);
4306 | if OpenScope Expression OpenScope ColonBlock ${
4309 var_block_close(c, CloseParallel, $0.thenpart);
4311 | if OpenScope Expression OpenScope OptNL then Block ${
4314 var_block_close(c, CloseParallel, $0.thenpart);
4318 // This scope is closed in CondStatement
4319 SwitchPart -> switch OpenScope Expression ${
4322 | switch UseBlock ${
4326 ###### print binode cases
4328 if (b->left && b->left->type == Xbinode &&
4329 cast(binode, b->left)->op == Block) {
4331 do_indent(indent, "while {\n");
4333 do_indent(indent, "while\n");
4334 print_exec(b->left, indent+1, bracket);
4336 do_indent(indent, "} do {\n");
4338 do_indent(indent, "do\n");
4339 print_exec(b->right, indent+1, bracket);
4341 do_indent(indent, "}\n");
4343 do_indent(indent, "while ");
4344 print_exec(b->left, 0, bracket);
4349 print_exec(b->right, indent+1, bracket);
4351 do_indent(indent, "}\n");
4355 ###### print exec cases
4357 case Xcond_statement:
4359 struct cond_statement *cs = cast(cond_statement, e);
4360 struct casepart *cp;
4362 do_indent(indent, "for");
4363 if (bracket) printf(" {\n"); else printf("\n");
4364 print_exec(cs->forpart, indent+1, bracket);
4367 do_indent(indent, "} then {\n");
4369 do_indent(indent, "then\n");
4370 print_exec(cs->thenpart, indent+1, bracket);
4372 if (bracket) do_indent(indent, "}\n");
4375 print_exec(cs->looppart, indent, bracket);
4379 do_indent(indent, "switch");
4381 do_indent(indent, "if");
4382 if (cs->condpart && cs->condpart->type == Xbinode &&
4383 cast(binode, cs->condpart)->op == Block) {
4388 print_exec(cs->condpart, indent+1, bracket);
4390 do_indent(indent, "}\n");
4392 do_indent(indent, "then\n");
4393 print_exec(cs->thenpart, indent+1, bracket);
4397 print_exec(cs->condpart, 0, bracket);
4403 print_exec(cs->thenpart, indent+1, bracket);
4405 do_indent(indent, "}\n");
4410 for (cp = cs->casepart; cp; cp = cp->next) {
4411 do_indent(indent, "case ");
4412 print_exec(cp->value, -1, 0);
4417 print_exec(cp->action, indent+1, bracket);
4419 do_indent(indent, "}\n");
4422 do_indent(indent, "else");
4427 print_exec(cs->elsepart, indent+1, bracket);
4429 do_indent(indent, "}\n");
4434 ###### propagate binode cases
4436 t = propagate_types(b->right, c, ok, Tnone, 0);
4437 if (!type_compat(Tnone, t, 0))
4438 *ok = 0; // UNTESTED
4439 return propagate_types(b->left, c, ok, type, rules);
4441 ###### propagate exec cases
4442 case Xcond_statement:
4444 // forpart and looppart->right must return Tnone
4445 // thenpart must return Tnone if there is a loopart,
4446 // otherwise it is like elsepart.
4448 // be bool if there is no casepart
4449 // match casepart->values if there is a switchpart
4450 // either be bool or match casepart->value if there
4452 // elsepart and casepart->action must match the return type
4453 // expected of this statement.
4454 struct cond_statement *cs = cast(cond_statement, prog);
4455 struct casepart *cp;
4457 t = propagate_types(cs->forpart, c, ok, Tnone, 0);
4458 if (!type_compat(Tnone, t, 0))
4459 *ok = 0; // UNTESTED
4462 t = propagate_types(cs->thenpart, c, ok, Tnone, 0);
4463 if (!type_compat(Tnone, t, 0))
4464 *ok = 0; // UNTESTED
4466 if (cs->casepart == NULL) {
4467 propagate_types(cs->condpart, c, ok, Tbool, 0);
4468 propagate_types(cs->looppart, c, ok, Tbool, 0);
4470 /* Condpart must match case values, with bool permitted */
4472 for (cp = cs->casepart;
4473 cp && !t; cp = cp->next)
4474 t = propagate_types(cp->value, c, ok, NULL, 0);
4475 if (!t && cs->condpart)
4476 t = propagate_types(cs->condpart, c, ok, NULL, Rboolok); // UNTESTED
4477 if (!t && cs->looppart)
4478 t = propagate_types(cs->looppart, c, ok, NULL, Rboolok); // UNTESTED
4479 // Now we have a type (I hope) push it down
4481 for (cp = cs->casepart; cp; cp = cp->next)
4482 propagate_types(cp->value, c, ok, t, 0);
4483 propagate_types(cs->condpart, c, ok, t, Rboolok);
4484 propagate_types(cs->looppart, c, ok, t, Rboolok);
4487 // (if)then, else, and case parts must return expected type.
4488 if (!cs->looppart && !type)
4489 type = propagate_types(cs->thenpart, c, ok, NULL, rules);
4491 type = propagate_types(cs->elsepart, c, ok, NULL, rules);
4492 for (cp = cs->casepart;
4494 cp = cp->next) // UNTESTED
4495 type = propagate_types(cp->action, c, ok, NULL, rules); // UNTESTED
4498 propagate_types(cs->thenpart, c, ok, type, rules);
4499 propagate_types(cs->elsepart, c, ok, type, rules);
4500 for (cp = cs->casepart; cp ; cp = cp->next)
4501 propagate_types(cp->action, c, ok, type, rules);
4507 ###### interp binode cases
4509 // This just performs one iterration of the loop
4510 rv = interp_exec(c, b->left, &rvtype);
4511 if (rvtype == Tnone ||
4512 (rvtype == Tbool && rv.bool != 0))
4513 // cnd is Tnone or Tbool, doesn't need to be freed
4514 interp_exec(c, b->right, NULL);
4517 ###### interp exec cases
4518 case Xcond_statement:
4520 struct value v, cnd;
4521 struct type *vtype, *cndtype;
4522 struct casepart *cp;
4523 struct cond_statement *cs = cast(cond_statement, e);
4526 interp_exec(c, cs->forpart, NULL);
4528 while ((cnd = interp_exec(c, cs->looppart, &cndtype)),
4529 cndtype == Tnone || (cndtype == Tbool && cnd.bool != 0))
4530 interp_exec(c, cs->thenpart, NULL);
4532 cnd = interp_exec(c, cs->condpart, &cndtype);
4533 if ((cndtype == Tnone ||
4534 (cndtype == Tbool && cnd.bool != 0))) {
4535 // cnd is Tnone or Tbool, doesn't need to be freed
4536 rv = interp_exec(c, cs->thenpart, &rvtype);
4537 // skip else (and cases)
4541 for (cp = cs->casepart; cp; cp = cp->next) {
4542 v = interp_exec(c, cp->value, &vtype);
4543 if (value_cmp(cndtype, vtype, &v, &cnd) == 0) {
4544 free_value(vtype, &v);
4545 free_value(cndtype, &cnd);
4546 rv = interp_exec(c, cp->action, &rvtype);
4549 free_value(vtype, &v);
4551 free_value(cndtype, &cnd);
4553 rv = interp_exec(c, cs->elsepart, &rvtype);
4560 ### Top level structure
4562 All the language elements so far can be used in various places. Now
4563 it is time to clarify what those places are.
4565 At the top level of a file there will be a number of declarations.
4566 Many of the things that can be declared haven't been described yet,
4567 such as functions, procedures, imports, and probably more.
4568 For now there are two sorts of things that can appear at the top
4569 level. They are predefined constants, `struct` types, and the `main`
4570 function. While the syntax will allow the `main` function to appear
4571 multiple times, that will trigger an error if it is actually attempted.
4573 The various declarations do not return anything. They store the
4574 various declarations in the parse context.
4576 ###### Parser: grammar
4579 Ocean -> OptNL DeclarationList
4581 ## declare terminals
4588 DeclarationList -> Declaration
4589 | DeclarationList Declaration
4591 Declaration -> ERROR Newlines ${
4592 tok_err(c, // UNTESTED
4593 "error: unhandled parse error", &$1);
4599 ## top level grammar
4603 ### The `const` section
4605 As well as being defined in with the code that uses them, constants
4606 can be declared at the top level. These have full-file scope, so they
4607 are always `InScope`. The value of a top level constant can be given
4608 as an expression, and this is evaluated immediately rather than in the
4609 later interpretation stage. Once we add functions to the language, we
4610 will need rules concern which, if any, can be used to define a top
4613 Constants are defined in a section that starts with the reserved word
4614 `const` and then has a block with a list of assignment statements.
4615 For syntactic consistency, these must use the double-colon syntax to
4616 make it clear that they are constants. Type can also be given: if
4617 not, the type will be determined during analysis, as with other
4620 As the types constants are inserted at the head of a list, printing
4621 them in the same order that they were read is not straight forward.
4622 We take a quadratic approach here and count the number of constants
4623 (variables of depth 0), then count down from there, each time
4624 searching through for the Nth constant for decreasing N.
4626 ###### top level grammar
4630 DeclareConstant -> const { IN OptNL ConstList OUT OptNL } Newlines
4631 | const { SimpleConstList } Newlines
4632 | const IN OptNL ConstList OUT Newlines
4633 | const SimpleConstList Newlines
4635 ConstList -> ConstList SimpleConstLine
4637 SimpleConstList -> SimpleConstList ; Const
4640 SimpleConstLine -> SimpleConstList Newlines
4641 | ERROR Newlines ${ tok_err(c, "Syntax error in constant", &$1); }$
4644 CType -> Type ${ $0 = $<1; }$
4647 Const -> IDENTIFIER :: CType = Expression ${ {
4651 v = var_decl(c, $1.txt);
4653 struct var *var = new_pos(var, $1);
4654 v->where_decl = var;
4659 v = var_ref(c, $1.txt);
4660 tok_err(c, "error: name already declared", &$1);
4661 type_err(c, "info: this is where '%v' was first declared",
4662 v->where_decl, NULL, 0, NULL);
4666 propagate_types($5, c, &ok, $3, 0);
4671 struct value res = interp_exec(c, $5, &v->type);
4672 global_alloc(c, v->type, v, &res);
4676 ###### print const decls
4681 while (target != 0) {
4683 for (v = context.in_scope; v; v=v->in_scope)
4684 if (v->depth == 0 && v->constant) {
4695 struct value *val = var_value(&context, v);
4696 printf(" %.*s :: ", v->name->name.len, v->name->name.txt);
4697 type_print(v->type, stdout);
4699 if (v->type == Tstr)
4701 print_value(v->type, val);
4702 if (v->type == Tstr)
4710 ### Function declarations
4712 The code in an Ocean program is all stored in function declarations.
4713 One of the functions must be named `main` and it must accept an array of
4714 strings as a parameter - the command line arguments.
4717 As this is the top level, several things are handled a bit
4719 The function is not interpreted by `interp_exec` as that isn't
4720 passed the argument list which the program requires. Similarly type
4721 analysis is a bit more interesting at this level.
4723 ###### ast functions
4725 static struct variable *declare_function(struct parse_context *c,
4726 struct variable *name,
4727 struct binode *args,
4730 struct text funcname = {" func", 5};
4732 struct value fn = {.function = code};
4733 name->type = add_type(c, funcname, &function_prototype);
4734 name->type->function.params = reorder_bilist(args);
4735 global_alloc(c, name->type, name, &fn);
4736 var_block_close(c, CloseSequential, code);
4738 var_block_close(c, CloseSequential, NULL);
4742 ###### top level grammar
4745 DeclareFunction -> func FuncName ( OpenScope ArgsLine ) Block Newlines ${
4746 $0 = declare_function(c, $<FN, $<Ar, $<Bl);
4748 | func FuncName IN OpenScope Args OUT OptNL do Block Newlines ${
4749 $0 = declare_function(c, $<FN, $<Ar, $<Bl);
4751 | func FuncName NEWLINE OpenScope OptNL do Block Newlines ${
4752 $0 = declare_function(c, $<FN, NULL, $<Bl);
4755 ###### print func decls
4760 while (target != 0) {
4762 for (v = context.in_scope; v; v=v->in_scope)
4763 if (v->depth == 0 && v->type && v->type->check_args) {
4772 struct value *val = var_value(&context, v);
4773 printf("func %.*s", v->name->name.len, v->name->name.txt);
4774 v->type->print_type_decl(v->type, stdout);
4776 print_exec(val->function, 0, brackets);
4778 print_value(v->type, val);
4779 printf("/* frame size %d */\n", v->type->function.local_size);
4785 ###### core functions
4787 static int analyse_funcs(struct parse_context *c)
4791 for (v = c->in_scope; v; v = v->in_scope) {
4794 if (v->depth != 0 || !v->type || !v->type->check_args)
4796 val = var_value(c, v);
4799 propagate_types(val->function, c, &ok, Tnone, 0);
4802 /* Make sure everything is still consistent */
4803 propagate_types(val->function, c, &ok, Tnone, 0);
4806 v->type->function.local_size = scope_finalize(c);
4811 static int analyse_main(struct type *type, struct parse_context *c)
4813 struct binode *bp = type->function.params;
4817 struct type *argv_type;
4818 struct text argv_type_name = { " argv", 5 };
4820 argv_type = add_type(c, argv_type_name, &array_prototype);
4821 argv_type->array.member = Tstr;
4822 argv_type->array.unspec = 1;
4824 for (b = bp; b; b = cast(binode, b->right)) {
4828 propagate_types(b->left, c, &ok, argv_type, 0);
4830 default: /* invalid */ // NOTEST
4831 propagate_types(b->left, c, &ok, Tnone, 0); // NOTEST
4837 return !c->parse_error;
4840 static void interp_main(struct parse_context *c, int argc, char **argv)
4842 struct value *progp = NULL;
4843 struct text main_name = { "main", 4 };
4844 struct variable *mainv;
4850 mainv = var_ref(c, main_name);
4852 progp = var_value(c, mainv);
4853 if (!progp || !progp->function) {
4854 fprintf(stderr, "oceani: no main function found.\n");
4858 if (!analyse_main(mainv->type, c)) {
4859 fprintf(stderr, "oceani: main has wrong type.\n");
4863 al = mainv->type->function.params;
4865 c->local_size = mainv->type->function.local_size;
4866 c->local = calloc(1, c->local_size);
4868 struct var *v = cast(var, al->left);
4869 struct value *vl = var_value(c, v->var);
4879 mpq_set_ui(argcq, argc, 1);
4880 memcpy(var_value(c, t->array.vsize), &argcq, sizeof(argcq));
4881 t->prepare_type(c, t, 0);
4882 array_init(v->var->type, vl);
4883 for (i = 0; i < argc; i++) {
4884 struct value *vl2 = vl->array + i * v->var->type->array.member->size;
4887 arg.str.txt = argv[i];
4888 arg.str.len = strlen(argv[i]);
4889 free_value(Tstr, vl2);
4890 dup_value(Tstr, &arg, vl2);
4894 al = cast(binode, al->right);
4896 v = interp_exec(c, progp->function, &vtype);
4897 free_value(vtype, &v);
4902 ###### ast functions
4903 void free_variable(struct variable *v)
4907 ## And now to test it out.
4909 Having a language requires having a "hello world" program. I'll
4910 provide a little more than that: a program that prints "Hello world"
4911 finds the GCD of two numbers, prints the first few elements of
4912 Fibonacci, performs a binary search for a number, and a few other
4913 things which will likely grow as the languages grows.
4915 ###### File: oceani.mk
4918 @echo "===== DEMO ====="
4919 ./oceani --section "demo: hello" oceani.mdc 55 33
4925 four ::= 2 + 2 ; five ::= 10/2
4926 const pie ::= "I like Pie";
4927 cake ::= "The cake is"
4935 func main(argv:[argc::]string)
4936 print "Hello World, what lovely oceans you have!"
4937 print "Are there", five, "?"
4938 print pi, pie, "but", cake
4940 A := $argv[1]; B := $argv[2]
4942 /* When a variable is defined in both branches of an 'if',
4943 * and used afterwards, the variables are merged.
4949 print "Is", A, "bigger than", B,"? ", bigger
4950 /* If a variable is not used after the 'if', no
4951 * merge happens, so types can be different
4954 double:string = "yes"
4955 print A, "is more than twice", B, "?", double
4958 print "double", B, "is", double
4963 if a > 0 and then b > 0:
4969 print "GCD of", A, "and", B,"is", a
4971 print a, "is not positive, cannot calculate GCD"
4973 print b, "is not positive, cannot calculate GCD"
4978 print "Fibonacci:", f1,f2,
4979 then togo = togo - 1
4987 /* Binary search... */
4992 mid := (lo + hi) / 2
5005 print "Yay, I found", target
5007 print "Closest I found was", lo
5012 // "middle square" PRNG. Not particularly good, but one my
5013 // Dad taught me - the first one I ever heard of.
5014 for i:=1; then i = i + 1; while i < size:
5015 n := list[i-1] * list[i-1]
5016 list[i] = (n / 100) % 10 000
5018 print "Before sort:",
5019 for i:=0; then i = i + 1; while i < size:
5023 for i := 1; then i=i+1; while i < size:
5024 for j:=i-1; then j=j-1; while j >= 0:
5025 if list[j] > list[j+1]:
5029 print " After sort:",
5030 for i:=0; then i = i + 1; while i < size:
5034 if 1 == 2 then print "yes"; else print "no"
5038 bob.alive = (bob.name == "Hello")
5039 print "bob", "is" if bob.alive else "isn't", "alive"