1 # Ocean Interpreter - Jamison Creek version
3 Ocean is intended to be a compiled language, so this interpreter is
4 not targeted at being the final product. It is, rather, an intermediate
5 stage and fills that role in two distinct ways.
7 Firstly, it exists as a platform to experiment with the early language
8 design. An interpreter is easy to write and easy to get working, so
9 the barrier for entry is lower if I aim to start with an interpreter.
11 Secondly, the plan for the Ocean compiler is to write it in the
12 [Ocean language](http://ocean-lang.org). To achieve this we naturally
13 need some sort of boot-strap process and this interpreter - written in
14 portable C - will fill that role. It will be used to bootstrap the
17 Two features that are not needed to fill either of these roles are
18 performance and completeness. The interpreter only needs to be fast
19 enough to run small test programs and occasionally to run the compiler
20 on itself. It only needs to be complete enough to test aspects of the
21 design which are developed before the compiler is working, and to run
22 the compiler on itself. Any features not used by the compiler when
23 compiling itself are superfluous. They may be included anyway, but
26 Nonetheless, the interpreter should end up being reasonably complete,
27 and any performance bottlenecks which appear and are easily fixed, will
32 This third version of the interpreter exists to test out some initial
33 ideas relating to types. Particularly it adds arrays (indexed from
34 zero) and simple structures. Basic control flow and variable scoping
35 are already fairly well established, as are basic numerical and
38 Some operators that have only recently been added, and so have not
39 generated all that much experience yet are "and then" and "or else" as
40 short-circuit Boolean operators, and the "if ... else" trinary
41 operator which can select between two expressions based on a third
42 (which appears syntactically in the middle).
44 The "func" clause currently only allows a "main" function to be
45 declared. That will be extended when proper function support is added.
47 An element that is present purely to make a usable language, and
48 without any expectation that they will remain, is the "print" statement
49 which performs simple output.
51 The current scalar types are "number", "Boolean", and "string".
52 Boolean will likely stay in its current form, the other two might, but
53 could just as easily be changed.
57 Versions of the interpreter which obviously do not support a complete
58 language will be named after creeks and streams. This one is Jamison
61 Once we have something reasonably resembling a complete language, the
62 names of rivers will be used.
63 Early versions of the compiler will be named after seas. Major
64 releases of the compiler will be named after oceans. Hopefully I will
65 be finished once I get to the Pacific Ocean release.
69 As well as parsing and executing a program, the interpreter can print
70 out the program from the parsed internal structure. This is useful
71 for validating the parsing.
72 So the main requirements of the interpreter are:
74 - Parse the program, possibly with tracing,
75 - Analyse the parsed program to ensure consistency,
77 - Execute the "main" function in the program, if no parsing or
78 consistency errors were found.
80 This is all performed by a single C program extracted with
83 There will be two formats for printing the program: a default and one
84 that uses bracketing. So a `--bracket` command line option is needed
85 for that. Normally the first code section found is used, however an
86 alternate section can be requested so that a file (such as this one)
87 can contain multiple programs. This is effected with the `--section`
90 This code must be compiled with `-fplan9-extensions` so that anonymous
91 structures can be used.
93 ###### File: oceani.mk
95 myCFLAGS := -Wall -g -fplan9-extensions
96 CFLAGS := $(filter-out $(myCFLAGS),$(CFLAGS)) $(myCFLAGS)
97 myLDLIBS:= libparser.o libscanner.o libmdcode.o -licuuc
98 LDLIBS := $(filter-out $(myLDLIBS),$(LDLIBS)) $(myLDLIBS)
100 all :: $(LDLIBS) oceani
101 oceani.c oceani.h : oceani.mdc parsergen
102 ./parsergen -o oceani --LALR --tag Parser oceani.mdc
103 oceani.mk: oceani.mdc md2c
106 oceani: oceani.o $(LDLIBS)
107 $(CC) $(CFLAGS) -o oceani oceani.o $(LDLIBS)
109 ###### Parser: header
111 struct parse_context;
113 struct parse_context {
114 struct token_config config;
122 #define container_of(ptr, type, member) ({ \
123 const typeof( ((type *)0)->member ) *__mptr = (ptr); \
124 (type *)( (char *)__mptr - offsetof(type,member) );})
126 #define config2context(_conf) container_of(_conf, struct parse_context, \
129 ###### Parser: reduce
130 struct parse_context *c = config2context(config);
138 #include <sys/mman.h>
157 static char Usage[] =
158 "Usage: oceani --trace --print --noexec --brackets --section=SectionName prog.ocn\n";
159 static const struct option long_options[] = {
160 {"trace", 0, NULL, 't'},
161 {"print", 0, NULL, 'p'},
162 {"noexec", 0, NULL, 'n'},
163 {"brackets", 0, NULL, 'b'},
164 {"section", 1, NULL, 's'},
167 const char *options = "tpnbs";
169 static void pr_err(char *msg) // NOTEST
171 fprintf(stderr, "%s\n", msg); // NOTEST
174 int main(int argc, char *argv[])
179 struct section *s = NULL, *ss;
180 char *section = NULL;
181 struct parse_context context = {
183 .ignored = (1 << TK_mark),
184 .number_chars = ".,_+- ",
189 int doprint=0, dotrace=0, doexec=1, brackets=0;
191 while ((opt = getopt_long(argc, argv, options, long_options, NULL))
194 case 't': dotrace=1; break;
195 case 'p': doprint=1; break;
196 case 'n': doexec=0; break;
197 case 'b': brackets=1; break;
198 case 's': section = optarg; break;
199 default: fprintf(stderr, Usage);
203 if (optind >= argc) {
204 fprintf(stderr, "oceani: no input file given\n");
207 fd = open(argv[optind], O_RDONLY);
209 fprintf(stderr, "oceani: cannot open %s\n", argv[optind]);
212 context.file_name = argv[optind];
213 len = lseek(fd, 0, 2);
214 file = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
215 s = code_extract(file, file+len, pr_err);
217 fprintf(stderr, "oceani: could not find any code in %s\n",
222 ## context initialization
225 for (ss = s; ss; ss = ss->next) {
226 struct text sec = ss->section;
227 if (sec.len == strlen(section) &&
228 strncmp(sec.txt, section, sec.len) == 0)
232 fprintf(stderr, "oceani: cannot find section %s\n",
239 fprintf(stderr, "oceani: no code found in requested section\n"); // NOTEST
240 goto cleanup; // NOTEST
243 parse_oceani(ss->code, &context.config, dotrace ? stderr : NULL);
245 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 // FIXME parser should pop scope even on error
265 while (context.scope_depth > 0)
268 ## free context types
269 ## free context storage
270 exit(context.parse_error ? 1 : 0);
275 The four requirements of parse, analyse, print, interpret apply to
276 each language element individually so that is how most of the code
279 Three of the four are fairly self explanatory. The one that requires
280 a little explanation is the analysis step.
282 The current language design does not require the types of variables to
283 be declared, but they must still have a single type. Different
284 operations impose different requirements on the variables, for example
285 addition requires both arguments to be numeric, and assignment
286 requires the variable on the left to have the same type as the
287 expression on the right.
289 Analysis involves propagating these type requirements around and
290 consequently setting the type of each variable. If any requirements
291 are violated (e.g. a string is compared with a number) or if a
292 variable needs to have two different types, then an error is raised
293 and the program will not run.
295 If the same variable is declared in both branchs of an 'if/else', or
296 in all cases of a 'switch' then the multiple instances may be merged
297 into just one variable if the variable is referenced after the
298 conditional statement. When this happens, the types must naturally be
299 consistent across all the branches. When the variable is not used
300 outside the if, the variables in the different branches are distinct
301 and can be of different types.
303 Undeclared names may only appear in "use" statements and "case" expressions.
304 These names are given a type of "label" and a unique value.
305 This allows them to fill the role of a name in an enumerated type, which
306 is useful for testing the `switch` statement.
308 As we will see, the condition part of a `while` statement can return
309 either a Boolean or some other type. This requires that the expected
310 type that gets passed around comprises a type and a flag to indicate
311 that `Tbool` is also permitted.
313 As there are, as yet, no distinct types that are compatible, there
314 isn't much subtlety in the analysis. When we have distinct number
315 types, this will become more interesting.
319 When analysis discovers an inconsistency it needs to report an error;
320 just refusing to run the code ensures that the error doesn't cascade,
321 but by itself it isn't very useful. A clear understanding of the sort
322 of error message that are useful will help guide the process of
325 At a simplistic level, the only sort of error that type analysis can
326 report is that the type of some construct doesn't match a contextual
327 requirement. For example, in `4 + "hello"` the addition provides a
328 contextual requirement for numbers, but `"hello"` is not a number. In
329 this particular example no further information is needed as the types
330 are obvious from local information. When a variable is involved that
331 isn't the case. It may be helpful to explain why the variable has a
332 particular type, by indicating the location where the type was set,
333 whether by declaration or usage.
335 Using a recursive-descent analysis we can easily detect a problem at
336 multiple locations. In "`hello:= "there"; 4 + hello`" the addition
337 will detect that one argument is not a number and the usage of `hello`
338 will detect that a number was wanted, but not provided. In this
339 (early) version of the language, we will generate error reports at
340 multiple locations, so the use of `hello` will report an error and
341 explain were the value was set, and the addition will report an error
342 and say why numbers are needed. To be able to report locations for
343 errors, each language element will need to record a file location
344 (line and column) and each variable will need to record the language
345 element where its type was set. For now we will assume that each line
346 of an error message indicates one location in the file, and up to 2
347 types. So we provide a `printf`-like function which takes a format, a
348 location (a `struct exec` which has not yet been introduced), and 2
349 types. "`%1`" reports the first type, "`%2`" reports the second. We
350 will need a function to print the location, once we know how that is
351 stored. e As will be explained later, there are sometimes extra rules for
352 type matching and they might affect error messages, we need to pass those
355 As well as type errors, we sometimes need to report problems with
356 tokens, which might be unexpected or might name a type that has not
357 been defined. For these we have `tok_err()` which reports an error
358 with a given token. Each of the error functions sets the flag in the
359 context so indicate that parsing failed.
363 static void fput_loc(struct exec *loc, FILE *f);
364 static void type_err(struct parse_context *c,
365 char *fmt, struct exec *loc,
366 struct type *t1, int rules, struct type *t2);
368 ###### core functions
370 static void type_err(struct parse_context *c,
371 char *fmt, struct exec *loc,
372 struct type *t1, int rules, struct type *t2)
374 fprintf(stderr, "%s:", c->file_name);
375 fput_loc(loc, stderr);
376 for (; *fmt ; fmt++) {
383 case '%': fputc(*fmt, stderr); break; // NOTEST
384 default: fputc('?', stderr); break; // NOTEST
386 type_print(t1, stderr);
389 type_print(t2, stderr);
398 static void tok_err(struct parse_context *c, char *fmt, struct token *t)
400 fprintf(stderr, "%s:%d:%d: %s: %.*s\n", c->file_name, t->line, t->col, fmt,
401 t->txt.len, t->txt.txt);
405 ## Entities: declared and predeclared.
407 There are various "things" that the language and/or the interpreter
408 needs to know about to parse and execute a program. These include
409 types, variables, values, and executable code. These are all lumped
410 together under the term "entities" (calling them "objects" would be
411 confusing) and introduced here. The following section will present the
412 different specific code elements which comprise or manipulate these
417 Values come in a wide range of types, with more likely to be added.
418 Each type needs to be able to print its own values (for convenience at
419 least) as well as to compare two values, at least for equality and
420 possibly for order. For now, values might need to be duplicated and
421 freed, though eventually such manipulations will be better integrated
424 Rather than requiring every numeric type to support all numeric
425 operations (add, multiple, etc), we allow types to be able to present
426 as one of a few standard types: integer, float, and fraction. The
427 existence of these conversion functions eventually enable types to
428 determine if they are compatible with other types, though such types
429 have not yet been implemented.
431 Named type are stored in a simple linked list. Objects of each type are
432 "values" which are often passed around by value.
439 ## value union fields
447 void (*init)(struct type *type, struct value *val);
448 void (*prepare_type)(struct parse_context *c, struct type *type, int parse_time);
449 void (*print)(struct type *type, struct value *val);
450 void (*print_type)(struct type *type, FILE *f);
451 int (*cmp_order)(struct type *t1, struct type *t2,
452 struct value *v1, struct value *v2);
453 int (*cmp_eq)(struct type *t1, struct type *t2,
454 struct value *v1, struct value *v2);
455 void (*dup)(struct type *type, struct value *vold, struct value *vnew);
456 void (*free)(struct type *type, struct value *val);
457 void (*free_type)(struct type *t);
458 long long (*to_int)(struct value *v);
459 double (*to_float)(struct value *v);
460 int (*to_mpq)(mpq_t *q, struct value *v);
469 struct type *typelist;
473 static struct type *find_type(struct parse_context *c, struct text s)
475 struct type *l = c->typelist;
478 text_cmp(l->name, s) != 0)
483 static struct type *add_type(struct parse_context *c, struct text s,
488 n = calloc(1, sizeof(*n));
491 n->next = c->typelist;
496 static void free_type(struct type *t)
498 /* The type is always a reference to something in the
499 * context, so we don't need to free anything.
503 static void free_value(struct type *type, struct value *v)
507 memset(v, 0x5a, type->size);
511 static void type_print(struct type *type, FILE *f)
514 fputs("*unknown*type*", f); // NOTEST
515 else if (type->name.len)
516 fprintf(f, "%.*s", type->name.len, type->name.txt);
517 else if (type->print_type)
518 type->print_type(type, f);
520 fputs("*invalid*type*", f); // NOTEST
523 static void val_init(struct type *type, struct value *val)
525 if (type && type->init)
526 type->init(type, val);
529 static void dup_value(struct type *type,
530 struct value *vold, struct value *vnew)
532 if (type && type->dup)
533 type->dup(type, vold, vnew);
536 static int value_cmp(struct type *tl, struct type *tr,
537 struct value *left, struct value *right)
539 if (tl && tl->cmp_order)
540 return tl->cmp_order(tl, tr, left, right);
541 if (tl && tl->cmp_eq) // NOTEST
542 return tl->cmp_eq(tl, tr, left, right); // NOTEST
546 static void print_value(struct type *type, struct value *v)
548 if (type && type->print)
549 type->print(type, v);
551 printf("*Unknown*"); // NOTEST
556 static void free_value(struct type *type, struct value *v);
557 static int type_compat(struct type *require, struct type *have, int rules);
558 static void type_print(struct type *type, FILE *f);
559 static void val_init(struct type *type, struct value *v);
560 static void dup_value(struct type *type,
561 struct value *vold, struct value *vnew);
562 static int value_cmp(struct type *tl, struct type *tr,
563 struct value *left, struct value *right);
564 static void print_value(struct type *type, struct value *v);
566 ###### free context types
568 while (context.typelist) {
569 struct type *t = context.typelist;
571 context.typelist = t->next;
577 Type can be specified for local variables, for fields in a structure,
578 for formal parameters to functions, and possibly elsewhere. Different
579 rules may apply in different contexts. As a minimum, a named type may
580 always be used. Currently the type of a formal parameter can be
581 different from types in other contexts, so we have a separate grammar
587 Type -> IDENTIFIER ${
588 $0 = find_type(c, $1.txt);
591 "error: undefined type", &$1);
598 FormalType -> Type ${ $0 = $<1; }$
599 ## formal type grammar
603 Values of the base types can be numbers, which we represent as
604 multi-precision fractions, strings, Booleans and labels. When
605 analysing the program we also need to allow for places where no value
606 is meaningful (type `Tnone`) and where we don't know what type to
607 expect yet (type is `NULL`).
609 Values are never shared, they are always copied when used, and freed
610 when no longer needed.
612 When propagating type information around the program, we need to
613 determine if two types are compatible, where type `NULL` is compatible
614 with anything. There are two special cases with type compatibility,
615 both related to the Conditional Statement which will be described
616 later. In some cases a Boolean can be accepted as well as some other
617 primary type, and in others any type is acceptable except a label (`Vlabel`).
618 A separate function encoding these cases will simplify some code later.
620 ###### type functions
622 int (*compat)(struct type *this, struct type *other);
626 static int type_compat(struct type *require, struct type *have, int rules)
628 if ((rules & Rboolok) && have == Tbool)
630 if ((rules & Rnolabel) && have == Tlabel)
632 if (!require || !have)
636 return require->compat(require, have);
638 return require == have;
643 #include "parse_string.h"
644 #include "parse_number.h"
647 myLDLIBS := libnumber.o libstring.o -lgmp
648 LDLIBS := $(filter-out $(myLDLIBS),$(LDLIBS)) $(myLDLIBS)
650 ###### type union fields
651 enum vtype {Vnone, Vstr, Vnum, Vbool, Vlabel} vtype;
653 ###### value union fields
660 static void _free_value(struct type *type, struct value *v)
664 switch (type->vtype) {
666 case Vstr: free(v->str.txt); break;
667 case Vnum: mpq_clear(v->num); break;
673 ###### value functions
675 static void _val_init(struct type *type, struct value *val)
677 switch(type->vtype) {
678 case Vnone: // NOTEST
681 mpq_init(val->num); break;
683 val->str.txt = malloc(1);
695 static void _dup_value(struct type *type,
696 struct value *vold, struct value *vnew)
698 switch (type->vtype) {
699 case Vnone: // NOTEST
702 vnew->label = vold->label;
705 vnew->bool = vold->bool;
709 mpq_set(vnew->num, vold->num);
712 vnew->str.len = vold->str.len;
713 vnew->str.txt = malloc(vnew->str.len);
714 memcpy(vnew->str.txt, vold->str.txt, vnew->str.len);
719 static int _value_cmp(struct type *tl, struct type *tr,
720 struct value *left, struct value *right)
724 return tl - tr; // NOTEST
726 case Vlabel: cmp = left->label == right->label ? 0 : 1; break;
727 case Vnum: cmp = mpq_cmp(left->num, right->num); break;
728 case Vstr: cmp = text_cmp(left->str, right->str); break;
729 case Vbool: cmp = left->bool - right->bool; break;
730 case Vnone: cmp = 0; // NOTEST
735 static void _print_value(struct type *type, struct value *v)
737 switch (type->vtype) {
738 case Vnone: // NOTEST
739 printf("*no-value*"); break; // NOTEST
740 case Vlabel: // NOTEST
741 printf("*label-%p*", v->label); break; // NOTEST
743 printf("%.*s", v->str.len, v->str.txt); break;
745 printf("%s", v->bool ? "True":"False"); break;
750 mpf_set_q(fl, v->num);
751 gmp_printf("%Fg", fl);
758 static void _free_value(struct type *type, struct value *v);
760 static struct type base_prototype = {
762 .print = _print_value,
763 .cmp_order = _value_cmp,
764 .cmp_eq = _value_cmp,
769 static struct type *Tbool, *Tstr, *Tnum, *Tnone, *Tlabel;
772 static struct type *add_base_type(struct parse_context *c, char *n,
773 enum vtype vt, int size)
775 struct text txt = { n, strlen(n) };
778 t = add_type(c, txt, &base_prototype);
781 t->align = size > sizeof(void*) ? sizeof(void*) : size;
782 if (t->size & (t->align - 1))
783 t->size = (t->size | (t->align - 1)) + 1; // NOTEST
787 ###### context initialization
789 Tbool = add_base_type(&context, "Boolean", Vbool, sizeof(char));
790 Tstr = add_base_type(&context, "string", Vstr, sizeof(struct text));
791 Tnum = add_base_type(&context, "number", Vnum, sizeof(mpq_t));
792 Tnone = add_base_type(&context, "none", Vnone, 0);
793 Tlabel = add_base_type(&context, "label", Vlabel, sizeof(void*));
797 Variables are scoped named values. We store the names in a linked list
798 of "bindings" sorted in lexical order, and use sequential search and
805 struct binding *next; // in lexical order
809 This linked list is stored in the parse context so that "reduce"
810 functions can find or add variables, and so the analysis phase can
811 ensure that every variable gets a type.
815 struct binding *varlist; // In lexical order
819 static struct binding *find_binding(struct parse_context *c, struct text s)
821 struct binding **l = &c->varlist;
826 (cmp = text_cmp((*l)->name, s)) < 0)
830 n = calloc(1, sizeof(*n));
837 Each name can be linked to multiple variables defined in different
838 scopes. Each scope starts where the name is declared and continues
839 until the end of the containing code block. Scopes of a given name
840 cannot nest, so a declaration while a name is in-scope is an error.
842 ###### binding fields
843 struct variable *var;
847 struct variable *previous;
849 struct binding *name;
850 struct exec *where_decl;// where name was declared
851 struct exec *where_set; // where type was set
855 When a scope closes, the values of the variables might need to be freed.
856 This happens in the context of some `struct exec` and each `exec` will
857 need to know which variables need to be freed when it completes.
860 struct variable *to_free;
862 ####### variable fields
863 struct exec *cleanup_exec;
864 struct variable *next_free;
866 ####### interp exec cleanup
869 for (v = e->to_free; v; v = v->next_free) {
870 struct value *val = var_value(c, v);
871 free_value(v->type, val);
876 static void variable_unlink_exec(struct variable *v)
878 struct variable **vp;
879 if (!v->cleanup_exec)
881 for (vp = &v->cleanup_exec->to_free;
882 *vp; vp = &(*vp)->next_free) {
886 v->cleanup_exec = NULL;
891 While the naming seems strange, we include local constants in the
892 definition of variables. A name declared `var := value` can
893 subsequently be changed, but a name declared `var ::= value` cannot -
896 ###### variable fields
899 Scopes in parallel branches can be partially merged. More
900 specifically, if a given name is declared in both branches of an
901 if/else then its scope is a candidate for merging. Similarly if
902 every branch of an exhaustive switch (e.g. has an "else" clause)
903 declares a given name, then the scopes from the branches are
904 candidates for merging.
906 Note that names declared inside a loop (which is only parallel to
907 itself) are never visible after the loop. Similarly names defined in
908 scopes which are not parallel, such as those started by `for` and
909 `switch`, are never visible after the scope. Only variables defined in
910 both `then` and `else` (including the implicit then after an `if`, and
911 excluding `then` used with `for`) and in all `case`s and `else` of a
912 `switch` or `while` can be visible beyond the `if`/`switch`/`while`.
914 Labels, which are a bit like variables, follow different rules.
915 Labels are not explicitly declared, but if an undeclared name appears
916 in a context where a label is legal, that effectively declares the
917 name as a label. The declaration remains in force (or in scope) at
918 least to the end of the immediately containing block and conditionally
919 in any larger containing block which does not declare the name in some
920 other way. Importantly, the conditional scope extension happens even
921 if the label is only used in one parallel branch of a conditional --
922 when used in one branch it is treated as having been declared in all
925 Merge candidates are tentatively visible beyond the end of the
926 branching statement which creates them. If the name is used, the
927 merge is affirmed and they become a single variable visible at the
928 outer layer. If not - if it is redeclared first - the merge lapses.
930 To track scopes we have an extra stack, implemented as a linked list,
931 which roughly parallels the parse stack and which is used exclusively
932 for scoping. When a new scope is opened, a new frame is pushed and
933 the child-count of the parent frame is incremented. This child-count
934 is used to distinguish between the first of a set of parallel scopes,
935 in which declared variables must not be in scope, and subsequent
936 branches, whether they may already be conditionally scoped.
938 To push a new frame *before* any code in the frame is parsed, we need a
939 grammar reduction. This is most easily achieved with a grammar
940 element which derives the empty string, and creates the new scope when
941 it is recognised. This can be placed, for example, between a keyword
942 like "if" and the code following it.
946 struct scope *parent;
952 struct scope *scope_stack;
955 static void scope_pop(struct parse_context *c)
957 struct scope *s = c->scope_stack;
959 c->scope_stack = s->parent;
964 static void scope_push(struct parse_context *c)
966 struct scope *s = calloc(1, sizeof(*s));
968 c->scope_stack->child_count += 1;
969 s->parent = c->scope_stack;
977 OpenScope -> ${ scope_push(c); }$
979 Each variable records a scope depth and is in one of four states:
981 - "in scope". This is the case between the declaration of the
982 variable and the end of the containing block, and also between
983 the usage with affirms a merge and the end of that block.
985 The scope depth is not greater than the current parse context scope
986 nest depth. When the block of that depth closes, the state will
987 change. To achieve this, all "in scope" variables are linked
988 together as a stack in nesting order.
990 - "pending". The "in scope" block has closed, but other parallel
991 scopes are still being processed. So far, every parallel block at
992 the same level that has closed has declared the name.
994 The scope depth is the depth of the last parallel block that
995 enclosed the declaration, and that has closed.
997 - "conditionally in scope". The "in scope" block and all parallel
998 scopes have closed, and no further mention of the name has been seen.
999 This state includes a secondary nest depth (`min_depth`) which records
1000 the outermost scope seen since the variable became conditionally in
1001 scope. If a use of the name is found, the variable becomes "in scope"
1002 and that secondary depth becomes the recorded scope depth. If the
1003 name is declared as a new variable, the old variable becomes "out of
1004 scope" and the recorded scope depth stays unchanged.
1006 - "out of scope". The variable is neither in scope nor conditionally
1007 in scope. It is permanently out of scope now and can be removed from
1008 the "in scope" stack.
1010 ###### variable fields
1011 int depth, min_depth;
1012 enum { OutScope, PendingScope, CondScope, InScope } scope;
1013 struct variable *in_scope;
1015 ###### parse context
1017 struct variable *in_scope;
1019 All variables with the same name are linked together using the
1020 'previous' link. Those variable that have been affirmatively merged all
1021 have a 'merged' pointer that points to one primary variable - the most
1022 recently declared instance. When merging variables, we need to also
1023 adjust the 'merged' pointer on any other variables that had previously
1024 been merged with the one that will no longer be primary.
1026 A variable that is no longer the most recent instance of a name may
1027 still have "pending" scope, if it might still be merged with most
1028 recent instance. These variables don't really belong in the
1029 "in_scope" list, but are not immediately removed when a new instance
1030 is found. Instead, they are detected and ignored when considering the
1031 list of in_scope names.
1033 The storage of the value of a variable will be described later. For now
1034 we just need to know that when a variable goes out of scope, it might
1035 need to be freed. For this we need to be able to find it, so assume that
1036 `var_value()` will provide that.
1038 ###### variable fields
1039 struct variable *merged;
1041 ###### ast functions
1043 static void variable_merge(struct variable *primary, struct variable *secondary)
1047 primary = primary->merged;
1049 for (v = primary->previous; v; v=v->previous)
1050 if (v == secondary || v == secondary->merged ||
1051 v->merged == secondary ||
1052 v->merged == secondary->merged) {
1053 v->scope = OutScope;
1054 v->merged = primary;
1055 variable_unlink_exec(v);
1059 ###### forward decls
1060 static struct value *var_value(struct parse_context *c, struct variable *v);
1062 ###### free global vars
1064 while (context.varlist) {
1065 struct binding *b = context.varlist;
1066 struct variable *v = b->var;
1067 context.varlist = b->next;
1070 struct variable *next = v->previous;
1073 free_value(v->type, var_value(&context, v));
1075 // This is a global constant
1076 free_exec(v->where_decl);
1083 #### Manipulating Bindings
1085 When a name is conditionally visible, a new declaration discards the
1086 old binding - the condition lapses. Conversely a usage of the name
1087 affirms the visibility and extends it to the end of the containing
1088 block - i.e. the block that contains both the original declaration and
1089 the latest usage. This is determined from `min_depth`. When a
1090 conditionally visible variable gets affirmed like this, it is also
1091 merged with other conditionally visible variables with the same name.
1093 When we parse a variable declaration we either report an error if the
1094 name is currently bound, or create a new variable at the current nest
1095 depth if the name is unbound or bound to a conditionally scoped or
1096 pending-scope variable. If the previous variable was conditionally
1097 scoped, it and its homonyms becomes out-of-scope.
1099 When we parse a variable reference (including non-declarative assignment
1100 "foo = bar") we report an error if the name is not bound or is bound to
1101 a pending-scope variable; update the scope if the name is bound to a
1102 conditionally scoped variable; or just proceed normally if the named
1103 variable is in scope.
1105 When we exit a scope, any variables bound at this level are either
1106 marked out of scope or pending-scoped, depending on whether the scope
1107 was sequential or parallel. Here a "parallel" scope means the "then"
1108 or "else" part of a conditional, or any "case" or "else" branch of a
1109 switch. Other scopes are "sequential".
1111 When exiting a parallel scope we check if there are any variables that
1112 were previously pending and are still visible. If there are, then
1113 they weren't redeclared in the most recent scope, so they cannot be
1114 merged and must become out-of-scope. If it is not the first of
1115 parallel scopes (based on `child_count`), we check that there was a
1116 previous binding that is still pending-scope. If there isn't, the new
1117 variable must now be out-of-scope.
1119 When exiting a sequential scope that immediately enclosed parallel
1120 scopes, we need to resolve any pending-scope variables. If there was
1121 no `else` clause, and we cannot determine that the `switch` was exhaustive,
1122 we need to mark all pending-scope variable as out-of-scope. Otherwise
1123 all pending-scope variables become conditionally scoped.
1126 enum closetype { CloseSequential, CloseParallel, CloseElse };
1128 ###### ast functions
1130 static struct variable *var_decl(struct parse_context *c, struct text s)
1132 struct binding *b = find_binding(c, s);
1133 struct variable *v = b->var;
1135 switch (v ? v->scope : OutScope) {
1137 /* Caller will report the error */
1141 v && v->scope == CondScope;
1143 v->scope = OutScope;
1147 v = calloc(1, sizeof(*v));
1148 v->previous = b->var;
1152 v->min_depth = v->depth = c->scope_depth;
1154 v->in_scope = c->in_scope;
1160 static struct variable *var_ref(struct parse_context *c, struct text s)
1162 struct binding *b = find_binding(c, s);
1163 struct variable *v = b->var;
1164 struct variable *v2;
1166 switch (v ? v->scope : OutScope) {
1169 /* Caller will report the error */
1172 /* All CondScope variables of this name need to be merged
1173 * and become InScope
1175 v->depth = v->min_depth;
1177 for (v2 = v->previous;
1178 v2 && v2->scope == CondScope;
1180 variable_merge(v, v2);
1188 static void var_block_close(struct parse_context *c, enum closetype ct,
1191 /* Close off all variables that are in_scope.
1192 * Some variables in c->scope may already be not-in-scope,
1193 * such as when a PendingScope variable is hidden by a new
1194 * variable with the same name.
1195 * So we check for v->name->var != v and drop them.
1196 * If we choose to make a variable OutScope, we drop it
1199 struct variable *v, **vp, *v2;
1202 for (vp = &c->in_scope;
1203 (v = *vp) && v->min_depth > c->scope_depth;
1204 (v->scope == OutScope || v->name->var != v)
1205 ? (*vp = v->in_scope, 0)
1206 : ( vp = &v->in_scope, 0)) {
1207 v->min_depth = c->scope_depth;
1208 if (v->name->var != v)
1209 /* This is still in scope, but we haven't just
1213 v->min_depth = c->scope_depth;
1214 if (v->scope == InScope && e) {
1215 /* This variable gets cleaned up when 'e' finishes */
1216 variable_unlink_exec(v);
1217 v->cleanup_exec = e;
1218 v->next_free = e->to_free;
1223 case CloseParallel: /* handle PendingScope */
1227 if (c->scope_stack->child_count == 1)
1228 /* first among parallel branches */
1229 v->scope = PendingScope;
1230 else if (v->previous &&
1231 v->previous->scope == PendingScope)
1232 /* all previous branches used name */
1233 v->scope = PendingScope;
1234 else if (v->type == Tlabel)
1235 /* Labels remain pending even when not used */
1236 v->scope = PendingScope; // UNTESTED
1238 v->scope = OutScope;
1239 if (ct == CloseElse) {
1240 /* All Pending variables with this name
1241 * are now Conditional */
1243 v2 && v2->scope == PendingScope;
1245 v2->scope = CondScope;
1249 /* Not possible as it would require
1250 * parallel scope to be nested immediately
1251 * in a parallel scope, and that never
1255 /* Not possible as we already tested for
1261 case CloseSequential:
1262 if (v->type == Tlabel)
1263 v->scope = PendingScope;
1266 v->scope = OutScope;
1269 /* There was no 'else', so we can only become
1270 * conditional if we know the cases were exhaustive,
1271 * and that doesn't mean anything yet.
1272 * So only labels become conditional..
1275 v2 && v2->scope == PendingScope;
1277 if (v2->type == Tlabel)
1278 v2->scope = CondScope;
1280 v2->scope = OutScope;
1283 case OutScope: break;
1292 The value of a variable is store separately from the variable, on an
1293 analogue of a stack frame. There are (currently) two frames that can be
1294 active. A global frame which currently only stores constants, and a
1295 stacked frame which stores local variables. Each variable knows if it
1296 is global or not, and what its index into the frame is.
1298 Values in the global frame are known immediately they are relevant, so
1299 the frame needs to be reallocated as it grows so it can store those
1300 values. The local frame doesn't get values until the interpreted phase
1301 is started, so there is no need to allocate until the size is known.
1303 We initialize the `frame_pos` to an impossible value, so that we can
1304 tell if it was set or not later.
1306 ###### variable fields
1310 ###### variable init
1313 ###### parse context
1315 short global_size, global_alloc;
1317 void *global, *local;
1319 ###### ast functions
1321 static struct value *var_value(struct parse_context *c, struct variable *v)
1324 if (!c->local || !v->type)
1325 return NULL; // NOTEST
1326 if (v->frame_pos + v->type->size > c->local_size) {
1327 printf("INVALID frame_pos\n"); // NOTEST
1330 return c->local + v->frame_pos;
1332 if (c->global_size > c->global_alloc) {
1333 int old = c->global_alloc;
1334 c->global_alloc = (c->global_size | 1023) + 1024;
1335 c->global = realloc(c->global, c->global_alloc);
1336 memset(c->global + old, 0, c->global_alloc - old);
1338 return c->global + v->frame_pos;
1341 static struct value *global_alloc(struct parse_context *c, struct type *t,
1342 struct variable *v, struct value *init)
1345 struct variable scratch;
1347 if (t->prepare_type)
1348 t->prepare_type(c, t, 1); // NOTEST
1350 if (c->global_size & (t->align - 1))
1351 c->global_size = (c->global_size + t->align) & ~(t->align-1);
1356 v->frame_pos = c->global_size;
1358 c->global_size += v->type->size;
1359 ret = var_value(c, v);
1361 memcpy(ret, init, t->size);
1367 As global values are found -- struct field initializers, labels etc --
1368 `global_alloc()` is called to record the value in the global frame.
1370 When the program is fully parsed, we need to walk the list of variables
1371 to find any that weren't merged away and that aren't global, and to
1372 calculate the frame size and assign a frame position for each
1373 variable. For this we have `scope_finalize()`.
1375 ###### ast functions
1377 static int scope_finalize(struct parse_context *c)
1382 for (b = c->varlist; b; b = b->next) {
1384 for (v = b->var; v; v = v->previous) {
1385 struct type *t = v->type;
1392 if (size & (t->align - 1))
1393 size = (size + t->align) & ~(t->align-1);
1394 v->frame_pos = size;
1395 size += v->type->size;
1401 ###### free context storage
1402 free(context.global);
1406 Executables can be lots of different things. In many cases an
1407 executable is just an operation combined with one or two other
1408 executables. This allows for expressions and lists etc. Other times an
1409 executable is something quite specific like a constant or variable name.
1410 So we define a `struct exec` to be a general executable with a type, and
1411 a `struct binode` which is a subclass of `exec`, forms a node in a
1412 binary tree, and holds an operation. There will be other subclasses,
1413 and to access these we need to be able to `cast` the `exec` into the
1414 various other types. The first field in any `struct exec` is the type
1415 from the `exec_types` enum.
1418 #define cast(structname, pointer) ({ \
1419 const typeof( ((struct structname *)0)->type) *__mptr = &(pointer)->type; \
1420 if (__mptr && *__mptr != X##structname) abort(); \
1421 (struct structname *)( (char *)__mptr);})
1423 #define new(structname) ({ \
1424 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1425 __ptr->type = X##structname; \
1426 __ptr->line = -1; __ptr->column = -1; \
1429 #define new_pos(structname, token) ({ \
1430 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1431 __ptr->type = X##structname; \
1432 __ptr->line = token.line; __ptr->column = token.col; \
1441 enum exec_types type;
1450 struct exec *left, *right;
1453 ###### ast functions
1455 static int __fput_loc(struct exec *loc, FILE *f)
1459 if (loc->line >= 0) {
1460 fprintf(f, "%d:%d: ", loc->line, loc->column);
1463 if (loc->type == Xbinode)
1464 return __fput_loc(cast(binode,loc)->left, f) ||
1465 __fput_loc(cast(binode,loc)->right, f); // NOTEST
1468 static void fput_loc(struct exec *loc, FILE *f)
1470 if (!__fput_loc(loc, f))
1471 fprintf(f, "??:??: ");
1474 Each different type of `exec` node needs a number of functions defined,
1475 a bit like methods. We must be able to free it, print it, analyse it
1476 and execute it. Once we have specific `exec` types we will need to
1477 parse them too. Let's take this a bit more slowly.
1481 The parser generator requires a `free_foo` function for each struct
1482 that stores attributes and they will often be `exec`s and subtypes
1483 there-of. So we need `free_exec` which can handle all the subtypes,
1484 and we need `free_binode`.
1486 ###### ast functions
1488 static void free_binode(struct binode *b)
1493 free_exec(b->right);
1497 ###### core functions
1498 static void free_exec(struct exec *e)
1507 ###### forward decls
1509 static void free_exec(struct exec *e);
1511 ###### free exec cases
1512 case Xbinode: free_binode(cast(binode, e)); break;
1516 Printing an `exec` requires that we know the current indent level for
1517 printing line-oriented components. As will become clear later, we
1518 also want to know what sort of bracketing to use.
1520 ###### ast functions
1522 static void do_indent(int i, char *str)
1529 ###### core functions
1530 static void print_binode(struct binode *b, int indent, int bracket)
1534 ## print binode cases
1538 static void print_exec(struct exec *e, int indent, int bracket)
1544 print_binode(cast(binode, e), indent, bracket); break;
1549 do_indent(indent, "/* FREE");
1550 for (v = e->to_free; v; v = v->next_free) {
1551 printf(" %.*s", v->name->name.len, v->name->name.txt);
1552 if (v->frame_pos >= 0)
1553 printf("(%d+%d)", v->frame_pos,
1554 v->type ? v->type->size:0);
1560 ###### forward decls
1562 static void print_exec(struct exec *e, int indent, int bracket);
1566 As discussed, analysis involves propagating type requirements around the
1567 program and looking for errors.
1569 So `propagate_types` is passed an expected type (being a `struct type`
1570 pointer together with some `val_rules` flags) that the `exec` is
1571 expected to return, and returns the type that it does return, either
1572 of which can be `NULL` signifying "unknown". An `ok` flag is passed
1573 by reference. It is set to `0` when an error is found, and `2` when
1574 any change is made. If it remains unchanged at `1`, then no more
1575 propagation is needed.
1579 enum val_rules {Rnolabel = 1<<0, Rboolok = 1<<1, Rnoconstant = 1<<2};
1583 if (rules & Rnolabel)
1584 fputs(" (labels not permitted)", stderr);
1587 ###### forward decls
1588 static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1589 struct type *type, int rules);
1590 ###### core functions
1592 static struct type *__propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1593 struct type *type, int rules)
1600 switch (prog->type) {
1603 struct binode *b = cast(binode, prog);
1605 ## propagate binode cases
1609 ## propagate exec cases
1614 static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1615 struct type *type, int rules)
1617 struct type *ret = __propagate_types(prog, c, ok, type, rules);
1626 Interpreting an `exec` doesn't require anything but the `exec`. State
1627 is stored in variables and each variable will be directly linked from
1628 within the `exec` tree. The exception to this is the `main` function
1629 which needs to look at command line arguments. This function will be
1630 interpreted separately.
1632 Each `exec` can return a value combined with a type in `struct lrval`.
1633 The type may be `Tnone` but must be non-NULL. Some `exec`s will return
1634 the location of a value, which can be updated, in `lval`. Others will
1635 set `lval` to NULL indicating that there is a value of appropriate type
1638 ###### core functions
1642 struct value rval, *lval;
1645 /* If dest is passed, dtype must give the expected type, and
1646 * result can go there, in which case type is returned as NULL.
1648 static struct lrval _interp_exec(struct parse_context *c, struct exec *e,
1649 struct value *dest, struct type *dtype);
1651 static struct value interp_exec(struct parse_context *c, struct exec *e,
1652 struct type **typeret)
1654 struct lrval ret = _interp_exec(c, e, NULL, NULL);
1656 if (!ret.type) abort();
1658 *typeret = ret.type;
1660 dup_value(ret.type, ret.lval, &ret.rval);
1664 static struct value *linterp_exec(struct parse_context *c, struct exec *e,
1665 struct type **typeret)
1667 struct lrval ret = _interp_exec(c, e, NULL, NULL);
1669 if (!ret.type) abort();
1671 *typeret = ret.type;
1673 free_value(ret.type, &ret.rval);
1677 /* dinterp_exec is used when the destination type is certain and
1678 * the value has a place to go.
1680 static void dinterp_exec(struct parse_context *c, struct exec *e,
1681 struct value *dest, struct type *dtype,
1684 struct lrval ret = _interp_exec(c, e, dest, dtype);
1688 free_value(dtype, dest);
1690 dup_value(dtype, ret.lval, dest);
1692 memcpy(dest, &ret.rval, dtype->size);
1695 static struct lrval _interp_exec(struct parse_context *c, struct exec *e,
1696 struct value *dest, struct type *dtype)
1698 /* If the result is copied to dest, ret.type is set to NULL */
1700 struct value rv = {}, *lrv = NULL;
1701 struct type *rvtype;
1703 rvtype = ret.type = Tnone;
1713 struct binode *b = cast(binode, e);
1714 struct value left, right, *lleft;
1715 struct type *ltype, *rtype;
1716 ltype = rtype = Tnone;
1718 ## interp binode cases
1720 free_value(ltype, &left);
1721 free_value(rtype, &right);
1724 ## interp exec cases
1731 ## interp exec cleanup
1737 Now that we have the shape of the interpreter in place we can add some
1738 complex types and connected them in to the data structures and the
1739 different phases of parse, analyse, print, interpret.
1741 Thus far we have arrays and structs.
1745 Arrays can be declared by giving a size and a type, as `[size]type' so
1746 `freq:[26]number` declares `freq` to be an array of 26 numbers. The
1747 size can be either a literal number, or a named constant. Some day an
1748 arbitrary expression will be supported.
1750 As a formal parameter to a function, the array can be declared with a
1751 new variable as the size: `name:[size::number]string`. The `size`
1752 variable is set to the size of the array and must be a constant. As
1753 `number` is the only supported type, it can be left out:
1754 `name:[size::]string`.
1756 Arrays cannot be assigned. When pointers are introduced we will also
1757 introduce array slices which can refer to part or all of an array -
1758 the assignment syntax will create a slice. For now, an array can only
1759 ever be referenced by the name it is declared with. It is likely that
1760 a "`copy`" primitive will eventually be define which can be used to
1761 make a copy of an array with controllable recursive depth.
1763 For now we have two sorts of array, those with fixed size either because
1764 it is given as a literal number or because it is a struct member (which
1765 cannot have a runtime-changing size), and those with a size that is
1766 determined at runtime - local variables with a const size. The former
1767 have their size calculated at parse time, the latter at run time.
1769 For the latter type, the `size` field of the type is the size of a
1770 pointer, and the array is reallocated every time it comes into scope.
1772 We differentiate struct fields with a const size from local variables
1773 with a const size by whether they are prepared at parse time or not.
1775 ###### type union fields
1778 int unspec; // size is unspecified - vsize must be set.
1781 struct variable *vsize;
1782 struct type *member;
1785 ###### value union fields
1786 void *array; // used if not static_size
1788 ###### value functions
1790 static void array_prepare_type(struct parse_context *c, struct type *type,
1793 struct value *vsize;
1795 if (!type->array.vsize || type->array.static_size)
1798 vsize = var_value(c, type->array.vsize);
1800 mpz_tdiv_q(q, mpq_numref(vsize->num), mpq_denref(vsize->num));
1801 type->array.size = mpz_get_si(q);
1805 type->array.static_size = 1;
1806 type->size = type->array.size * type->array.member->size;
1807 type->align = type->array.member->align;
1811 static void array_init(struct type *type, struct value *val)
1814 void *ptr = val->ptr;
1818 if (!type->array.static_size) {
1819 val->array = calloc(type->array.size,
1820 type->array.member->size);
1823 for (i = 0; i < type->array.size; i++) {
1825 v = (void*)ptr + i * type->array.member->size;
1826 val_init(type->array.member, v);
1830 static void array_free(struct type *type, struct value *val)
1833 void *ptr = val->ptr;
1835 if (!type->array.static_size)
1837 for (i = 0; i < type->array.size; i++) {
1839 v = (void*)ptr + i * type->array.member->size;
1840 free_value(type->array.member, v);
1842 if (!type->array.static_size)
1846 static int array_compat(struct type *require, struct type *have)
1848 if (have->compat != require->compat)
1850 /* Both are arrays, so we can look at details */
1851 if (!type_compat(require->array.member, have->array.member, 0))
1853 if (have->array.unspec && require->array.unspec) {
1854 if (have->array.vsize && require->array.vsize &&
1855 have->array.vsize != require->array.vsize) // UNTESTED
1856 /* sizes might not be the same */
1857 return 0; // UNTESTED
1860 if (have->array.unspec || require->array.unspec)
1861 return 1; // UNTESTED
1862 if (require->array.vsize == NULL && have->array.vsize == NULL)
1863 return require->array.size == have->array.size;
1865 return require->array.vsize == have->array.vsize; // UNTESTED
1868 static void array_print_type(struct type *type, FILE *f)
1871 if (type->array.vsize) {
1872 struct binding *b = type->array.vsize->name;
1873 fprintf(f, "%.*s%s]", b->name.len, b->name.txt,
1874 type->array.unspec ? "::" : "");
1876 fprintf(f, "%d]", type->array.size);
1877 type_print(type->array.member, f);
1880 static struct type array_prototype = {
1882 .prepare_type = array_prepare_type,
1883 .print_type = array_print_type,
1884 .compat = array_compat,
1886 .size = sizeof(void*),
1887 .align = sizeof(void*),
1890 ###### declare terminals
1895 | [ NUMBER ] Type ${ {
1898 struct text noname = { "", 0 };
1901 $0 = t = add_type(c, noname, &array_prototype);
1902 t->array.member = $<4;
1903 t->array.vsize = NULL;
1904 if (number_parse(num, tail, $2.txt) == 0)
1905 tok_err(c, "error: unrecognised number", &$2);
1907 tok_err(c, "error: unsupported number suffix", &$2);
1910 t->array.size = mpz_get_ui(mpq_numref(num));
1911 if (mpz_cmp_ui(mpq_denref(num), 1) != 0) {
1912 tok_err(c, "error: array size must be an integer",
1914 } else if (mpz_cmp_ui(mpq_numref(num), 1UL << 30) >= 0)
1915 tok_err(c, "error: array size is too large",
1919 t->array.static_size = 1;
1920 t->size = t->array.size * t->array.member->size;
1921 t->align = t->array.member->align;
1924 | [ IDENTIFIER ] Type ${ {
1925 struct variable *v = var_ref(c, $2.txt);
1926 struct text noname = { "", 0 };
1929 tok_err(c, "error: name undeclared", &$2);
1930 else if (!v->constant)
1931 tok_err(c, "error: array size must be a constant", &$2);
1933 $0 = add_type(c, noname, &array_prototype);
1934 $0->array.member = $<4;
1936 $0->array.vsize = v;
1941 OptType -> Type ${ $0 = $<1; }$
1944 ###### formal type grammar
1946 | [ IDENTIFIER :: OptType ] Type ${ {
1947 struct variable *v = var_decl(c, $ID.txt);
1948 struct text noname = { "", 0 };
1954 $0 = add_type(c, noname, &array_prototype);
1955 $0->array.member = $<6;
1957 $0->array.unspec = 1;
1958 $0->array.vsize = v;
1964 ###### variable grammar
1966 | Variable [ Expression ] ${ {
1967 struct binode *b = new(binode);
1974 ###### print binode cases
1976 print_exec(b->left, -1, bracket);
1978 print_exec(b->right, -1, bracket);
1982 ###### propagate binode cases
1984 /* left must be an array, right must be a number,
1985 * result is the member type of the array
1987 propagate_types(b->right, c, ok, Tnum, 0);
1988 t = propagate_types(b->left, c, ok, NULL, rules & Rnoconstant);
1989 if (!t || t->compat != array_compat) {
1990 type_err(c, "error: %1 cannot be indexed", prog, t, 0, NULL);
1993 if (!type_compat(type, t->array.member, rules)) {
1994 type_err(c, "error: have %1 but need %2", prog,
1995 t->array.member, rules, type);
1997 return t->array.member;
2001 ###### interp binode cases
2007 lleft = linterp_exec(c, b->left, <ype);
2008 right = interp_exec(c, b->right, &rtype);
2010 mpz_tdiv_q(q, mpq_numref(right.num), mpq_denref(right.num));
2014 if (ltype->array.static_size)
2017 ptr = *(void**)lleft;
2018 rvtype = ltype->array.member;
2019 if (i >= 0 && i < ltype->array.size)
2020 lrv = ptr + i * rvtype->size;
2022 val_init(ltype->array.member, &rv); // UNSAFE
2029 A `struct` is a data-type that contains one or more other data-types.
2030 It differs from an array in that each member can be of a different
2031 type, and they are accessed by name rather than by number. Thus you
2032 cannot choose an element by calculation, you need to know what you
2035 The language makes no promises about how a given structure will be
2036 stored in memory - it is free to rearrange fields to suit whatever
2037 criteria seems important.
2039 Structs are declared separately from program code - they cannot be
2040 declared in-line in a variable declaration like arrays can. A struct
2041 is given a name and this name is used to identify the type - the name
2042 is not prefixed by the word `struct` as it would be in C.
2044 Structs are only treated as the same if they have the same name.
2045 Simply having the same fields in the same order is not enough. This
2046 might change once we can create structure initializers from a list of
2049 Each component datum is identified much like a variable is declared,
2050 with a name, one or two colons, and a type. The type cannot be omitted
2051 as there is no opportunity to deduce the type from usage. An initial
2052 value can be given following an equals sign, so
2054 ##### Example: a struct type
2060 would declare a type called "complex" which has two number fields,
2061 each initialised to zero.
2063 Struct will need to be declared separately from the code that uses
2064 them, so we will need to be able to print out the declaration of a
2065 struct when reprinting the whole program. So a `print_type_decl` type
2066 function will be needed.
2068 ###### type union fields
2080 ###### type functions
2081 void (*print_type_decl)(struct type *type, FILE *f);
2083 ###### value functions
2085 static void structure_init(struct type *type, struct value *val)
2089 for (i = 0; i < type->structure.nfields; i++) {
2091 v = (void*) val->ptr + type->structure.fields[i].offset;
2092 if (type->structure.fields[i].init)
2093 dup_value(type->structure.fields[i].type,
2094 type->structure.fields[i].init,
2097 val_init(type->structure.fields[i].type, v);
2101 static void structure_free(struct type *type, struct value *val)
2105 for (i = 0; i < type->structure.nfields; i++) {
2107 v = (void*)val->ptr + type->structure.fields[i].offset;
2108 free_value(type->structure.fields[i].type, v);
2112 static void structure_free_type(struct type *t)
2115 for (i = 0; i < t->structure.nfields; i++)
2116 if (t->structure.fields[i].init) {
2117 free_value(t->structure.fields[i].type,
2118 t->structure.fields[i].init);
2120 free(t->structure.fields);
2123 static struct type structure_prototype = {
2124 .init = structure_init,
2125 .free = structure_free,
2126 .free_type = structure_free_type,
2127 .print_type_decl = structure_print_type,
2141 ###### free exec cases
2143 free_exec(cast(fieldref, e)->left);
2147 ###### declare terminals
2150 ###### variable grammar
2152 | Variable . IDENTIFIER ${ {
2153 struct fieldref *fr = new_pos(fieldref, $2);
2160 ###### print exec cases
2164 struct fieldref *f = cast(fieldref, e);
2165 print_exec(f->left, -1, bracket);
2166 printf(".%.*s", f->name.len, f->name.txt);
2170 ###### ast functions
2171 static int find_struct_index(struct type *type, struct text field)
2174 for (i = 0; i < type->structure.nfields; i++)
2175 if (text_cmp(type->structure.fields[i].name, field) == 0)
2180 ###### propagate exec cases
2184 struct fieldref *f = cast(fieldref, prog);
2185 struct type *st = propagate_types(f->left, c, ok, NULL, 0);
2188 type_err(c, "error: unknown type for field access", f->left, // UNTESTED
2190 else if (st->init != structure_init)
2191 type_err(c, "error: field reference attempted on %1, not a struct",
2192 f->left, st, 0, NULL);
2193 else if (f->index == -2) {
2194 f->index = find_struct_index(st, f->name);
2196 type_err(c, "error: cannot find requested field in %1",
2197 f->left, st, 0, NULL);
2199 if (f->index >= 0) {
2200 struct type *ft = st->structure.fields[f->index].type;
2201 if (!type_compat(type, ft, rules))
2202 type_err(c, "error: have %1 but need %2", prog,
2209 ###### interp exec cases
2212 struct fieldref *f = cast(fieldref, e);
2214 struct value *lleft = linterp_exec(c, f->left, <ype);
2215 lrv = (void*)lleft->ptr + ltype->structure.fields[f->index].offset;
2216 rvtype = ltype->structure.fields[f->index].type;
2222 struct fieldlist *prev;
2226 ###### ast functions
2227 static void free_fieldlist(struct fieldlist *f)
2231 free_fieldlist(f->prev);
2233 free_value(f->f.type, f->f.init); // UNTESTED
2234 free(f->f.init); // UNTESTED
2239 ###### top level grammar
2240 DeclareStruct -> struct IDENTIFIER FieldBlock Newlines ${ {
2242 add_type(c, $2.txt, &structure_prototype);
2244 struct fieldlist *f;
2246 for (f = $3; f; f=f->prev)
2249 t->structure.nfields = cnt;
2250 t->structure.fields = calloc(cnt, sizeof(struct field));
2253 int a = f->f.type->align;
2255 t->structure.fields[cnt] = f->f;
2256 if (t->size & (a-1))
2257 t->size = (t->size | (a-1)) + 1;
2258 t->structure.fields[cnt].offset = t->size;
2259 t->size += ((f->f.type->size - 1) | (a-1)) + 1;
2268 FieldBlock -> { IN OptNL FieldLines OUT OptNL } ${ $0 = $<FL; }$
2269 | { SimpleFieldList } ${ $0 = $<SFL; }$
2270 | IN OptNL FieldLines OUT ${ $0 = $<FL; }$
2271 | SimpleFieldList EOL ${ $0 = $<SFL; }$
2273 FieldLines -> SimpleFieldList Newlines ${ $0 = $<SFL; }$
2274 | FieldLines SimpleFieldList Newlines ${
2279 SimpleFieldList -> Field ${ $0 = $<F; }$
2280 | SimpleFieldList ; Field ${
2284 | SimpleFieldList ; ${
2287 | ERROR ${ tok_err(c, "Syntax error in struct field", &$1); }$
2289 Field -> IDENTIFIER : Type = Expression ${ {
2292 $0 = calloc(1, sizeof(struct fieldlist));
2293 $0->f.name = $1.txt;
2298 propagate_types($<5, c, &ok, $3, 0);
2301 c->parse_error = 1; // UNTESTED
2303 struct value vl = interp_exec(c, $5, NULL);
2304 $0->f.init = global_alloc(c, $0->f.type, NULL, &vl);
2307 | IDENTIFIER : Type ${
2308 $0 = calloc(1, sizeof(struct fieldlist));
2309 $0->f.name = $1.txt;
2311 if ($0->f.type->prepare_type)
2312 $0->f.type->prepare_type(c, $0->f.type, 1);
2315 ###### forward decls
2316 static void structure_print_type(struct type *t, FILE *f);
2318 ###### value functions
2319 static void structure_print_type(struct type *t, FILE *f) // UNTESTED
2323 fprintf(f, "struct %.*s\n", t->name.len, t->name.txt);
2325 for (i = 0; i < t->structure.nfields; i++) {
2326 struct field *fl = t->structure.fields + i;
2327 fprintf(f, " %.*s : ", fl->name.len, fl->name.txt);
2328 type_print(fl->type, f);
2329 if (fl->type->print && fl->init) {
2331 if (fl->type == Tstr)
2332 fprintf(f, "\""); // UNTESTED
2333 print_value(fl->type, fl->init);
2334 if (fl->type == Tstr)
2335 fprintf(f, "\""); // UNTESTED
2341 ###### print type decls
2343 struct type *t; // UNTESTED
2346 while (target != 0) {
2348 for (t = context.typelist; t ; t=t->next)
2349 if (t->print_type_decl && !t->check_args) {
2358 t->print_type_decl(t, stdout);
2366 A function is a chunk of code which can be passed parameters and can
2367 return results. Each function has a type which includes the set of
2368 parameters and the return value. As yet these types cannot be declared
2369 separately from the function itself.
2371 The parameters can be specified either in parentheses as a ';' separated
2374 ##### Example: function 1
2376 func main(av:[ac::number]string; env:[envc::number]string)
2379 or as an indented list of one parameter per line (though each line can
2380 be a ';' separated list)
2382 ##### Example: function 2
2385 argv:[argc::number]string
2386 env:[envc::number]string
2390 In the first case a return type can follow the paentheses after a colon,
2391 in the second it is given on a line starting with the word `return`.
2393 ##### Example: functions that return
2395 func add(a:number; b:number): number
2406 For constructing these lists we use a `List` binode, which will be
2407 further detailed when Expression Lists are introduced.
2409 ###### type union fields
2412 struct binode *params;
2413 struct type *return_type;
2417 ###### value union fields
2418 struct exec *function;
2420 ###### type functions
2421 void (*check_args)(struct parse_context *c, int *ok,
2422 struct type *require, struct exec *args);
2424 ###### value functions
2426 static void function_free(struct type *type, struct value *val)
2428 free_exec(val->function);
2429 val->function = NULL;
2432 static int function_compat(struct type *require, struct type *have)
2434 // FIXME can I do anything here yet?
2438 static void function_check_args(struct parse_context *c, int *ok,
2439 struct type *require, struct exec *args)
2441 /* This should be 'compat', but we don't have a 'tuple' type to
2442 * hold the type of 'args'
2444 struct binode *arg = cast(binode, args);
2445 struct binode *param = require->function.params;
2448 struct var *pv = cast(var, param->left);
2450 type_err(c, "error: insufficient arguments to function.",
2451 args, NULL, 0, NULL);
2455 propagate_types(arg->left, c, ok, pv->var->type, 0);
2456 param = cast(binode, param->right);
2457 arg = cast(binode, arg->right);
2460 type_err(c, "error: too many arguments to function.",
2461 args, NULL, 0, NULL);
2464 static void function_print(struct type *type, struct value *val)
2466 print_exec(val->function, 1, 0);
2469 static void function_print_type_decl(struct type *type, FILE *f)
2473 for (b = type->function.params; b; b = cast(binode, b->right)) {
2474 struct variable *v = cast(var, b->left)->var;
2475 fprintf(f, "%.*s%s", v->name->name.len, v->name->name.txt,
2476 v->constant ? "::" : ":");
2477 type_print(v->type, f);
2482 if (type->function.return_type != Tnone) {
2484 type_print(type->function.return_type, f);
2489 static void function_free_type(struct type *t)
2491 free_exec(t->function.params);
2494 static struct type function_prototype = {
2495 .size = sizeof(void*),
2496 .align = sizeof(void*),
2497 .free = function_free,
2498 .compat = function_compat,
2499 .check_args = function_check_args,
2500 .print = function_print,
2501 .print_type_decl = function_print_type_decl,
2502 .free_type = function_free_type,
2505 ###### declare terminals
2515 FuncName -> IDENTIFIER ${ {
2516 struct variable *v = var_decl(c, $1.txt);
2517 struct var *e = new_pos(var, $1);
2523 v = var_ref(c, $1.txt);
2525 type_err(c, "error: function '%v' redeclared",
2527 type_err(c, "info: this is where '%v' was first declared",
2528 v->where_decl, NULL, 0, NULL);
2534 Args -> ArgsLine NEWLINE ${ $0 = $<AL; }$
2535 | Args ArgsLine NEWLINE ${ {
2536 struct binode *b = $<AL;
2537 struct binode **bp = &b;
2539 bp = (struct binode **)&(*bp)->left;
2544 ArgsLine -> ${ $0 = NULL; }$
2545 | Varlist ${ $0 = $<1; }$
2546 | Varlist ; ${ $0 = $<1; }$
2548 Varlist -> Varlist ; ArgDecl ${
2562 ArgDecl -> IDENTIFIER : FormalType ${ {
2563 struct variable *v = var_decl(c, $1.txt);
2569 ## Executables: the elements of code
2571 Each code element needs to be parsed, printed, analysed,
2572 interpreted, and freed. There are several, so let's just start with
2573 the easy ones and work our way up.
2577 We have already met values as separate objects. When manifest
2578 constants appear in the program text, that must result in an executable
2579 which has a constant value. So the `val` structure embeds a value in
2592 ###### ast functions
2593 struct val *new_val(struct type *T, struct token tk)
2595 struct val *v = new_pos(val, tk);
2606 $0 = new_val(Tbool, $1);
2610 $0 = new_val(Tbool, $1);
2614 $0 = new_val(Tnum, $1);
2617 if (number_parse($0->val.num, tail, $1.txt) == 0)
2618 mpq_init($0->val.num); // UNTESTED
2620 tok_err(c, "error: unsupported number suffix",
2625 $0 = new_val(Tstr, $1);
2628 string_parse(&$1, '\\', &$0->val.str, tail);
2630 tok_err(c, "error: unsupported string suffix",
2635 $0 = new_val(Tstr, $1);
2638 string_parse(&$1, '\\', &$0->val.str, tail);
2640 tok_err(c, "error: unsupported string suffix",
2645 ###### print exec cases
2648 struct val *v = cast(val, e);
2649 if (v->vtype == Tstr)
2651 print_value(v->vtype, &v->val);
2652 if (v->vtype == Tstr)
2657 ###### propagate exec cases
2660 struct val *val = cast(val, prog);
2661 if (!type_compat(type, val->vtype, rules))
2662 type_err(c, "error: expected %1%r found %2",
2663 prog, type, rules, val->vtype);
2667 ###### interp exec cases
2669 rvtype = cast(val, e)->vtype;
2670 dup_value(rvtype, &cast(val, e)->val, &rv);
2673 ###### ast functions
2674 static void free_val(struct val *v)
2677 free_value(v->vtype, &v->val);
2681 ###### free exec cases
2682 case Xval: free_val(cast(val, e)); break;
2684 ###### ast functions
2685 // Move all nodes from 'b' to 'rv', reversing their order.
2686 // In 'b' 'left' is a list, and 'right' is the last node.
2687 // In 'rv', left' is the first node and 'right' is a list.
2688 static struct binode *reorder_bilist(struct binode *b)
2690 struct binode *rv = NULL;
2693 struct exec *t = b->right;
2697 b = cast(binode, b->left);
2707 Just as we used a `val` to wrap a value into an `exec`, we similarly
2708 need a `var` to wrap a `variable` into an exec. While each `val`
2709 contained a copy of the value, each `var` holds a link to the variable
2710 because it really is the same variable no matter where it appears.
2711 When a variable is used, we need to remember to follow the `->merged`
2712 link to find the primary instance.
2720 struct variable *var;
2728 VariableDecl -> IDENTIFIER : ${ {
2729 struct variable *v = var_decl(c, $1.txt);
2730 $0 = new_pos(var, $1);
2735 v = var_ref(c, $1.txt);
2737 type_err(c, "error: variable '%v' redeclared",
2739 type_err(c, "info: this is where '%v' was first declared",
2740 v->where_decl, NULL, 0, NULL);
2743 | IDENTIFIER :: ${ {
2744 struct variable *v = var_decl(c, $1.txt);
2745 $0 = new_pos(var, $1);
2751 v = var_ref(c, $1.txt);
2753 type_err(c, "error: variable '%v' redeclared",
2755 type_err(c, "info: this is where '%v' was first declared",
2756 v->where_decl, NULL, 0, NULL);
2759 | IDENTIFIER : Type ${ {
2760 struct variable *v = var_decl(c, $1.txt);
2761 $0 = new_pos(var, $1);
2768 v = var_ref(c, $1.txt);
2770 type_err(c, "error: variable '%v' redeclared",
2772 type_err(c, "info: this is where '%v' was first declared",
2773 v->where_decl, NULL, 0, NULL);
2776 | IDENTIFIER :: Type ${ {
2777 struct variable *v = var_decl(c, $1.txt);
2778 $0 = new_pos(var, $1);
2786 v = var_ref(c, $1.txt);
2788 type_err(c, "error: variable '%v' redeclared",
2790 type_err(c, "info: this is where '%v' was first declared",
2791 v->where_decl, NULL, 0, NULL);
2796 Variable -> IDENTIFIER ${ {
2797 struct variable *v = var_ref(c, $1.txt);
2798 $0 = new_pos(var, $1);
2800 /* This might be a label - allocate a var just in case */
2801 v = var_decl(c, $1.txt);
2808 cast(var, $0)->var = v;
2812 ###### print exec cases
2815 struct var *v = cast(var, e);
2817 struct binding *b = v->var->name;
2818 printf("%.*s", b->name.len, b->name.txt);
2825 if (loc && loc->type == Xvar) {
2826 struct var *v = cast(var, loc);
2828 struct binding *b = v->var->name;
2829 fprintf(stderr, "%.*s", b->name.len, b->name.txt);
2831 fputs("???", stderr); // NOTEST
2833 fputs("NOTVAR", stderr);
2836 ###### propagate exec cases
2840 struct var *var = cast(var, prog);
2841 struct variable *v = var->var;
2843 type_err(c, "%d:BUG: no variable!!", prog, NULL, 0, NULL); // NOTEST
2844 return Tnone; // NOTEST
2847 if (v->constant && (rules & Rnoconstant)) {
2848 type_err(c, "error: Cannot assign to a constant: %v",
2849 prog, NULL, 0, NULL);
2850 type_err(c, "info: name was defined as a constant here",
2851 v->where_decl, NULL, 0, NULL);
2854 if (v->type == Tnone && v->where_decl == prog)
2855 type_err(c, "error: variable used but not declared: %v",
2856 prog, NULL, 0, NULL);
2857 if (v->type == NULL) {
2858 if (type && *ok != 0) {
2860 v->where_set = prog;
2865 if (!type_compat(type, v->type, rules)) {
2866 type_err(c, "error: expected %1%r but variable '%v' is %2", prog,
2867 type, rules, v->type);
2868 type_err(c, "info: this is where '%v' was set to %1", v->where_set,
2869 v->type, rules, NULL);
2876 ###### interp exec cases
2879 struct var *var = cast(var, e);
2880 struct variable *v = var->var;
2883 lrv = var_value(c, v);
2888 ###### ast functions
2890 static void free_var(struct var *v)
2895 ###### free exec cases
2896 case Xvar: free_var(cast(var, e)); break;
2898 ### Expressions: Conditional
2900 Our first user of the `binode` will be conditional expressions, which
2901 is a bit odd as they actually have three components. That will be
2902 handled by having 2 binodes for each expression. The conditional
2903 expression is the lowest precedence operator which is why we define it
2904 first - to start the precedence list.
2906 Conditional expressions are of the form "value `if` condition `else`
2907 other_value". They associate to the right, so everything to the right
2908 of `else` is part of an else value, while only a higher-precedence to
2909 the left of `if` is the if values. Between `if` and `else` there is no
2910 room for ambiguity, so a full conditional expression is allowed in
2922 Expression -> Expression if Expression else Expression $$ifelse ${ {
2923 struct binode *b1 = new(binode);
2924 struct binode *b2 = new(binode);
2933 ## expression grammar
2935 ###### print binode cases
2938 b2 = cast(binode, b->right);
2939 if (bracket) printf("(");
2940 print_exec(b2->left, -1, bracket);
2942 print_exec(b->left, -1, bracket);
2944 print_exec(b2->right, -1, bracket);
2945 if (bracket) printf(")");
2948 ###### propagate binode cases
2951 /* cond must be Tbool, others must match */
2952 struct binode *b2 = cast(binode, b->right);
2955 propagate_types(b->left, c, ok, Tbool, 0);
2956 t = propagate_types(b2->left, c, ok, type, Rnolabel);
2957 t2 = propagate_types(b2->right, c, ok, type ?: t, Rnolabel);
2961 ###### interp binode cases
2964 struct binode *b2 = cast(binode, b->right);
2965 left = interp_exec(c, b->left, <ype);
2967 rv = interp_exec(c, b2->left, &rvtype); // UNTESTED
2969 rv = interp_exec(c, b2->right, &rvtype);
2975 We take a brief detour, now that we have expressions, to describe lists
2976 of expressions. These will be needed for function parameters and
2977 possibly other situations. They seem generic enough to introduce here
2978 to be used elsewhere.
2980 And ExpressionList will use the `List` type of `binode`, building up at
2981 the end. And place where they are used will probably call
2982 `reorder_bilist()` to get a more normal first/next arrangement.
2984 ###### declare terminals
2987 `List` execs have no implicit semantics, so they are never propagated or
2988 interpreted. The can be printed as a comma separate list, which is how
2989 they are parsed. Note they are also used for function formal parameter
2990 lists. In that case a separate function is used to print them.
2992 ###### print binode cases
2996 print_exec(b->left, -1, bracket);
2999 b = cast(binode, b->right);
3003 ###### propagate binode cases
3004 case List: abort(); // NOTEST
3005 ###### interp binode cases
3006 case List: abort(); // NOTEST
3011 ExpressionList -> ExpressionList , Expression ${
3024 ### Expressions: Boolean
3026 The next class of expressions to use the `binode` will be Boolean
3027 expressions. "`and then`" and "`or else`" are similar to `and` and `or`
3028 have same corresponding precendence. The difference is that they don't
3029 evaluate the second expression if not necessary.
3038 ###### expr precedence
3043 ###### expression grammar
3044 | Expression or Expression ${ {
3045 struct binode *b = new(binode);
3051 | Expression or else Expression ${ {
3052 struct binode *b = new(binode);
3059 | Expression and Expression ${ {
3060 struct binode *b = new(binode);
3066 | Expression and then Expression ${ {
3067 struct binode *b = new(binode);
3074 | not Expression ${ {
3075 struct binode *b = new(binode);
3081 ###### print binode cases
3083 if (bracket) printf("(");
3084 print_exec(b->left, -1, bracket);
3086 print_exec(b->right, -1, bracket);
3087 if (bracket) printf(")");
3090 if (bracket) printf("(");
3091 print_exec(b->left, -1, bracket);
3092 printf(" and then ");
3093 print_exec(b->right, -1, bracket);
3094 if (bracket) printf(")");
3097 if (bracket) printf("(");
3098 print_exec(b->left, -1, bracket);
3100 print_exec(b->right, -1, bracket);
3101 if (bracket) printf(")");
3104 if (bracket) printf("(");
3105 print_exec(b->left, -1, bracket);
3106 printf(" or else ");
3107 print_exec(b->right, -1, bracket);
3108 if (bracket) printf(")");
3111 if (bracket) printf("(");
3113 print_exec(b->right, -1, bracket);
3114 if (bracket) printf(")");
3117 ###### propagate binode cases
3123 /* both must be Tbool, result is Tbool */
3124 propagate_types(b->left, c, ok, Tbool, 0);
3125 propagate_types(b->right, c, ok, Tbool, 0);
3126 if (type && type != Tbool)
3127 type_err(c, "error: %1 operation found where %2 expected", prog,
3131 ###### interp binode cases
3133 rv = interp_exec(c, b->left, &rvtype);
3134 right = interp_exec(c, b->right, &rtype);
3135 rv.bool = rv.bool && right.bool;
3138 rv = interp_exec(c, b->left, &rvtype);
3140 rv = interp_exec(c, b->right, NULL);
3143 rv = interp_exec(c, b->left, &rvtype);
3144 right = interp_exec(c, b->right, &rtype);
3145 rv.bool = rv.bool || right.bool;
3148 rv = interp_exec(c, b->left, &rvtype);
3150 rv = interp_exec(c, b->right, NULL);
3153 rv = interp_exec(c, b->right, &rvtype);
3157 ### Expressions: Comparison
3159 Of slightly higher precedence that Boolean expressions are Comparisons.
3160 A comparison takes arguments of any comparable type, but the two types
3163 To simplify the parsing we introduce an `eop` which can record an
3164 expression operator, and the `CMPop` non-terminal will match one of them.
3171 ###### ast functions
3172 static void free_eop(struct eop *e)
3186 ###### expr precedence
3187 $LEFT < > <= >= == != CMPop
3189 ###### expression grammar
3190 | Expression CMPop Expression ${ {
3191 struct binode *b = new(binode);
3201 CMPop -> < ${ $0.op = Less; }$
3202 | > ${ $0.op = Gtr; }$
3203 | <= ${ $0.op = LessEq; }$
3204 | >= ${ $0.op = GtrEq; }$
3205 | == ${ $0.op = Eql; }$
3206 | != ${ $0.op = NEql; }$
3208 ###### print binode cases
3216 if (bracket) printf("(");
3217 print_exec(b->left, -1, bracket);
3219 case Less: printf(" < "); break;
3220 case LessEq: printf(" <= "); break;
3221 case Gtr: printf(" > "); break;
3222 case GtrEq: printf(" >= "); break;
3223 case Eql: printf(" == "); break;
3224 case NEql: printf(" != "); break;
3225 default: abort(); // NOTEST
3227 print_exec(b->right, -1, bracket);
3228 if (bracket) printf(")");
3231 ###### propagate binode cases
3238 /* Both must match but not be labels, result is Tbool */
3239 t = propagate_types(b->left, c, ok, NULL, Rnolabel);
3241 propagate_types(b->right, c, ok, t, 0);
3243 t = propagate_types(b->right, c, ok, NULL, Rnolabel); // UNTESTED
3245 t = propagate_types(b->left, c, ok, t, 0); // UNTESTED
3247 if (!type_compat(type, Tbool, 0))
3248 type_err(c, "error: Comparison returns %1 but %2 expected", prog,
3249 Tbool, rules, type);
3252 ###### interp binode cases
3261 left = interp_exec(c, b->left, <ype);
3262 right = interp_exec(c, b->right, &rtype);
3263 cmp = value_cmp(ltype, rtype, &left, &right);
3266 case Less: rv.bool = cmp < 0; break;
3267 case LessEq: rv.bool = cmp <= 0; break;
3268 case Gtr: rv.bool = cmp > 0; break;
3269 case GtrEq: rv.bool = cmp >= 0; break;
3270 case Eql: rv.bool = cmp == 0; break;
3271 case NEql: rv.bool = cmp != 0; break;
3272 default: rv.bool = 0; break; // NOTEST
3277 ### Expressions: Arithmetic etc.
3279 The remaining expressions with the highest precedence are arithmetic,
3280 string concatenation, and string conversion. String concatenation
3281 (`++`) has the same precedence as multiplication and division, but lower
3284 String conversion is a temporary feature until I get a better type
3285 system. `$` is a prefix operator which expects a string and returns
3288 `+` and `-` are both infix and prefix operations (where they are
3289 absolute value and negation). These have different operator names.
3291 We also have a 'Bracket' operator which records where parentheses were
3292 found. This makes it easy to reproduce these when printing. Possibly I
3293 should only insert brackets were needed for precedence.
3303 ###### expr precedence
3309 ###### expression grammar
3310 | Expression Eop Expression ${ {
3311 struct binode *b = new(binode);
3318 | Expression Top Expression ${ {
3319 struct binode *b = new(binode);
3326 | ( Expression ) ${ {
3327 struct binode *b = new_pos(binode, $1);
3332 | Uop Expression ${ {
3333 struct binode *b = new(binode);
3338 | Value ${ $0 = $<1; }$
3339 | Variable ${ $0 = $<1; }$
3344 Eop -> + ${ $0.op = Plus; }$
3345 | - ${ $0.op = Minus; }$
3347 Uop -> + ${ $0.op = Absolute; }$
3348 | - ${ $0.op = Negate; }$
3349 | $ ${ $0.op = StringConv; }$
3351 Top -> * ${ $0.op = Times; }$
3352 | / ${ $0.op = Divide; }$
3353 | % ${ $0.op = Rem; }$
3354 | ++ ${ $0.op = Concat; }$
3356 ###### print binode cases
3363 if (bracket) printf("(");
3364 print_exec(b->left, indent, bracket);
3366 case Plus: fputs(" + ", stdout); break;
3367 case Minus: fputs(" - ", stdout); break;
3368 case Times: fputs(" * ", stdout); break;
3369 case Divide: fputs(" / ", stdout); break;
3370 case Rem: fputs(" % ", stdout); break;
3371 case Concat: fputs(" ++ ", stdout); break;
3372 default: abort(); // NOTEST
3374 print_exec(b->right, indent, bracket);
3375 if (bracket) printf(")");
3380 if (bracket) printf("(");
3382 case Absolute: fputs("+", stdout); break;
3383 case Negate: fputs("-", stdout); break;
3384 case StringConv: fputs("$", stdout); break;
3385 default: abort(); // NOTEST
3387 print_exec(b->right, indent, bracket);
3388 if (bracket) printf(")");
3392 print_exec(b->right, indent, bracket);
3396 ###### propagate binode cases
3402 /* both must be numbers, result is Tnum */
3405 /* as propagate_types ignores a NULL,
3406 * unary ops fit here too */
3407 propagate_types(b->left, c, ok, Tnum, 0);
3408 propagate_types(b->right, c, ok, Tnum, 0);
3409 if (!type_compat(type, Tnum, 0))
3410 type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
3415 /* both must be Tstr, result is Tstr */
3416 propagate_types(b->left, c, ok, Tstr, 0);
3417 propagate_types(b->right, c, ok, Tstr, 0);
3418 if (!type_compat(type, Tstr, 0))
3419 type_err(c, "error: Concat returns %1 but %2 expected", prog,
3424 /* op must be string, result is number */
3425 propagate_types(b->left, c, ok, Tstr, 0);
3426 if (!type_compat(type, Tnum, 0))
3427 type_err(c, // UNTESTED
3428 "error: Can only convert string to number, not %1",
3429 prog, type, 0, NULL);
3433 return propagate_types(b->right, c, ok, type, 0);
3435 ###### interp binode cases
3438 rv = interp_exec(c, b->left, &rvtype);
3439 right = interp_exec(c, b->right, &rtype);
3440 mpq_add(rv.num, rv.num, right.num);
3443 rv = interp_exec(c, b->left, &rvtype);
3444 right = interp_exec(c, b->right, &rtype);
3445 mpq_sub(rv.num, rv.num, right.num);
3448 rv = interp_exec(c, b->left, &rvtype);
3449 right = interp_exec(c, b->right, &rtype);
3450 mpq_mul(rv.num, rv.num, right.num);
3453 rv = interp_exec(c, b->left, &rvtype);
3454 right = interp_exec(c, b->right, &rtype);
3455 mpq_div(rv.num, rv.num, right.num);
3460 left = interp_exec(c, b->left, <ype);
3461 right = interp_exec(c, b->right, &rtype);
3462 mpz_init(l); mpz_init(r); mpz_init(rem);
3463 mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
3464 mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
3465 mpz_tdiv_r(rem, l, r);
3466 val_init(Tnum, &rv);
3467 mpq_set_z(rv.num, rem);
3468 mpz_clear(r); mpz_clear(l); mpz_clear(rem);
3473 rv = interp_exec(c, b->right, &rvtype);
3474 mpq_neg(rv.num, rv.num);
3477 rv = interp_exec(c, b->right, &rvtype);
3478 mpq_abs(rv.num, rv.num);
3481 rv = interp_exec(c, b->right, &rvtype);
3484 left = interp_exec(c, b->left, <ype);
3485 right = interp_exec(c, b->right, &rtype);
3487 rv.str = text_join(left.str, right.str);
3490 right = interp_exec(c, b->right, &rvtype);
3494 struct text tx = right.str;
3497 if (tx.txt[0] == '-') {
3498 neg = 1; // UNTESTED
3499 tx.txt++; // UNTESTED
3500 tx.len--; // UNTESTED
3502 if (number_parse(rv.num, tail, tx) == 0)
3503 mpq_init(rv.num); // UNTESTED
3505 mpq_neg(rv.num, rv.num); // UNTESTED
3507 printf("Unsupported suffix: %.*s\n", tx.len, tx.txt); // UNTESTED
3511 ###### value functions
3513 static struct text text_join(struct text a, struct text b)
3516 rv.len = a.len + b.len;
3517 rv.txt = malloc(rv.len);
3518 memcpy(rv.txt, a.txt, a.len);
3519 memcpy(rv.txt+a.len, b.txt, b.len);
3525 A function call can appear either as an expression or as a statement.
3526 As functions cannot yet return values, only the statement version will work.
3527 We use a new 'Funcall' binode type to link the function with a list of
3528 arguments, form with the 'List' nodes.
3533 ###### expression grammar
3534 | Variable ( ExpressionList ) ${ {
3535 struct binode *b = new(binode);
3538 b->right = reorder_bilist($<EL);
3542 struct binode *b = new(binode);
3549 ###### SimpleStatement Grammar
3551 | Variable ( ExpressionList ) ${ {
3552 struct binode *b = new(binode);
3555 b->right = reorder_bilist($<EL);
3559 ###### print binode cases
3562 do_indent(indent, "");
3563 print_exec(b->left, -1, bracket);
3565 for (b = cast(binode, b->right); b; b = cast(binode, b->right)) {
3568 print_exec(b->left, -1, bracket);
3578 ###### propagate binode cases
3581 /* Every arg must match formal parameter, and result
3582 * is return type of function
3584 struct binode *args = cast(binode, b->right);
3585 struct var *v = cast(var, b->left);
3587 if (!v->var->type || v->var->type->check_args == NULL) {
3588 type_err(c, "error: attempt to call a non-function.",
3589 prog, NULL, 0, NULL);
3592 v->var->type->check_args(c, ok, v->var->type, args);
3593 return v->var->type->function.return_type;
3596 ###### interp binode cases
3599 struct var *v = cast(var, b->left);
3600 struct type *t = v->var->type;
3601 void *oldlocal = c->local;
3602 int old_size = c->local_size;
3603 void *local = calloc(1, t->function.local_size);
3604 struct value *fbody = var_value(c, v->var);
3605 struct binode *arg = cast(binode, b->right);
3606 struct binode *param = t->function.params;
3609 struct var *pv = cast(var, param->left);
3610 struct type *vtype = NULL;
3611 struct value val = interp_exec(c, arg->left, &vtype);
3613 c->local = local; c->local_size = t->function.local_size;
3614 lval = var_value(c, pv->var);
3615 c->local = oldlocal; c->local_size = old_size;
3616 memcpy(lval, &val, vtype->size);
3617 param = cast(binode, param->right);
3618 arg = cast(binode, arg->right);
3620 c->local = local; c->local_size = t->function.local_size;
3621 rv = interp_exec(c, fbody->function, &rvtype);
3622 c->local = oldlocal; c->local_size = old_size;
3627 ### Blocks, Statements, and Statement lists.
3629 Now that we have expressions out of the way we need to turn to
3630 statements. There are simple statements and more complex statements.
3631 Simple statements do not contain (syntactic) newlines, complex statements do.
3633 Statements often come in sequences and we have corresponding simple
3634 statement lists and complex statement lists.
3635 The former comprise only simple statements separated by semicolons.
3636 The later comprise complex statements and simple statement lists. They are
3637 separated by newlines. Thus the semicolon is only used to separate
3638 simple statements on the one line. This may be overly restrictive,
3639 but I'm not sure I ever want a complex statement to share a line with
3642 Note that a simple statement list can still use multiple lines if
3643 subsequent lines are indented, so
3645 ###### Example: wrapped simple statement list
3650 is a single simple statement list. This might allow room for
3651 confusion, so I'm not set on it yet.
3653 A simple statement list needs no extra syntax. A complex statement
3654 list has two syntactic forms. It can be enclosed in braces (much like
3655 C blocks), or it can be introduced by an indent and continue until an
3656 unindented newline (much like Python blocks). With this extra syntax
3657 it is referred to as a block.
3659 Note that a block does not have to include any newlines if it only
3660 contains simple statements. So both of:
3662 if condition: a=b; d=f
3664 if condition { a=b; print f }
3668 In either case the list is constructed from a `binode` list with
3669 `Block` as the operator. When parsing the list it is most convenient
3670 to append to the end, so a list is a list and a statement. When using
3671 the list it is more convenient to consider a list to be a statement
3672 and a list. So we need a function to re-order a list.
3673 `reorder_bilist` serves this purpose.
3675 The only stand-alone statement we introduce at this stage is `pass`
3676 which does nothing and is represented as a `NULL` pointer in a `Block`
3677 list. Other stand-alone statements will follow once the infrastructure
3688 Block -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3689 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3690 | SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3691 | SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3692 | IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3694 OpenBlock -> OpenScope { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3695 | OpenScope { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3696 | OpenScope SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3697 | OpenScope SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3698 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3700 UseBlock -> { OpenScope IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3701 | { OpenScope SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3702 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3704 ColonBlock -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3705 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3706 | : SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3707 | : SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3708 | : IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3710 Statementlist -> ComplexStatements ${ $0 = reorder_bilist($<CS); }$
3712 ComplexStatements -> ComplexStatements ComplexStatement ${
3722 | ComplexStatement ${
3734 ComplexStatement -> SimpleStatements Newlines ${
3735 $0 = reorder_bilist($<SS);
3737 | SimpleStatements ; Newlines ${
3738 $0 = reorder_bilist($<SS);
3740 ## ComplexStatement Grammar
3743 SimpleStatements -> SimpleStatements ; SimpleStatement ${
3749 | SimpleStatement ${
3757 SimpleStatement -> pass ${ $0 = NULL; }$
3758 | ERROR ${ tok_err(c, "Syntax error in statement", &$1); }$
3759 ## SimpleStatement Grammar
3761 ###### print binode cases
3765 if (b->left == NULL) // UNTESTED
3766 printf("pass"); // UNTESTED
3768 print_exec(b->left, indent, bracket); // UNTESTED
3769 if (b->right) { // UNTESTED
3770 printf("; "); // UNTESTED
3771 print_exec(b->right, indent, bracket); // UNTESTED
3774 // block, one per line
3775 if (b->left == NULL)
3776 do_indent(indent, "pass\n");
3778 print_exec(b->left, indent, bracket);
3780 print_exec(b->right, indent, bracket);
3784 ###### propagate binode cases
3787 /* If any statement returns something other than Tnone
3788 * or Tbool then all such must return same type.
3789 * As each statement may be Tnone or something else,
3790 * we must always pass NULL (unknown) down, otherwise an incorrect
3791 * error might occur. We never return Tnone unless it is
3796 for (e = b; e; e = cast(binode, e->right)) {
3797 t = propagate_types(e->left, c, ok, NULL, rules);
3798 if ((rules & Rboolok) && (t == Tbool || t == Tnone))
3800 if (t == Tnone && e->right)
3801 /* Only the final statement *must* return a value
3809 type_err(c, "error: expected %1%r, found %2",
3810 e->left, type, rules, t);
3816 ###### interp binode cases
3818 while (rvtype == Tnone &&
3821 rv = interp_exec(c, b->left, &rvtype);
3822 b = cast(binode, b->right);
3826 ### The Print statement
3828 `print` is a simple statement that takes a comma-separated list of
3829 expressions and prints the values separated by spaces and terminated
3830 by a newline. No control of formatting is possible.
3832 `print` uses `ExpressionList` to collect the expressions and stores them
3833 on the left side of a `Print` binode unlessthere is a trailing comma
3834 when the list is stored on the `right` side and no trailing newline is
3840 ##### expr precedence
3843 ###### SimpleStatement Grammar
3845 | print ExpressionList ${
3849 $0->left = reorder_bilist($<EL);
3851 | print ExpressionList , ${ {
3854 $0->right = reorder_bilist($<EL);
3864 ###### print binode cases
3867 do_indent(indent, "print");
3869 print_exec(b->right, -1, bracket);
3872 print_exec(b->left, -1, bracket);
3877 ###### propagate binode cases
3880 /* don't care but all must be consistent */
3882 b = cast(binode, b->left);
3884 b = cast(binode, b->right);
3886 propagate_types(b->left, c, ok, NULL, Rnolabel);
3887 b = cast(binode, b->right);
3891 ###### interp binode cases
3895 struct binode *b2 = cast(binode, b->left);
3897 b2 = cast(binode, b->right);
3898 for (; b2; b2 = cast(binode, b2->right)) {
3899 left = interp_exec(c, b2->left, <ype);
3900 print_value(ltype, &left);
3901 free_value(ltype, &left);
3905 if (b->right == NULL)
3911 ###### Assignment statement
3913 An assignment will assign a value to a variable, providing it hasn't
3914 been declared as a constant. The analysis phase ensures that the type
3915 will be correct so the interpreter just needs to perform the
3916 calculation. There is a form of assignment which declares a new
3917 variable as well as assigning a value. If a name is assigned before
3918 it is declared, and error will be raised as the name is created as
3919 `Tlabel` and it is illegal to assign to such names.
3925 ###### declare terminals
3928 ###### SimpleStatement Grammar
3929 | Variable = Expression ${
3935 | VariableDecl = Expression ${
3943 if ($1->var->where_set == NULL) {
3945 "Variable declared with no type or value: %v",
3956 ###### print binode cases
3959 do_indent(indent, "");
3960 print_exec(b->left, indent, bracket);
3962 print_exec(b->right, indent, bracket);
3969 struct variable *v = cast(var, b->left)->var;
3970 do_indent(indent, "");
3971 print_exec(b->left, indent, bracket);
3972 if (cast(var, b->left)->var->constant) {
3974 if (v->where_decl == v->where_set) {
3975 type_print(v->type, stdout);
3980 if (v->where_decl == v->where_set) {
3981 type_print(v->type, stdout);
3987 print_exec(b->right, indent, bracket);
3994 ###### propagate binode cases
3998 /* Both must match and not be labels,
3999 * Type must support 'dup',
4000 * For Assign, left must not be constant.
4003 t = propagate_types(b->left, c, ok, NULL,
4004 Rnolabel | (b->op == Assign ? Rnoconstant : 0));
4009 if (propagate_types(b->right, c, ok, t, 0) != t)
4010 if (b->left->type == Xvar)
4011 type_err(c, "info: variable '%v' was set as %1 here.",
4012 cast(var, b->left)->var->where_set, t, rules, NULL);
4014 t = propagate_types(b->right, c, ok, NULL, Rnolabel);
4016 propagate_types(b->left, c, ok, t,
4017 (b->op == Assign ? Rnoconstant : 0));
4019 if (t && t->dup == NULL)
4020 type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
4025 ###### interp binode cases
4028 lleft = linterp_exec(c, b->left, <ype);
4030 dinterp_exec(c, b->right, lleft, ltype, 1);
4036 struct variable *v = cast(var, b->left)->var;
4039 val = var_value(c, v);
4040 if (v->type->prepare_type)
4041 v->type->prepare_type(c, v->type, 0);
4043 dinterp_exec(c, b->right, val, v->type, 0);
4045 val_init(v->type, val);
4049 ### The `use` statement
4051 The `use` statement is the last "simple" statement. It is needed when a
4052 statement block can return a value. This includes the body of a
4053 function which has a return type, and the "condition" code blocks in
4054 `if`, `while`, and `switch` statements.
4059 ###### expr precedence
4062 ###### SimpleStatement Grammar
4064 $0 = new_pos(binode, $1);
4067 if ($0->right->type == Xvar) {
4068 struct var *v = cast(var, $0->right);
4069 if (v->var->type == Tnone) {
4070 /* Convert this to a label */
4073 v->var->type = Tlabel;
4074 val = global_alloc(c, Tlabel, v->var, NULL);
4080 ###### print binode cases
4083 do_indent(indent, "use ");
4084 print_exec(b->right, -1, bracket);
4089 ###### propagate binode cases
4092 /* result matches value */
4093 return propagate_types(b->right, c, ok, type, 0);
4095 ###### interp binode cases
4098 rv = interp_exec(c, b->right, &rvtype);
4101 ### The Conditional Statement
4103 This is the biggy and currently the only complex statement. This
4104 subsumes `if`, `while`, `do/while`, `switch`, and some parts of `for`.
4105 It is comprised of a number of parts, all of which are optional though
4106 set combinations apply. Each part is (usually) a key word (`then` is
4107 sometimes optional) followed by either an expression or a code block,
4108 except the `casepart` which is a "key word and an expression" followed
4109 by a code block. The code-block option is valid for all parts and,
4110 where an expression is also allowed, the code block can use the `use`
4111 statement to report a value. If the code block does not report a value
4112 the effect is similar to reporting `True`.
4114 The `else` and `case` parts, as well as `then` when combined with
4115 `if`, can contain a `use` statement which will apply to some
4116 containing conditional statement. `for` parts, `do` parts and `then`
4117 parts used with `for` can never contain a `use`, except in some
4118 subordinate conditional statement.
4120 If there is a `forpart`, it is executed first, only once.
4121 If there is a `dopart`, then it is executed repeatedly providing
4122 always that the `condpart` or `cond`, if present, does not return a non-True
4123 value. `condpart` can fail to return any value if it simply executes
4124 to completion. This is treated the same as returning `True`.
4126 If there is a `thenpart` it will be executed whenever the `condpart`
4127 or `cond` returns True (or does not return any value), but this will happen
4128 *after* `dopart` (when present).
4130 If `elsepart` is present it will be executed at most once when the
4131 condition returns `False` or some value that isn't `True` and isn't
4132 matched by any `casepart`. If there are any `casepart`s, they will be
4133 executed when the condition returns a matching value.
4135 The particular sorts of values allowed in case parts has not yet been
4136 determined in the language design, so nothing is prohibited.
4138 The various blocks in this complex statement potentially provide scope
4139 for variables as described earlier. Each such block must include the
4140 "OpenScope" nonterminal before parsing the block, and must call
4141 `var_block_close()` when closing the block.
4143 The code following "`if`", "`switch`" and "`for`" does not get its own
4144 scope, but is in a scope covering the whole statement, so names
4145 declared there cannot be redeclared elsewhere. Similarly the
4146 condition following "`while`" is in a scope the covers the body
4147 ("`do`" part) of the loop, and which does not allow conditional scope
4148 extension. Code following "`then`" (both looping and non-looping),
4149 "`else`" and "`case`" each get their own local scope.
4151 The type requirements on the code block in a `whilepart` are quite
4152 unusal. It is allowed to return a value of some identifiable type, in
4153 which case the loop aborts and an appropriate `casepart` is run, or it
4154 can return a Boolean, in which case the loop either continues to the
4155 `dopart` (on `True`) or aborts and runs the `elsepart` (on `False`).
4156 This is different both from the `ifpart` code block which is expected to
4157 return a Boolean, or the `switchpart` code block which is expected to
4158 return the same type as the casepart values. The correct analysis of
4159 the type of the `whilepart` code block is the reason for the
4160 `Rboolok` flag which is passed to `propagate_types()`.
4162 The `cond_statement` cannot fit into a `binode` so a new `exec` is
4163 defined. As there are two scopes which cover multiple parts - one for
4164 the whole statement and one for "while" and "do" - and as we will use
4165 the 'struct exec' to track scopes, we actually need two new types of
4166 exec. One is a `binode` for the looping part, the rest is the
4167 `cond_statement`. The `cond_statement` will use an auxilliary `struct
4168 casepart` to track a list of case parts.
4179 struct exec *action;
4180 struct casepart *next;
4182 struct cond_statement {
4184 struct exec *forpart, *condpart, *thenpart, *elsepart;
4185 struct binode *looppart;
4186 struct casepart *casepart;
4189 ###### ast functions
4191 static void free_casepart(struct casepart *cp)
4195 free_exec(cp->value);
4196 free_exec(cp->action);
4203 static void free_cond_statement(struct cond_statement *s)
4207 free_exec(s->forpart);
4208 free_exec(s->condpart);
4209 free_exec(s->looppart);
4210 free_exec(s->thenpart);
4211 free_exec(s->elsepart);
4212 free_casepart(s->casepart);
4216 ###### free exec cases
4217 case Xcond_statement: free_cond_statement(cast(cond_statement, e)); break;
4219 ###### ComplexStatement Grammar
4220 | CondStatement ${ $0 = $<1; }$
4222 ###### expr precedence
4223 $TERM for then while do
4230 // A CondStatement must end with EOL, as does CondSuffix and
4232 // ForPart, ThenPart, SwitchPart, CasePart are non-empty and
4233 // may or may not end with EOL
4234 // WhilePart and IfPart include an appropriate Suffix
4236 // ForPart, SwitchPart, and IfPart open scopes, o we have to close
4237 // them. WhilePart opens and closes its own scope.
4238 CondStatement -> ForPart OptNL ThenPart OptNL WhilePart CondSuffix ${
4241 $0->thenpart = $<TP;
4242 $0->looppart = $<WP;
4243 var_block_close(c, CloseSequential, $0);
4245 | ForPart OptNL WhilePart CondSuffix ${
4248 $0->looppart = $<WP;
4249 var_block_close(c, CloseSequential, $0);
4251 | WhilePart CondSuffix ${
4253 $0->looppart = $<WP;
4255 | SwitchPart OptNL CasePart CondSuffix ${
4257 $0->condpart = $<SP;
4258 $CP->next = $0->casepart;
4259 $0->casepart = $<CP;
4260 var_block_close(c, CloseSequential, $0);
4262 | SwitchPart : IN OptNL CasePart CondSuffix OUT Newlines ${
4264 $0->condpart = $<SP;
4265 $CP->next = $0->casepart;
4266 $0->casepart = $<CP;
4267 var_block_close(c, CloseSequential, $0);
4269 | IfPart IfSuffix ${
4271 $0->condpart = $IP.condpart; $IP.condpart = NULL;
4272 $0->thenpart = $IP.thenpart; $IP.thenpart = NULL;
4273 // This is where we close an "if" statement
4274 var_block_close(c, CloseSequential, $0);
4277 CondSuffix -> IfSuffix ${
4280 | Newlines CasePart CondSuffix ${
4282 $CP->next = $0->casepart;
4283 $0->casepart = $<CP;
4285 | CasePart CondSuffix ${
4287 $CP->next = $0->casepart;
4288 $0->casepart = $<CP;
4291 IfSuffix -> Newlines ${ $0 = new(cond_statement); }$
4292 | Newlines ElsePart ${ $0 = $<EP; }$
4293 | ElsePart ${$0 = $<EP; }$
4295 ElsePart -> else OpenBlock Newlines ${
4296 $0 = new(cond_statement);
4297 $0->elsepart = $<OB;
4298 var_block_close(c, CloseElse, $0->elsepart);
4300 | else OpenScope CondStatement ${
4301 $0 = new(cond_statement);
4302 $0->elsepart = $<CS;
4303 var_block_close(c, CloseElse, $0->elsepart);
4307 CasePart -> case Expression OpenScope ColonBlock ${
4308 $0 = calloc(1,sizeof(struct casepart));
4311 var_block_close(c, CloseParallel, $0->action);
4315 // These scopes are closed in CondStatement
4316 ForPart -> for OpenBlock ${
4320 ThenPart -> then OpenBlock ${
4322 var_block_close(c, CloseSequential, $0);
4326 // This scope is closed in CondStatement
4327 WhilePart -> while UseBlock OptNL do OpenBlock ${
4332 var_block_close(c, CloseSequential, $0->right);
4333 var_block_close(c, CloseSequential, $0);
4335 | while OpenScope Expression OpenScope ColonBlock ${
4340 var_block_close(c, CloseSequential, $0->right);
4341 var_block_close(c, CloseSequential, $0);
4345 IfPart -> if UseBlock OptNL then OpenBlock ${
4348 var_block_close(c, CloseParallel, $0.thenpart);
4350 | if OpenScope Expression OpenScope ColonBlock ${
4353 var_block_close(c, CloseParallel, $0.thenpart);
4355 | if OpenScope Expression OpenScope OptNL then Block ${
4358 var_block_close(c, CloseParallel, $0.thenpart);
4362 // This scope is closed in CondStatement
4363 SwitchPart -> switch OpenScope Expression ${
4366 | switch UseBlock ${
4370 ###### print binode cases
4372 if (b->left && b->left->type == Xbinode &&
4373 cast(binode, b->left)->op == Block) {
4375 do_indent(indent, "while {\n");
4377 do_indent(indent, "while\n");
4378 print_exec(b->left, indent+1, bracket);
4380 do_indent(indent, "} do {\n");
4382 do_indent(indent, "do\n");
4383 print_exec(b->right, indent+1, bracket);
4385 do_indent(indent, "}\n");
4387 do_indent(indent, "while ");
4388 print_exec(b->left, 0, bracket);
4393 print_exec(b->right, indent+1, bracket);
4395 do_indent(indent, "}\n");
4399 ###### print exec cases
4401 case Xcond_statement:
4403 struct cond_statement *cs = cast(cond_statement, e);
4404 struct casepart *cp;
4406 do_indent(indent, "for");
4407 if (bracket) printf(" {\n"); else printf("\n");
4408 print_exec(cs->forpart, indent+1, bracket);
4411 do_indent(indent, "} then {\n");
4413 do_indent(indent, "then\n");
4414 print_exec(cs->thenpart, indent+1, bracket);
4416 if (bracket) do_indent(indent, "}\n");
4419 print_exec(cs->looppart, indent, bracket);
4423 do_indent(indent, "switch");
4425 do_indent(indent, "if");
4426 if (cs->condpart && cs->condpart->type == Xbinode &&
4427 cast(binode, cs->condpart)->op == Block) {
4432 print_exec(cs->condpart, indent+1, bracket);
4434 do_indent(indent, "}\n");
4436 do_indent(indent, "then\n");
4437 print_exec(cs->thenpart, indent+1, bracket);
4441 print_exec(cs->condpart, 0, bracket);
4447 print_exec(cs->thenpart, indent+1, bracket);
4449 do_indent(indent, "}\n");
4454 for (cp = cs->casepart; cp; cp = cp->next) {
4455 do_indent(indent, "case ");
4456 print_exec(cp->value, -1, 0);
4461 print_exec(cp->action, indent+1, bracket);
4463 do_indent(indent, "}\n");
4466 do_indent(indent, "else");
4471 print_exec(cs->elsepart, indent+1, bracket);
4473 do_indent(indent, "}\n");
4478 ###### propagate binode cases
4480 t = propagate_types(b->right, c, ok, Tnone, 0);
4481 if (!type_compat(Tnone, t, 0))
4482 *ok = 0; // UNTESTED
4483 return propagate_types(b->left, c, ok, type, rules);
4485 ###### propagate exec cases
4486 case Xcond_statement:
4488 // forpart and looppart->right must return Tnone
4489 // thenpart must return Tnone if there is a loopart,
4490 // otherwise it is like elsepart.
4492 // be bool if there is no casepart
4493 // match casepart->values if there is a switchpart
4494 // either be bool or match casepart->value if there
4496 // elsepart and casepart->action must match the return type
4497 // expected of this statement.
4498 struct cond_statement *cs = cast(cond_statement, prog);
4499 struct casepart *cp;
4501 t = propagate_types(cs->forpart, c, ok, Tnone, 0);
4502 if (!type_compat(Tnone, t, 0))
4503 *ok = 0; // UNTESTED
4506 t = propagate_types(cs->thenpart, c, ok, Tnone, 0);
4507 if (!type_compat(Tnone, t, 0))
4508 *ok = 0; // UNTESTED
4510 if (cs->casepart == NULL) {
4511 propagate_types(cs->condpart, c, ok, Tbool, 0);
4512 propagate_types(cs->looppart, c, ok, Tbool, 0);
4514 /* Condpart must match case values, with bool permitted */
4516 for (cp = cs->casepart;
4517 cp && !t; cp = cp->next)
4518 t = propagate_types(cp->value, c, ok, NULL, 0);
4519 if (!t && cs->condpart)
4520 t = propagate_types(cs->condpart, c, ok, NULL, Rboolok); // UNTESTED
4521 if (!t && cs->looppart)
4522 t = propagate_types(cs->looppart, c, ok, NULL, Rboolok); // UNTESTED
4523 // Now we have a type (I hope) push it down
4525 for (cp = cs->casepart; cp; cp = cp->next)
4526 propagate_types(cp->value, c, ok, t, 0);
4527 propagate_types(cs->condpart, c, ok, t, Rboolok);
4528 propagate_types(cs->looppart, c, ok, t, Rboolok);
4531 // (if)then, else, and case parts must return expected type.
4532 if (!cs->looppart && !type)
4533 type = propagate_types(cs->thenpart, c, ok, NULL, rules);
4535 type = propagate_types(cs->elsepart, c, ok, NULL, rules);
4536 for (cp = cs->casepart;
4538 cp = cp->next) // UNTESTED
4539 type = propagate_types(cp->action, c, ok, NULL, rules); // UNTESTED
4542 propagate_types(cs->thenpart, c, ok, type, rules);
4543 propagate_types(cs->elsepart, c, ok, type, rules);
4544 for (cp = cs->casepart; cp ; cp = cp->next)
4545 propagate_types(cp->action, c, ok, type, rules);
4551 ###### interp binode cases
4553 // This just performs one iterration of the loop
4554 rv = interp_exec(c, b->left, &rvtype);
4555 if (rvtype == Tnone ||
4556 (rvtype == Tbool && rv.bool != 0))
4557 // rvtype is Tnone or Tbool, doesn't need to be freed
4558 interp_exec(c, b->right, NULL);
4561 ###### interp exec cases
4562 case Xcond_statement:
4564 struct value v, cnd;
4565 struct type *vtype, *cndtype;
4566 struct casepart *cp;
4567 struct cond_statement *cs = cast(cond_statement, e);
4570 interp_exec(c, cs->forpart, NULL);
4572 while ((cnd = interp_exec(c, cs->looppart, &cndtype)),
4573 cndtype == Tnone || (cndtype == Tbool && cnd.bool != 0))
4574 interp_exec(c, cs->thenpart, NULL);
4576 cnd = interp_exec(c, cs->condpart, &cndtype);
4577 if ((cndtype == Tnone ||
4578 (cndtype == Tbool && cnd.bool != 0))) {
4579 // cnd is Tnone or Tbool, doesn't need to be freed
4580 rv = interp_exec(c, cs->thenpart, &rvtype);
4581 // skip else (and cases)
4585 for (cp = cs->casepart; cp; cp = cp->next) {
4586 v = interp_exec(c, cp->value, &vtype);
4587 if (value_cmp(cndtype, vtype, &v, &cnd) == 0) {
4588 free_value(vtype, &v);
4589 free_value(cndtype, &cnd);
4590 rv = interp_exec(c, cp->action, &rvtype);
4593 free_value(vtype, &v);
4595 free_value(cndtype, &cnd);
4597 rv = interp_exec(c, cs->elsepart, &rvtype);
4604 ### Top level structure
4606 All the language elements so far can be used in various places. Now
4607 it is time to clarify what those places are.
4609 At the top level of a file there will be a number of declarations.
4610 Many of the things that can be declared haven't been described yet,
4611 such as functions, procedures, imports, and probably more.
4612 For now there are two sorts of things that can appear at the top
4613 level. They are predefined constants, `struct` types, and the `main`
4614 function. While the syntax will allow the `main` function to appear
4615 multiple times, that will trigger an error if it is actually attempted.
4617 The various declarations do not return anything. They store the
4618 various declarations in the parse context.
4620 ###### Parser: grammar
4623 Ocean -> OptNL DeclarationList
4625 ## declare terminals
4632 DeclarationList -> Declaration
4633 | DeclarationList Declaration
4635 Declaration -> ERROR Newlines ${
4636 tok_err(c, // UNTESTED
4637 "error: unhandled parse error", &$1);
4643 ## top level grammar
4647 ### The `const` section
4649 As well as being defined in with the code that uses them, constants
4650 can be declared at the top level. These have full-file scope, so they
4651 are always `InScope`. The value of a top level constant can be given
4652 as an expression, and this is evaluated immediately rather than in the
4653 later interpretation stage. Once we add functions to the language, we
4654 will need rules concern which, if any, can be used to define a top
4657 Constants are defined in a section that starts with the reserved word
4658 `const` and then has a block with a list of assignment statements.
4659 For syntactic consistency, these must use the double-colon syntax to
4660 make it clear that they are constants. Type can also be given: if
4661 not, the type will be determined during analysis, as with other
4664 As the types constants are inserted at the head of a list, printing
4665 them in the same order that they were read is not straight forward.
4666 We take a quadratic approach here and count the number of constants
4667 (variables of depth 0), then count down from there, each time
4668 searching through for the Nth constant for decreasing N.
4670 ###### top level grammar
4674 DeclareConstant -> const { IN OptNL ConstList OUT OptNL } Newlines
4675 | const { SimpleConstList } Newlines
4676 | const IN OptNL ConstList OUT Newlines
4677 | const SimpleConstList Newlines
4679 ConstList -> ConstList SimpleConstLine
4681 SimpleConstList -> SimpleConstList ; Const
4684 SimpleConstLine -> SimpleConstList Newlines
4685 | ERROR Newlines ${ tok_err(c, "Syntax error in constant", &$1); }$
4688 CType -> Type ${ $0 = $<1; }$
4691 Const -> IDENTIFIER :: CType = Expression ${ {
4695 v = var_decl(c, $1.txt);
4697 struct var *var = new_pos(var, $1);
4698 v->where_decl = var;
4704 struct variable *vorig = var_ref(c, $1.txt);
4705 tok_err(c, "error: name already declared", &$1);
4706 type_err(c, "info: this is where '%v' was first declared",
4707 vorig->where_decl, NULL, 0, NULL);
4711 propagate_types($5, c, &ok, $3, 0);
4716 struct value res = interp_exec(c, $5, &v->type);
4717 global_alloc(c, v->type, v, &res);
4721 ###### print const decls
4726 while (target != 0) {
4728 for (v = context.in_scope; v; v=v->in_scope)
4729 if (v->depth == 0 && v->constant) {
4740 struct value *val = var_value(&context, v);
4741 printf(" %.*s :: ", v->name->name.len, v->name->name.txt);
4742 type_print(v->type, stdout);
4744 if (v->type == Tstr)
4746 print_value(v->type, val);
4747 if (v->type == Tstr)
4755 ### Function declarations
4757 The code in an Ocean program is all stored in function declarations.
4758 One of the functions must be named `main` and it must accept an array of
4759 strings as a parameter - the command line arguments.
4761 As this is the top level, several things are handled a bit differently.
4762 The function is not interpreted by `interp_exec` as that isn't passed
4763 the argument list which the program requires. Similarly type analysis
4764 is a bit more interesting at this level.
4766 ###### ast functions
4768 static struct variable *declare_function(struct parse_context *c,
4769 struct variable *name,
4770 struct binode *args,
4774 struct text funcname = {" func", 5};
4776 struct value fn = {.function = code};
4777 name->type = add_type(c, funcname, &function_prototype);
4778 name->type->function.params = reorder_bilist(args);
4779 name->type->function.return_type = ret;
4780 global_alloc(c, name->type, name, &fn);
4781 var_block_close(c, CloseSequential, code);
4786 var_block_close(c, CloseSequential, NULL);
4791 ###### declare terminals
4794 ###### top level grammar
4797 DeclareFunction -> func FuncName ( OpenScope ArgsLine ) Block Newlines ${
4798 $0 = declare_function(c, $<FN, $<Ar, Tnone, $<Bl);
4800 | func FuncName IN OpenScope Args OUT OptNL do Block Newlines ${
4801 $0 = declare_function(c, $<FN, $<Ar, Tnone, $<Bl);
4803 | func FuncName NEWLINE OpenScope OptNL do Block Newlines ${
4804 $0 = declare_function(c, $<FN, NULL, Tnone, $<Bl);
4806 | func FuncName ( OpenScope ArgsLine ) : Type Block Newlines ${
4807 $0 = declare_function(c, $<FN, $<Ar, $<Ty, $<Bl);
4809 | func FuncName IN OpenScope Args OUT OptNL return Type Newlines do Block Newlines ${
4810 $0 = declare_function(c, $<FN, $<Ar, $<Ty, $<Bl);
4812 | func FuncName NEWLINE OpenScope return Type Newlines do Block Newlines ${
4813 $0 = declare_function(c, $<FN, NULL, $<Ty, $<Bl);
4816 ###### print func decls
4821 while (target != 0) {
4823 for (v = context.in_scope; v; v=v->in_scope)
4824 if (v->depth == 0 && v->type && v->type->check_args) {
4833 struct value *val = var_value(&context, v);
4834 printf("func %.*s", v->name->name.len, v->name->name.txt);
4835 v->type->print_type_decl(v->type, stdout);
4837 print_exec(val->function, 0, brackets);
4839 print_value(v->type, val);
4840 printf("/* frame size %d */\n", v->type->function.local_size);
4846 ###### core functions
4848 static int analyse_funcs(struct parse_context *c)
4852 for (v = c->in_scope; v; v = v->in_scope) {
4855 if (v->depth != 0 || !v->type || !v->type->check_args)
4857 val = var_value(c, v);
4860 propagate_types(val->function, c, &ok,
4861 v->type->function.return_type, 0);
4864 /* Make sure everything is still consistent */
4865 propagate_types(val->function, c, &ok,
4866 v->type->function.return_type, 0);
4869 if (!v->type->function.return_type->dup) {
4870 type_err(c, "error: function cannot return value of type %1",
4871 v->where_decl, v->type->function.return_type, 0, NULL);
4874 v->type->function.local_size = scope_finalize(c);
4879 static int analyse_main(struct type *type, struct parse_context *c)
4881 struct binode *bp = type->function.params;
4885 struct type *argv_type;
4886 struct text argv_type_name = { " argv", 5 };
4888 argv_type = add_type(c, argv_type_name, &array_prototype);
4889 argv_type->array.member = Tstr;
4890 argv_type->array.unspec = 1;
4892 for (b = bp; b; b = cast(binode, b->right)) {
4896 propagate_types(b->left, c, &ok, argv_type, 0);
4898 default: /* invalid */ // NOTEST
4899 propagate_types(b->left, c, &ok, Tnone, 0); // NOTEST
4905 return !c->parse_error;
4908 static void interp_main(struct parse_context *c, int argc, char **argv)
4910 struct value *progp = NULL;
4911 struct text main_name = { "main", 4 };
4912 struct variable *mainv;
4918 mainv = var_ref(c, main_name);
4920 progp = var_value(c, mainv);
4921 if (!progp || !progp->function) {
4922 fprintf(stderr, "oceani: no main function found.\n");
4926 if (!analyse_main(mainv->type, c)) {
4927 fprintf(stderr, "oceani: main has wrong type.\n");
4931 al = mainv->type->function.params;
4933 c->local_size = mainv->type->function.local_size;
4934 c->local = calloc(1, c->local_size);
4936 struct var *v = cast(var, al->left);
4937 struct value *vl = var_value(c, v->var);
4947 mpq_set_ui(argcq, argc, 1);
4948 memcpy(var_value(c, t->array.vsize), &argcq, sizeof(argcq));
4949 t->prepare_type(c, t, 0);
4950 array_init(v->var->type, vl);
4951 for (i = 0; i < argc; i++) {
4952 struct value *vl2 = vl->array + i * v->var->type->array.member->size;
4954 arg.str.txt = argv[i];
4955 arg.str.len = strlen(argv[i]);
4956 free_value(Tstr, vl2);
4957 dup_value(Tstr, &arg, vl2);
4961 al = cast(binode, al->right);
4963 v = interp_exec(c, progp->function, &vtype);
4964 free_value(vtype, &v);
4969 ###### ast functions
4970 void free_variable(struct variable *v)
4974 ## And now to test it out.
4976 Having a language requires having a "hello world" program. I'll
4977 provide a little more than that: a program that prints "Hello world"
4978 finds the GCD of two numbers, prints the first few elements of
4979 Fibonacci, performs a binary search for a number, and a few other
4980 things which will likely grow as the languages grows.
4982 ###### File: oceani.mk
4985 @echo "===== DEMO ====="
4986 ./oceani --section "demo: hello" oceani.mdc 55 33
4992 four ::= 2 + 2 ; five ::= 10/2
4993 const pie ::= "I like Pie";
4994 cake ::= "The cake is"
5002 func main(argv:[argc::]string)
5003 print "Hello World, what lovely oceans you have!"
5004 print "Are there", five, "?"
5005 print pi, pie, "but", cake
5007 A := $argv[1]; B := $argv[2]
5009 /* When a variable is defined in both branches of an 'if',
5010 * and used afterwards, the variables are merged.
5016 print "Is", A, "bigger than", B,"? ", bigger
5017 /* If a variable is not used after the 'if', no
5018 * merge happens, so types can be different
5021 double:string = "yes"
5022 print A, "is more than twice", B, "?", double
5025 print "double", B, "is", double
5030 if a > 0 and then b > 0:
5036 print "GCD of", A, "and", B,"is", a
5038 print a, "is not positive, cannot calculate GCD"
5040 print b, "is not positive, cannot calculate GCD"
5045 print "Fibonacci:", f1,f2,
5046 then togo = togo - 1
5054 /* Binary search... */
5059 mid := (lo + hi) / 2
5072 print "Yay, I found", target
5074 print "Closest I found was", lo
5079 // "middle square" PRNG. Not particularly good, but one my
5080 // Dad taught me - the first one I ever heard of.
5081 for i:=1; then i = i + 1; while i < size:
5082 n := list[i-1] * list[i-1]
5083 list[i] = (n / 100) % 10 000
5085 print "Before sort:",
5086 for i:=0; then i = i + 1; while i < size:
5090 for i := 1; then i=i+1; while i < size:
5091 for j:=i-1; then j=j-1; while j >= 0:
5092 if list[j] > list[j+1]:
5096 print " After sort:",
5097 for i:=0; then i = i + 1; while i < size:
5101 if 1 == 2 then print "yes"; else print "no"
5105 bob.alive = (bob.name == "Hello")
5106 print "bob", "is" if bob.alive else "isn't", "alive"