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;
123 #define container_of(ptr, type, member) ({ \
124 const typeof( ((type *)0)->member ) *__mptr = (ptr); \
125 (type *)( (char *)__mptr - offsetof(type,member) );})
127 #define config2context(_conf) container_of(_conf, struct parse_context, \
130 ###### Parser: reduce
131 struct parse_context *c = config2context(config);
139 #include <sys/mman.h>
158 static char Usage[] =
159 "Usage: oceani --trace --print --noexec --brackets --section=SectionName prog.ocn\n";
160 static const struct option long_options[] = {
161 {"trace", 0, NULL, 't'},
162 {"print", 0, NULL, 'p'},
163 {"noexec", 0, NULL, 'n'},
164 {"brackets", 0, NULL, 'b'},
165 {"section", 1, NULL, 's'},
168 const char *options = "tpnbs";
170 static void pr_err(char *msg) // NOTEST
172 fprintf(stderr, "%s\n", msg); // NOTEST
175 int main(int argc, char *argv[])
180 struct section *s, *ss;
181 char *section = NULL;
182 struct parse_context context = {
184 .ignored = (1 << TK_mark),
185 .number_chars = ".,_+- ",
190 int doprint=0, dotrace=0, doexec=1, brackets=0;
192 while ((opt = getopt_long(argc, argv, options, long_options, NULL))
195 case 't': dotrace=1; break;
196 case 'p': doprint=1; break;
197 case 'n': doexec=0; break;
198 case 'b': brackets=1; break;
199 case 's': section = optarg; break;
200 default: fprintf(stderr, Usage);
204 if (optind >= argc) {
205 fprintf(stderr, "oceani: no input file given\n");
208 fd = open(argv[optind], O_RDONLY);
210 fprintf(stderr, "oceani: cannot open %s\n", argv[optind]);
213 context.file_name = argv[optind];
214 len = lseek(fd, 0, 2);
215 file = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
216 s = code_extract(file, file+len, pr_err);
218 fprintf(stderr, "oceani: could not find any code in %s\n",
223 ## context initialization
226 for (ss = s; ss; ss = ss->next) {
227 struct text sec = ss->section;
228 if (sec.len == strlen(section) &&
229 strncmp(sec.txt, section, sec.len) == 0)
233 fprintf(stderr, "oceani: cannot find section %s\n",
239 parse_oceani(ss->code, &context.config, dotrace ? stderr : NULL);
242 fprintf(stderr, "oceani: no main function found.\n");
243 context.parse_error = 1;
245 if (context.prog && !context.parse_error) {
246 if (!analyse_prog(context.prog, &context)) {
247 fprintf(stderr, "oceani: type error in program - not running.\n");
248 context.parse_error = 1;
251 if (context.prog && doprint) {
254 print_exec(context.prog, 0, brackets);
256 if (context.prog && doexec && !context.parse_error)
257 interp_prog(&context, context.prog, argc - optind, argv+optind);
258 free_exec(context.prog);
261 struct section *t = s->next;
267 ## free context types
268 ## free context storage
269 exit(context.parse_error ? 1 : 0);
274 The four requirements of parse, analyse, print, interpret apply to
275 each language element individually so that is how most of the code
278 Three of the four are fairly self explanatory. The one that requires
279 a little explanation is the analysis step.
281 The current language design does not require the types of variables to
282 be declared, but they must still have a single type. Different
283 operations impose different requirements on the variables, for example
284 addition requires both arguments to be numeric, and assignment
285 requires the variable on the left to have the same type as the
286 expression on the right.
288 Analysis involves propagating these type requirements around and
289 consequently setting the type of each variable. If any requirements
290 are violated (e.g. a string is compared with a number) or if a
291 variable needs to have two different types, then an error is raised
292 and the program will not run.
294 If the same variable is declared in both branchs of an 'if/else', or
295 in all cases of a 'switch' then the multiple instances may be merged
296 into just one variable if the variable is referenced after the
297 conditional statement. When this happens, the types must naturally be
298 consistent across all the branches. When the variable is not used
299 outside the if, the variables in the different branches are distinct
300 and can be of different types.
302 Undeclared names may only appear in "use" statements and "case" expressions.
303 These names are given a type of "label" and a unique value.
304 This allows them to fill the role of a name in an enumerated type, which
305 is useful for testing the `switch` statement.
307 As we will see, the condition part of a `while` statement can return
308 either a Boolean or some other type. This requires that the expected
309 type that gets passed around comprises a type and a flag to indicate
310 that `Tbool` is also permitted.
312 As there are, as yet, no distinct types that are compatible, there
313 isn't much subtlety in the analysis. When we have distinct number
314 types, this will become more interesting.
318 When analysis discovers an inconsistency it needs to report an error;
319 just refusing to run the code ensures that the error doesn't cascade,
320 but by itself it isn't very useful. A clear understanding of the sort
321 of error message that are useful will help guide the process of
324 At a simplistic level, the only sort of error that type analysis can
325 report is that the type of some construct doesn't match a contextual
326 requirement. For example, in `4 + "hello"` the addition provides a
327 contextual requirement for numbers, but `"hello"` is not a number. In
328 this particular example no further information is needed as the types
329 are obvious from local information. When a variable is involved that
330 isn't the case. It may be helpful to explain why the variable has a
331 particular type, by indicating the location where the type was set,
332 whether by declaration or usage.
334 Using a recursive-descent analysis we can easily detect a problem at
335 multiple locations. In "`hello:= "there"; 4 + hello`" the addition
336 will detect that one argument is not a number and the usage of `hello`
337 will detect that a number was wanted, but not provided. In this
338 (early) version of the language, we will generate error reports at
339 multiple locations, so the use of `hello` will report an error and
340 explain were the value was set, and the addition will report an error
341 and say why numbers are needed. To be able to report locations for
342 errors, each language element will need to record a file location
343 (line and column) and each variable will need to record the language
344 element where its type was set. For now we will assume that each line
345 of an error message indicates one location in the file, and up to 2
346 types. So we provide a `printf`-like function which takes a format, a
347 location (a `struct exec` which has not yet been introduced), and 2
348 types. "`%1`" reports the first type, "`%2`" reports the second. We
349 will need a function to print the location, once we know how that is
350 stored. e As will be explained later, there are sometimes extra rules for
351 type matching and they might affect error messages, we need to pass those
354 As well as type errors, we sometimes need to report problems with
355 tokens, which might be unexpected or might name a type that has not
356 been defined. For these we have `tok_err()` which reports an error
357 with a given token. Each of the error functions sets the flag in the
358 context so indicate that parsing failed.
362 static void fput_loc(struct exec *loc, FILE *f);
364 ###### core functions
366 static void type_err(struct parse_context *c,
367 char *fmt, struct exec *loc,
368 struct type *t1, int rules, struct type *t2)
370 fprintf(stderr, "%s:", c->file_name);
371 fput_loc(loc, stderr);
372 for (; *fmt ; fmt++) {
379 case '%': fputc(*fmt, stderr); break; // NOTEST
380 default: fputc('?', stderr); break; // NOTEST
382 type_print(t1, stderr);
385 type_print(t2, stderr);
394 static void tok_err(struct parse_context *c, char *fmt, struct token *t)
396 fprintf(stderr, "%s:%d:%d: %s: %.*s\n", c->file_name, t->line, t->col, fmt,
397 t->txt.len, t->txt.txt);
401 ## Entities: declared and predeclared.
403 There are various "things" that the language and/or the interpreter
404 needs to know about to parse and execute a program. These include
405 types, variables, values, and executable code. These are all lumped
406 together under the term "entities" (calling them "objects" would be
407 confusing) and introduced here. The following section will present the
408 different specific code elements which comprise or manipulate these
413 Values come in a wide range of types, with more likely to be added.
414 Each type needs to be able to print its own values (for convenience at
415 least) as well as to compare two values, at least for equality and
416 possibly for order. For now, values might need to be duplicated and
417 freed, though eventually such manipulations will be better integrated
420 Rather than requiring every numeric type to support all numeric
421 operations (add, multiple, etc), we allow types to be able to present
422 as one of a few standard types: integer, float, and fraction. The
423 existence of these conversion functions eventually enable types to
424 determine if they are compatible with other types, though such types
425 have not yet been implemented.
427 Named type are stored in a simple linked list. Objects of each type are
428 "values" which are often passed around by value.
435 ## value union fields
443 void (*init)(struct type *type, struct value *val);
444 void (*prepare_type)(struct parse_context *c, struct type *type, int parse_time);
445 void (*print)(struct type *type, struct value *val);
446 void (*print_type)(struct type *type, FILE *f);
447 int (*cmp_order)(struct type *t1, struct type *t2,
448 struct value *v1, struct value *v2);
449 int (*cmp_eq)(struct type *t1, struct type *t2,
450 struct value *v1, struct value *v2);
451 void (*dup)(struct type *type, struct value *vold, struct value *vnew);
452 void (*free)(struct type *type, struct value *val);
453 void (*free_type)(struct type *t);
454 long long (*to_int)(struct value *v);
455 double (*to_float)(struct value *v);
456 int (*to_mpq)(mpq_t *q, struct value *v);
465 struct type *typelist;
469 static struct type *find_type(struct parse_context *c, struct text s)
471 struct type *l = c->typelist;
474 text_cmp(l->name, s) != 0)
479 static struct type *add_type(struct parse_context *c, struct text s,
484 n = calloc(1, sizeof(*n));
487 n->next = c->typelist;
492 static void free_type(struct type *t)
494 /* The type is always a reference to something in the
495 * context, so we don't need to free anything.
499 static void free_value(struct type *type, struct value *v)
505 static void type_print(struct type *type, FILE *f)
508 fputs("*unknown*type*", f); // NOTEST
509 else if (type->name.len)
510 fprintf(f, "%.*s", type->name.len, type->name.txt);
511 else if (type->print_type)
512 type->print_type(type, f);
514 fputs("*invalid*type*", f); // NOTEST
517 static void val_init(struct type *type, struct value *val)
519 if (type && type->init)
520 type->init(type, val);
523 static void dup_value(struct type *type,
524 struct value *vold, struct value *vnew)
526 if (type && type->dup)
527 type->dup(type, vold, vnew);
530 static int value_cmp(struct type *tl, struct type *tr,
531 struct value *left, struct value *right)
533 if (tl && tl->cmp_order)
534 return tl->cmp_order(tl, tr, left, right);
535 if (tl && tl->cmp_eq) // NOTEST
536 return tl->cmp_eq(tl, tr, left, right); // NOTEST
540 static void print_value(struct type *type, struct value *v)
542 if (type && type->print)
543 type->print(type, v);
545 printf("*Unknown*"); // NOTEST
550 static void free_value(struct type *type, struct value *v);
551 static int type_compat(struct type *require, struct type *have, int rules);
552 static void type_print(struct type *type, FILE *f);
553 static void val_init(struct type *type, struct value *v);
554 static void dup_value(struct type *type,
555 struct value *vold, struct value *vnew);
556 static int value_cmp(struct type *tl, struct type *tr,
557 struct value *left, struct value *right);
558 static void print_value(struct type *type, struct value *v);
560 ###### free context types
562 while (context.typelist) {
563 struct type *t = context.typelist;
565 context.typelist = t->next;
571 Type can be specified for local variables, for fields in a structure,
572 for formal parameters to functions, and possibly elsewhere. Different
573 rules may apply in different contexts. As a minimum, a named type may
574 always be used. Currently the type of a formal parameter can be
575 different from types in other contexts, so we have a separate grammar
581 Type -> IDENTIFIER ${
582 $0 = find_type(c, $1.txt);
585 "error: undefined type", &$1);
592 FormalType -> Type ${ $0 = $<1; }$
593 ## formal type grammar
597 Values of the base types can be numbers, which we represent as
598 multi-precision fractions, strings, Booleans and labels. When
599 analysing the program we also need to allow for places where no value
600 is meaningful (type `Tnone`) and where we don't know what type to
601 expect yet (type is `NULL`).
603 Values are never shared, they are always copied when used, and freed
604 when no longer needed.
606 When propagating type information around the program, we need to
607 determine if two types are compatible, where type `NULL` is compatible
608 with anything. There are two special cases with type compatibility,
609 both related to the Conditional Statement which will be described
610 later. In some cases a Boolean can be accepted as well as some other
611 primary type, and in others any type is acceptable except a label (`Vlabel`).
612 A separate function encoding these cases will simplify some code later.
614 ###### type functions
616 int (*compat)(struct type *this, struct type *other);
620 static int type_compat(struct type *require, struct type *have, int rules)
622 if ((rules & Rboolok) && have == Tbool)
624 if ((rules & Rnolabel) && have == Tlabel)
626 if (!require || !have)
630 return require->compat(require, have);
632 return require == have;
637 #include "parse_string.h"
638 #include "parse_number.h"
641 myLDLIBS := libnumber.o libstring.o -lgmp
642 LDLIBS := $(filter-out $(myLDLIBS),$(LDLIBS)) $(myLDLIBS)
644 ###### type union fields
645 enum vtype {Vnone, Vstr, Vnum, Vbool, Vlabel} vtype;
647 ###### value union fields
654 static void _free_value(struct type *type, struct value *v)
658 switch (type->vtype) {
660 case Vstr: free(v->str.txt); break;
661 case Vnum: mpq_clear(v->num); break;
667 ###### value functions
669 static void _val_init(struct type *type, struct value *val)
671 switch(type->vtype) {
672 case Vnone: // NOTEST
675 mpq_init(val->num); break;
677 val->str.txt = malloc(1);
689 static void _dup_value(struct type *type,
690 struct value *vold, struct value *vnew)
692 switch (type->vtype) {
693 case Vnone: // NOTEST
696 vnew->label = vold->label;
699 vnew->bool = vold->bool;
703 mpq_set(vnew->num, vold->num);
706 vnew->str.len = vold->str.len;
707 vnew->str.txt = malloc(vnew->str.len);
708 memcpy(vnew->str.txt, vold->str.txt, vnew->str.len);
713 static int _value_cmp(struct type *tl, struct type *tr,
714 struct value *left, struct value *right)
718 return tl - tr; // NOTEST
720 case Vlabel: cmp = left->label == right->label ? 0 : 1; break;
721 case Vnum: cmp = mpq_cmp(left->num, right->num); break;
722 case Vstr: cmp = text_cmp(left->str, right->str); break;
723 case Vbool: cmp = left->bool - right->bool; break;
724 case Vnone: cmp = 0; // NOTEST
729 static void _print_value(struct type *type, struct value *v)
731 switch (type->vtype) {
732 case Vnone: // NOTEST
733 printf("*no-value*"); break; // NOTEST
734 case Vlabel: // NOTEST
735 printf("*label-%p*", v->label); break; // NOTEST
737 printf("%.*s", v->str.len, v->str.txt); break;
739 printf("%s", v->bool ? "True":"False"); break;
744 mpf_set_q(fl, v->num);
745 gmp_printf("%Fg", fl);
752 static void _free_value(struct type *type, struct value *v);
754 static struct type base_prototype = {
756 .print = _print_value,
757 .cmp_order = _value_cmp,
758 .cmp_eq = _value_cmp,
763 static struct type *Tbool, *Tstr, *Tnum, *Tnone, *Tlabel;
766 static struct type *add_base_type(struct parse_context *c, char *n,
767 enum vtype vt, int size)
769 struct text txt = { n, strlen(n) };
772 t = add_type(c, txt, &base_prototype);
775 t->align = size > sizeof(void*) ? sizeof(void*) : size;
776 if (t->size & (t->align - 1))
777 t->size = (t->size | (t->align - 1)) + 1; // NOTEST
781 ###### context initialization
783 Tbool = add_base_type(&context, "Boolean", Vbool, sizeof(char));
784 Tstr = add_base_type(&context, "string", Vstr, sizeof(struct text));
785 Tnum = add_base_type(&context, "number", Vnum, sizeof(mpq_t));
786 Tnone = add_base_type(&context, "none", Vnone, 0);
787 Tlabel = add_base_type(&context, "label", Vlabel, sizeof(void*));
791 Variables are scoped named values. We store the names in a linked list
792 of "bindings" sorted in lexical order, and use sequential search and
799 struct binding *next; // in lexical order
803 This linked list is stored in the parse context so that "reduce"
804 functions can find or add variables, and so the analysis phase can
805 ensure that every variable gets a type.
809 struct binding *varlist; // In lexical order
813 static struct binding *find_binding(struct parse_context *c, struct text s)
815 struct binding **l = &c->varlist;
820 (cmp = text_cmp((*l)->name, s)) < 0)
824 n = calloc(1, sizeof(*n));
831 Each name can be linked to multiple variables defined in different
832 scopes. Each scope starts where the name is declared and continues
833 until the end of the containing code block. Scopes of a given name
834 cannot nest, so a declaration while a name is in-scope is an error.
836 ###### binding fields
837 struct variable *var;
841 struct variable *previous;
843 struct binding *name;
844 struct exec *where_decl;// where name was declared
845 struct exec *where_set; // where type was set
849 While the naming seems strange, we include local constants in the
850 definition of variables. A name declared `var := value` can
851 subsequently be changed, but a name declared `var ::= value` cannot -
854 ###### variable fields
857 Scopes in parallel branches can be partially merged. More
858 specifically, if a given name is declared in both branches of an
859 if/else then its scope is a candidate for merging. Similarly if
860 every branch of an exhaustive switch (e.g. has an "else" clause)
861 declares a given name, then the scopes from the branches are
862 candidates for merging.
864 Note that names declared inside a loop (which is only parallel to
865 itself) are never visible after the loop. Similarly names defined in
866 scopes which are not parallel, such as those started by `for` and
867 `switch`, are never visible after the scope. Only variables defined in
868 both `then` and `else` (including the implicit then after an `if`, and
869 excluding `then` used with `for`) and in all `case`s and `else` of a
870 `switch` or `while` can be visible beyond the `if`/`switch`/`while`.
872 Labels, which are a bit like variables, follow different rules.
873 Labels are not explicitly declared, but if an undeclared name appears
874 in a context where a label is legal, that effectively declares the
875 name as a label. The declaration remains in force (or in scope) at
876 least to the end of the immediately containing block and conditionally
877 in any larger containing block which does not declare the name in some
878 other way. Importantly, the conditional scope extension happens even
879 if the label is only used in one parallel branch of a conditional --
880 when used in one branch it is treated as having been declared in all
883 Merge candidates are tentatively visible beyond the end of the
884 branching statement which creates them. If the name is used, the
885 merge is affirmed and they become a single variable visible at the
886 outer layer. If not - if it is redeclared first - the merge lapses.
888 To track scopes we have an extra stack, implemented as a linked list,
889 which roughly parallels the parse stack and which is used exclusively
890 for scoping. When a new scope is opened, a new frame is pushed and
891 the child-count of the parent frame is incremented. This child-count
892 is used to distinguish between the first of a set of parallel scopes,
893 in which declared variables must not be in scope, and subsequent
894 branches, whether they may already be conditionally scoped.
896 To push a new frame *before* any code in the frame is parsed, we need a
897 grammar reduction. This is most easily achieved with a grammar
898 element which derives the empty string, and creates the new scope when
899 it is recognised. This can be placed, for example, between a keyword
900 like "if" and the code following it.
904 struct scope *parent;
910 struct scope *scope_stack;
913 static void scope_pop(struct parse_context *c)
915 struct scope *s = c->scope_stack;
917 c->scope_stack = s->parent;
922 static void scope_push(struct parse_context *c)
924 struct scope *s = calloc(1, sizeof(*s));
926 c->scope_stack->child_count += 1;
927 s->parent = c->scope_stack;
935 OpenScope -> ${ scope_push(c); }$
937 Each variable records a scope depth and is in one of four states:
939 - "in scope". This is the case between the declaration of the
940 variable and the end of the containing block, and also between
941 the usage with affirms a merge and the end of that block.
943 The scope depth is not greater than the current parse context scope
944 nest depth. When the block of that depth closes, the state will
945 change. To achieve this, all "in scope" variables are linked
946 together as a stack in nesting order.
948 - "pending". The "in scope" block has closed, but other parallel
949 scopes are still being processed. So far, every parallel block at
950 the same level that has closed has declared the name.
952 The scope depth is the depth of the last parallel block that
953 enclosed the declaration, and that has closed.
955 - "conditionally in scope". The "in scope" block and all parallel
956 scopes have closed, and no further mention of the name has been seen.
957 This state includes a secondary nest depth (`min_depth`) which records
958 the outermost scope seen since the variable became conditionally in
959 scope. If a use of the name is found, the variable becomes "in scope"
960 and that secondary depth becomes the recorded scope depth. If the
961 name is declared as a new variable, the old variable becomes "out of
962 scope" and the recorded scope depth stays unchanged.
964 - "out of scope". The variable is neither in scope nor conditionally
965 in scope. It is permanently out of scope now and can be removed from
966 the "in scope" stack.
968 ###### variable fields
969 int depth, min_depth;
970 enum { OutScope, PendingScope, CondScope, InScope } scope;
971 struct variable *in_scope;
975 struct variable *in_scope;
977 All variables with the same name are linked together using the
978 'previous' link. Those variable that have been affirmatively merged all
979 have a 'merged' pointer that points to one primary variable - the most
980 recently declared instance. When merging variables, we need to also
981 adjust the 'merged' pointer on any other variables that had previously
982 been merged with the one that will no longer be primary.
984 A variable that is no longer the most recent instance of a name may
985 still have "pending" scope, if it might still be merged with most
986 recent instance. These variables don't really belong in the
987 "in_scope" list, but are not immediately removed when a new instance
988 is found. Instead, they are detected and ignored when considering the
989 list of in_scope names.
991 The storage of the value of a variable will be described later. For now
992 we just need to know that when a variable goes out of scope, it might
993 need to be freed. For this we need to be able to find it, so assume that
994 `var_value()` will provide that.
996 ###### variable fields
997 struct variable *merged;
1001 static void variable_merge(struct variable *primary, struct variable *secondary)
1005 primary = primary->merged;
1007 for (v = primary->previous; v; v=v->previous)
1008 if (v == secondary || v == secondary->merged ||
1009 v->merged == secondary ||
1010 v->merged == secondary->merged) {
1011 v->scope = OutScope;
1012 v->merged = primary;
1016 ###### forward decls
1017 static struct value *var_value(struct parse_context *c, struct variable *v);
1019 ###### free context vars
1021 while (context.varlist) {
1022 struct binding *b = context.varlist;
1023 struct variable *v = b->var;
1024 context.varlist = b->next;
1027 struct variable *t = v;
1030 free_value(t->type, var_value(&context, t));
1032 // This is a global constant
1033 free_exec(t->where_decl);
1038 #### Manipulating Bindings
1040 When a name is conditionally visible, a new declaration discards the
1041 old binding - the condition lapses. Conversely a usage of the name
1042 affirms the visibility and extends it to the end of the containing
1043 block - i.e. the block that contains both the original declaration and
1044 the latest usage. This is determined from `min_depth`. When a
1045 conditionally visible variable gets affirmed like this, it is also
1046 merged with other conditionally visible variables with the same name.
1048 When we parse a variable declaration we either report an error if the
1049 name is currently bound, or create a new variable at the current nest
1050 depth if the name is unbound or bound to a conditionally scoped or
1051 pending-scope variable. If the previous variable was conditionally
1052 scoped, it and its homonyms becomes out-of-scope.
1054 When we parse a variable reference (including non-declarative assignment
1055 "foo = bar") we report an error if the name is not bound or is bound to
1056 a pending-scope variable; update the scope if the name is bound to a
1057 conditionally scoped variable; or just proceed normally if the named
1058 variable is in scope.
1060 When we exit a scope, any variables bound at this level are either
1061 marked out of scope or pending-scoped, depending on whether the scope
1062 was sequential or parallel. Here a "parallel" scope means the "then"
1063 or "else" part of a conditional, or any "case" or "else" branch of a
1064 switch. Other scopes are "sequential".
1066 When exiting a parallel scope we check if there are any variables that
1067 were previously pending and are still visible. If there are, then
1068 there weren't redeclared in the most recent scope, so they cannot be
1069 merged and must become out-of-scope. If it is not the first of
1070 parallel scopes (based on `child_count`), we check that there was a
1071 previous binding that is still pending-scope. If there isn't, the new
1072 variable must now be out-of-scope.
1074 When exiting a sequential scope that immediately enclosed parallel
1075 scopes, we need to resolve any pending-scope variables. If there was
1076 no `else` clause, and we cannot determine that the `switch` was exhaustive,
1077 we need to mark all pending-scope variable as out-of-scope. Otherwise
1078 all pending-scope variables become conditionally scoped.
1081 enum closetype { CloseSequential, CloseParallel, CloseElse };
1083 ###### ast functions
1085 static struct variable *var_decl(struct parse_context *c, struct text s)
1087 struct binding *b = find_binding(c, s);
1088 struct variable *v = b->var;
1090 switch (v ? v->scope : OutScope) {
1092 /* Caller will report the error */
1096 v && v->scope == CondScope;
1098 v->scope = OutScope;
1102 v = calloc(1, sizeof(*v));
1103 v->previous = b->var;
1107 v->min_depth = v->depth = c->scope_depth;
1109 v->in_scope = c->in_scope;
1114 static struct variable *var_ref(struct parse_context *c, struct text s)
1116 struct binding *b = find_binding(c, s);
1117 struct variable *v = b->var;
1118 struct variable *v2;
1120 switch (v ? v->scope : OutScope) {
1123 /* Caller will report the error */
1126 /* All CondScope variables of this name need to be merged
1127 * and become InScope
1129 v->depth = v->min_depth;
1131 for (v2 = v->previous;
1132 v2 && v2->scope == CondScope;
1134 variable_merge(v, v2);
1142 static void var_block_close(struct parse_context *c, enum closetype ct)
1144 /* Close off all variables that are in_scope.
1145 * Some variables in c->scope may already be not-in-scope,
1146 * such as when a PendingScope variable is hidden by a new
1147 * variable with the same name.
1148 * So we check for v->name->var != v and drop them.
1149 * If we choose to make a variable OutScope, we drop it
1152 struct variable *v, **vp, *v2;
1155 for (vp = &c->in_scope;
1156 (v = *vp) && v->min_depth > c->scope_depth;
1157 (v->scope == OutScope || v->name->var != v)
1158 ? (*vp = v->in_scope, 0)
1159 : ( vp = &v->in_scope, 0)) {
1160 v->min_depth = c->scope_depth;
1161 if (v->name->var != v)
1162 /* This is still in scope, but we haven't just
1168 case CloseParallel: /* handle PendingScope */
1172 if (c->scope_stack->child_count == 1)
1173 /* first among parallel branches */
1174 v->scope = PendingScope;
1175 else if (v->previous &&
1176 v->previous->scope == PendingScope)
1177 /* all previous branches used name */
1178 v->scope = PendingScope;
1179 else if (v->type == Tlabel)
1180 /* Labels remain pending even when not used */
1181 v->scope = PendingScope; // UNTESTED
1183 v->scope = OutScope;
1184 if (ct == CloseElse) {
1185 /* All Pending variables with this name
1186 * are now Conditional */
1188 v2 && v2->scope == PendingScope;
1190 v2->scope = CondScope;
1194 /* Not possible as it would require
1195 * parallel scope to be nested immediately
1196 * in a parallel scope, and that never
1200 /* Not possible as we already tested for
1206 case CloseSequential:
1207 if (v->type == Tlabel)
1208 v->scope = PendingScope;
1211 v->scope = OutScope;
1214 /* There was no 'else', so we can only become
1215 * conditional if we know the cases were exhaustive,
1216 * and that doesn't mean anything yet.
1217 * So only labels become conditional..
1220 v2 && v2->scope == PendingScope;
1222 if (v2->type == Tlabel) {
1223 v2->scope = CondScope;
1225 v2->scope = OutScope;
1228 case OutScope: break;
1237 The value of a variable is store separately from the variable, on an
1238 analogue of a stack frame. There are (currently) two frames that can be
1239 active. A global frame which currently only stores constants, and a
1240 stacked frame which stores local variables. Each variable knows if it
1241 is global or not, and what its index into the frame is.
1243 Values in the global frame are known immediately they are relevant, so
1244 the frame needs to be reallocated as it grows so it can store those
1245 values. The local frame doesn't get values until the interpreted phase
1246 is started, so there is no need to allocate until the size is known.
1248 ###### variable fields
1252 ###### parse context
1254 short global_size, global_alloc;
1256 void *global, *local;
1258 ###### ast functions
1260 static struct value *var_value(struct parse_context *c, struct variable *v)
1263 if (!c->local || !v->type)
1265 if (v->frame_pos + v->type->size > c->local_size) {
1266 printf("INVALID frame_pos\n"); // NOTEST
1269 return c->local + v->frame_pos;
1271 if (c->global_size > c->global_alloc) {
1272 int old = c->global_alloc;
1273 c->global_alloc = (c->global_size | 1023) + 1024;
1274 c->global = realloc(c->global, c->global_alloc);
1275 memset(c->global + old, 0, c->global_alloc - old);
1277 return c->global + v->frame_pos;
1280 static struct value *global_alloc(struct parse_context *c, struct type *t,
1281 struct variable *v, struct value *init)
1284 struct variable scratch;
1286 if (t->prepare_type)
1287 t->prepare_type(c, t, 1); // NOTEST
1289 if (c->global_size & (t->align - 1))
1290 c->global_size = (c->global_size + t->align) & ~(t->align-1); // UNTESTED
1295 v->frame_pos = c->global_size;
1297 c->global_size += v->type->size;
1298 ret = var_value(c, v);
1300 memcpy(ret, init, t->size);
1306 As global values are found -- struct field initializers, labels etc --
1307 `global_alloc()` is called to record the value in the global frame.
1309 When the program is fully parsed, we need to walk the list of variables
1310 to find any that weren't merged away and that aren't global, and to
1311 calculate the frame size and assign a frame position for each variable.
1312 For this we have `scope_finalize()`.
1314 ###### ast functions
1316 static void scope_finalize(struct parse_context *c)
1320 for (b = c->varlist; b; b = b->next) {
1322 for (v = b->var; v; v = v->previous) {
1323 struct type *t = v->type;
1328 if (c->local_size & (t->align - 1))
1329 c->local_size = (c->local_size + t->align) & ~(t->align-1);
1330 v->frame_pos = c->local_size;
1331 c->local_size += v->type->size;
1334 c->local = calloc(1, c->local_size);
1337 ###### free context storage
1338 free(context.global);
1339 free(context.local);
1343 Executables can be lots of different things. In many cases an
1344 executable is just an operation combined with one or two other
1345 executables. This allows for expressions and lists etc. Other times an
1346 executable is something quite specific like a constant or variable name.
1347 So we define a `struct exec` to be a general executable with a type, and
1348 a `struct binode` which is a subclass of `exec`, forms a node in a
1349 binary tree, and holds an operation. There will be other subclasses,
1350 and to access these we need to be able to `cast` the `exec` into the
1351 various other types. The first field in any `struct exec` is the type
1352 from the `exec_types` enum.
1355 #define cast(structname, pointer) ({ \
1356 const typeof( ((struct structname *)0)->type) *__mptr = &(pointer)->type; \
1357 if (__mptr && *__mptr != X##structname) abort(); \
1358 (struct structname *)( (char *)__mptr);})
1360 #define new(structname) ({ \
1361 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1362 __ptr->type = X##structname; \
1363 __ptr->line = -1; __ptr->column = -1; \
1366 #define new_pos(structname, token) ({ \
1367 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1368 __ptr->type = X##structname; \
1369 __ptr->line = token.line; __ptr->column = token.col; \
1378 enum exec_types type;
1386 struct exec *left, *right;
1389 ###### ast functions
1391 static int __fput_loc(struct exec *loc, FILE *f)
1395 if (loc->line >= 0) {
1396 fprintf(f, "%d:%d: ", loc->line, loc->column);
1399 if (loc->type == Xbinode)
1400 return __fput_loc(cast(binode,loc)->left, f) ||
1401 __fput_loc(cast(binode,loc)->right, f); // NOTEST
1404 static void fput_loc(struct exec *loc, FILE *f)
1406 if (!__fput_loc(loc, f))
1407 fprintf(f, "??:??: "); // NOTEST
1410 Each different type of `exec` node needs a number of functions defined,
1411 a bit like methods. We must be able to free it, print it, analyse it
1412 and execute it. Once we have specific `exec` types we will need to
1413 parse them too. Let's take this a bit more slowly.
1417 The parser generator requires a `free_foo` function for each struct
1418 that stores attributes and they will often be `exec`s and subtypes
1419 there-of. So we need `free_exec` which can handle all the subtypes,
1420 and we need `free_binode`.
1422 ###### ast functions
1424 static void free_binode(struct binode *b)
1429 free_exec(b->right);
1433 ###### core functions
1434 static void free_exec(struct exec *e)
1443 ###### forward decls
1445 static void free_exec(struct exec *e);
1447 ###### free exec cases
1448 case Xbinode: free_binode(cast(binode, e)); break;
1452 Printing an `exec` requires that we know the current indent level for
1453 printing line-oriented components. As will become clear later, we
1454 also want to know what sort of bracketing to use.
1456 ###### ast functions
1458 static void do_indent(int i, char *str)
1465 ###### core functions
1466 static void print_binode(struct binode *b, int indent, int bracket)
1470 ## print binode cases
1474 static void print_exec(struct exec *e, int indent, int bracket)
1480 print_binode(cast(binode, e), indent, bracket); break;
1485 ###### forward decls
1487 static void print_exec(struct exec *e, int indent, int bracket);
1491 As discussed, analysis involves propagating type requirements around the
1492 program and looking for errors.
1494 So `propagate_types` is passed an expected type (being a `struct type`
1495 pointer together with some `val_rules` flags) that the `exec` is
1496 expected to return, and returns the type that it does return, either
1497 of which can be `NULL` signifying "unknown". An `ok` flag is passed
1498 by reference. It is set to `0` when an error is found, and `2` when
1499 any change is made. If it remains unchanged at `1`, then no more
1500 propagation is needed.
1504 enum val_rules {Rnolabel = 1<<0, Rboolok = 1<<1, Rnoconstant = 2<<1};
1508 if (rules & Rnolabel)
1509 fputs(" (labels not permitted)", stderr);
1512 ###### core functions
1514 static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1515 struct type *type, int rules);
1516 static struct type *__propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1517 struct type *type, int rules)
1524 switch (prog->type) {
1527 struct binode *b = cast(binode, prog);
1529 ## propagate binode cases
1533 ## propagate exec cases
1538 static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1539 struct type *type, int rules)
1541 struct type *ret = __propagate_types(prog, c, ok, type, rules);
1550 Interpreting an `exec` doesn't require anything but the `exec`. State
1551 is stored in variables and each variable will be directly linked from
1552 within the `exec` tree. The exception to this is the `main` function
1553 which needs to look at command line arguments. This function will be
1554 interpreted separately.
1556 Each `exec` can return a value combined with a type in `struct lrval`.
1557 The type may be `Tnone` but must be non-NULL. Some `exec`s will return
1558 the location of a value, which can be updated, in `lval`. Others will
1559 set `lval` to NULL indicating that there is a value of appropriate type
1562 ###### core functions
1566 struct value rval, *lval;
1569 static struct lrval _interp_exec(struct parse_context *c, struct exec *e);
1571 static struct value interp_exec(struct parse_context *c, struct exec *e,
1572 struct type **typeret)
1574 struct lrval ret = _interp_exec(c, e);
1576 if (!ret.type) abort();
1578 *typeret = ret.type;
1580 dup_value(ret.type, ret.lval, &ret.rval);
1584 static struct value *linterp_exec(struct parse_context *c, struct exec *e,
1585 struct type **typeret)
1587 struct lrval ret = _interp_exec(c, e);
1590 *typeret = ret.type;
1592 free_value(ret.type, &ret.rval);
1596 static struct lrval _interp_exec(struct parse_context *c, struct exec *e)
1599 struct value rv = {}, *lrv = NULL;
1600 struct type *rvtype;
1602 rvtype = ret.type = Tnone;
1612 struct binode *b = cast(binode, e);
1613 struct value left, right, *lleft;
1614 struct type *ltype, *rtype;
1615 ltype = rtype = Tnone;
1617 ## interp binode cases
1619 free_value(ltype, &left);
1620 free_value(rtype, &right);
1623 ## interp exec cases
1633 Now that we have the shape of the interpreter in place we can add some
1634 complex types and connected them in to the data structures and the
1635 different phases of parse, analyse, print, interpret.
1637 Thus far we have arrays and structs.
1641 Arrays can be declared by giving a size and a type, as `[size]type' so
1642 `freq:[26]number` declares `freq` to be an array of 26 numbers. The
1643 size can be either a literal number, or a named constant. Some day an
1644 arbitrary expression will be supported.
1646 As a formal parameter to a function, the array can be declared with a
1647 new variable as the size: `name:[size::number]string`. The `size`
1648 variable is set to the size of the array and must be a constant. As
1649 `number` is the only supported type, it can be left out:
1650 `name:[size::]string`.
1652 Arrays cannot be assigned. When pointers are introduced we will also
1653 introduce array slices which can refer to part or all of an array -
1654 the assignment syntax will create a slice. For now, an array can only
1655 ever be referenced by the name it is declared with. It is likely that
1656 a "`copy`" primitive will eventually be define which can be used to
1657 make a copy of an array with controllable recursive depth.
1659 For now we have two sorts of array, those with fixed size either because
1660 it is given as a literal number or because it is a struct member (which
1661 cannot have a runtime-changing size), and those with a size that is
1662 determined at runtime - local variables with a const size. The former
1663 have their size calculated at parse time, the latter at run time.
1665 For the latter type, the `size` field of the type is the size of a
1666 pointer, and the array is reallocated every time it comes into scope.
1668 We differentiate struct fields with a const size from local variables
1669 with a const size by whether they are prepared at parse time or not.
1671 ###### type union fields
1674 int unspec; // size is unspecified - vsize must be set.
1677 struct variable *vsize;
1678 struct type *member;
1681 ###### value union fields
1682 void *array; // used if not static_size
1684 ###### value functions
1686 static void array_prepare_type(struct parse_context *c, struct type *type,
1689 struct value *vsize;
1691 if (!type->array.vsize || type->array.static_size)
1694 vsize = var_value(c, type->array.vsize);
1696 mpz_tdiv_q(q, mpq_numref(vsize->num), mpq_denref(vsize->num));
1697 type->array.size = mpz_get_si(q);
1701 type->array.static_size = 1;
1702 type->size = type->array.size * type->array.member->size;
1703 type->align = type->array.member->align;
1707 static void array_init(struct type *type, struct value *val)
1710 void *ptr = val->ptr;
1714 if (!type->array.static_size) {
1715 val->array = calloc(type->array.size,
1716 type->array.member->size);
1719 for (i = 0; i < type->array.size; i++) {
1721 v = (void*)ptr + i * type->array.member->size;
1722 val_init(type->array.member, v);
1726 static void array_free(struct type *type, struct value *val)
1729 void *ptr = val->ptr;
1731 if (!type->array.static_size)
1733 for (i = 0; i < type->array.size; i++) {
1735 v = (void*)ptr + i * type->array.member->size;
1736 free_value(type->array.member, v);
1738 if (!type->array.static_size)
1742 static int array_compat(struct type *require, struct type *have)
1744 if (have->compat != require->compat)
1745 return 0; // UNTESTED
1746 /* Both are arrays, so we can look at details */
1747 if (!type_compat(require->array.member, have->array.member, 0))
1749 if (have->array.unspec && require->array.unspec) {
1750 if (have->array.vsize && require->array.vsize &&
1751 have->array.vsize != require->array.vsize) // UNTESTED
1752 /* sizes might not be the same */
1753 return 0; // UNTESTED
1756 if (have->array.unspec || require->array.unspec)
1757 return 1; // UNTESTED
1758 if (require->array.vsize == NULL && have->array.vsize == NULL)
1759 return require->array.size == have->array.size;
1761 return require->array.vsize == have->array.vsize; // UNTESTED
1764 static void array_print_type(struct type *type, FILE *f)
1767 if (type->array.vsize) {
1768 struct binding *b = type->array.vsize->name;
1769 fprintf(f, "%.*s%s]", b->name.len, b->name.txt,
1770 type->array.unspec ? "::" : "");
1772 fprintf(f, "%d]", type->array.size);
1773 type_print(type->array.member, f);
1776 static struct type array_prototype = {
1778 .prepare_type = array_prepare_type,
1779 .print_type = array_print_type,
1780 .compat = array_compat,
1782 .size = sizeof(void*),
1783 .align = sizeof(void*),
1786 ###### declare terminals
1791 | [ NUMBER ] Type ${ {
1794 struct text noname = { "", 0 };
1797 $0 = t = add_type(c, noname, &array_prototype);
1798 t->array.member = $<4;
1799 t->array.vsize = NULL;
1800 if (number_parse(num, tail, $2.txt) == 0)
1801 tok_err(c, "error: unrecognised number", &$2);
1803 tok_err(c, "error: unsupported number suffix", &$2);
1805 t->array.size = mpz_get_ui(mpq_numref(num));
1806 if (mpz_cmp_ui(mpq_denref(num), 1) != 0) {
1807 tok_err(c, "error: array size must be an integer",
1809 } else if (mpz_cmp_ui(mpq_numref(num), 1UL << 30) >= 0)
1810 tok_err(c, "error: array size is too large",
1814 t->array.static_size = 1;
1815 t->size = t->array.size * t->array.member->size;
1816 t->align = t->array.member->align;
1819 | [ IDENTIFIER ] Type ${ {
1820 struct variable *v = var_ref(c, $2.txt);
1821 struct text noname = { "", 0 };
1824 tok_err(c, "error: name undeclared", &$2);
1825 else if (!v->constant)
1826 tok_err(c, "error: array size must be a constant", &$2);
1828 $0 = add_type(c, noname, &array_prototype);
1829 $0->array.member = $<4;
1831 $0->array.vsize = v;
1836 OptType -> Type ${ $0 = $<1; }$
1839 ###### formal type grammar
1841 | [ IDENTIFIER :: OptType ] Type ${ {
1842 struct variable *v = var_decl(c, $ID.txt);
1843 struct text noname = { "", 0 };
1849 $0 = add_type(c, noname, &array_prototype);
1850 $0->array.member = $<6;
1852 $0->array.unspec = 1;
1853 $0->array.vsize = v;
1859 ###### variable grammar
1861 | Variable [ Expression ] ${ {
1862 struct binode *b = new(binode);
1869 ###### print binode cases
1871 print_exec(b->left, -1, bracket);
1873 print_exec(b->right, -1, bracket);
1877 ###### propagate binode cases
1879 /* left must be an array, right must be a number,
1880 * result is the member type of the array
1882 propagate_types(b->right, c, ok, Tnum, 0);
1883 t = propagate_types(b->left, c, ok, NULL, rules & Rnoconstant);
1884 if (!t || t->compat != array_compat) {
1885 type_err(c, "error: %1 cannot be indexed", prog, t, 0, NULL);
1888 if (!type_compat(type, t->array.member, rules)) {
1889 type_err(c, "error: have %1 but need %2", prog,
1890 t->array.member, rules, type);
1892 return t->array.member;
1896 ###### interp binode cases
1902 lleft = linterp_exec(c, b->left, <ype);
1903 right = interp_exec(c, b->right, &rtype);
1905 mpz_tdiv_q(q, mpq_numref(right.num), mpq_denref(right.num));
1909 if (ltype->array.static_size)
1912 ptr = *(void**)lleft;
1913 rvtype = ltype->array.member;
1914 if (i >= 0 && i < ltype->array.size)
1915 lrv = ptr + i * rvtype->size;
1917 val_init(ltype->array.member, &rv);
1924 A `struct` is a data-type that contains one or more other data-types.
1925 It differs from an array in that each member can be of a different
1926 type, and they are accessed by name rather than by number. Thus you
1927 cannot choose an element by calculation, you need to know what you
1930 The language makes no promises about how a given structure will be
1931 stored in memory - it is free to rearrange fields to suit whatever
1932 criteria seems important.
1934 Structs are declared separately from program code - they cannot be
1935 declared in-line in a variable declaration like arrays can. A struct
1936 is given a name and this name is used to identify the type - the name
1937 is not prefixed by the word `struct` as it would be in C.
1939 Structs are only treated as the same if they have the same name.
1940 Simply having the same fields in the same order is not enough. This
1941 might change once we can create structure initializers from a list of
1944 Each component datum is identified much like a variable is declared,
1945 with a name, one or two colons, and a type. The type cannot be omitted
1946 as there is no opportunity to deduce the type from usage. An initial
1947 value can be given following an equals sign, so
1949 ##### Example: a struct type
1955 would declare a type called "complex" which has two number fields,
1956 each initialised to zero.
1958 Struct will need to be declared separately from the code that uses
1959 them, so we will need to be able to print out the declaration of a
1960 struct when reprinting the whole program. So a `print_type_decl` type
1961 function will be needed.
1963 ###### type union fields
1975 ###### type functions
1976 void (*print_type_decl)(struct type *type, FILE *f);
1978 ###### value functions
1980 static void structure_init(struct type *type, struct value *val)
1984 for (i = 0; i < type->structure.nfields; i++) {
1986 v = (void*) val->ptr + type->structure.fields[i].offset;
1987 if (type->structure.fields[i].init)
1988 dup_value(type->structure.fields[i].type,
1989 type->structure.fields[i].init,
1992 val_init(type->structure.fields[i].type, v);
1996 static void structure_free(struct type *type, struct value *val)
2000 for (i = 0; i < type->structure.nfields; i++) {
2002 v = (void*)val->ptr + type->structure.fields[i].offset;
2003 free_value(type->structure.fields[i].type, v);
2007 static void structure_free_type(struct type *t)
2010 for (i = 0; i < t->structure.nfields; i++)
2011 if (t->structure.fields[i].init) {
2012 free_value(t->structure.fields[i].type,
2013 t->structure.fields[i].init);
2015 free(t->structure.fields);
2018 static struct type structure_prototype = {
2019 .init = structure_init,
2020 .free = structure_free,
2021 .free_type = structure_free_type,
2022 .print_type_decl = structure_print_type,
2036 ###### free exec cases
2038 free_exec(cast(fieldref, e)->left);
2042 ###### declare terminals
2045 ###### variable grammar
2047 | Variable . IDENTIFIER ${ {
2048 struct fieldref *fr = new_pos(fieldref, $2);
2055 ###### print exec cases
2059 struct fieldref *f = cast(fieldref, e);
2060 print_exec(f->left, -1, bracket);
2061 printf(".%.*s", f->name.len, f->name.txt);
2065 ###### ast functions
2066 static int find_struct_index(struct type *type, struct text field)
2069 for (i = 0; i < type->structure.nfields; i++)
2070 if (text_cmp(type->structure.fields[i].name, field) == 0)
2075 ###### propagate exec cases
2079 struct fieldref *f = cast(fieldref, prog);
2080 struct type *st = propagate_types(f->left, c, ok, NULL, 0);
2083 type_err(c, "error: unknown type for field access", f->left, // UNTESTED
2085 else if (st->init != structure_init)
2086 type_err(c, "error: field reference attempted on %1, not a struct",
2087 f->left, st, 0, NULL);
2088 else if (f->index == -2) {
2089 f->index = find_struct_index(st, f->name);
2091 type_err(c, "error: cannot find requested field in %1",
2092 f->left, st, 0, NULL);
2094 if (f->index >= 0) {
2095 struct type *ft = st->structure.fields[f->index].type;
2096 if (!type_compat(type, ft, rules))
2097 type_err(c, "error: have %1 but need %2", prog,
2104 ###### interp exec cases
2107 struct fieldref *f = cast(fieldref, e);
2109 struct value *lleft = linterp_exec(c, f->left, <ype);
2110 lrv = (void*)lleft->ptr + ltype->structure.fields[f->index].offset;
2111 rvtype = ltype->structure.fields[f->index].type;
2117 struct fieldlist *prev;
2121 ###### ast functions
2122 static void free_fieldlist(struct fieldlist *f)
2126 free_fieldlist(f->prev);
2128 free_value(f->f.type, f->f.init); // UNTESTED
2129 free(f->f.init); // UNTESTED
2134 ###### top level grammar
2135 DeclareStruct -> struct IDENTIFIER FieldBlock Newlines ${ {
2137 add_type(c, $2.txt, &structure_prototype);
2139 struct fieldlist *f;
2141 for (f = $3; f; f=f->prev)
2144 t->structure.nfields = cnt;
2145 t->structure.fields = calloc(cnt, sizeof(struct field));
2148 int a = f->f.type->align;
2150 t->structure.fields[cnt] = f->f;
2151 if (t->size & (a-1))
2152 t->size = (t->size | (a-1)) + 1;
2153 t->structure.fields[cnt].offset = t->size;
2154 t->size += ((f->f.type->size - 1) | (a-1)) + 1;
2163 FieldBlock -> { IN OptNL FieldLines OUT OptNL } ${ $0 = $<FL; }$
2164 | { SimpleFieldList } ${ $0 = $<SFL; }$
2165 | IN OptNL FieldLines OUT ${ $0 = $<FL; }$
2166 | SimpleFieldList EOL ${ $0 = $<SFL; }$
2168 FieldLines -> SimpleFieldList Newlines ${ $0 = $<SFL; }$
2169 | FieldLines SimpleFieldList Newlines ${
2174 SimpleFieldList -> Field ${ $0 = $<F; }$
2175 | SimpleFieldList ; Field ${
2179 | SimpleFieldList ; ${
2182 | ERROR ${ tok_err(c, "Syntax error in struct field", &$1); }$
2184 Field -> IDENTIFIER : Type = Expression ${ {
2187 $0 = calloc(1, sizeof(struct fieldlist));
2188 $0->f.name = $1.txt;
2193 propagate_types($<5, c, &ok, $3, 0);
2196 c->parse_error = 1; // UNTESTED
2198 struct value vl = interp_exec(c, $5, NULL);
2199 $0->f.init = global_alloc(c, $0->f.type, NULL, &vl);
2202 | IDENTIFIER : Type ${
2203 $0 = calloc(1, sizeof(struct fieldlist));
2204 $0->f.name = $1.txt;
2206 if ($0->f.type->prepare_type)
2207 $0->f.type->prepare_type(c, $0->f.type, 1);
2210 ###### forward decls
2211 static void structure_print_type(struct type *t, FILE *f);
2213 ###### value functions
2214 static void structure_print_type(struct type *t, FILE *f) // UNTESTED
2218 fprintf(f, "struct %.*s\n", t->name.len, t->name.txt);
2220 for (i = 0; i < t->structure.nfields; i++) {
2221 struct field *fl = t->structure.fields + i;
2222 fprintf(f, " %.*s : ", fl->name.len, fl->name.txt);
2223 type_print(fl->type, f);
2224 if (fl->type->print && fl->init) {
2226 if (fl->type == Tstr)
2227 fprintf(f, "\""); // UNTESTED
2228 print_value(fl->type, fl->init);
2229 if (fl->type == Tstr)
2230 fprintf(f, "\""); // UNTESTED
2236 ###### print type decls
2238 struct type *t; // UNTESTED
2241 while (target != 0) {
2243 for (t = context.typelist; t ; t=t->next)
2244 if (t->print_type_decl) {
2253 t->print_type_decl(t, stdout);
2261 A function is a named chunk of code which can be passed parameters and
2262 can return results. Each function has an implicit type which includes
2263 the set of parameters and the return value. As yet these types cannot
2264 be declared separate from the function itself.
2266 In fact, only one function is currently possible - `main`. `main` is
2267 passed an array of strings together with the size of the array, and
2268 doesn't return anything. The strings are command line arguments.
2270 The parameters can be specified either in parentheses as a list, such as
2272 ##### Example: function 1
2274 func main(av:[ac::number]string)
2277 or as an indented list of one parameter per line
2279 ##### Example: function 2
2282 argv:[argc::number]string
2294 MainFunction -> func main ( OpenScope Args ) Block Newlines ${
2297 $0->left = reorder_bilist($<Ar);
2299 var_block_close(c, CloseSequential);
2300 if (c->scope_stack && !c->parse_error) abort();
2302 | func main IN OpenScope OptNL Args OUT OptNL do Block Newlines ${
2305 $0->left = reorder_bilist($<Ar);
2307 var_block_close(c, CloseSequential);
2308 if (c->scope_stack && !c->parse_error) abort();
2310 | func main NEWLINE OpenScope OptNL do Block Newlines ${
2315 var_block_close(c, CloseSequential);
2316 if (c->scope_stack && !c->parse_error) abort();
2319 Args -> ${ $0 = NULL; }$
2320 | Varlist ${ $0 = $<1; }$
2321 | Varlist ; ${ $0 = $<1; }$
2322 | Varlist NEWLINE ${ $0 = $<1; }$
2324 Varlist -> Varlist ; ArgDecl ${ // UNTESTED
2338 ArgDecl -> IDENTIFIER : FormalType ${ {
2339 struct variable *v = var_decl(c, $1.txt);
2345 ## Executables: the elements of code
2347 Each code element needs to be parsed, printed, analysed,
2348 interpreted, and freed. There are several, so let's just start with
2349 the easy ones and work our way up.
2353 We have already met values as separate objects. When manifest
2354 constants appear in the program text, that must result in an executable
2355 which has a constant value. So the `val` structure embeds a value in
2368 ###### ast functions
2369 struct val *new_val(struct type *T, struct token tk)
2371 struct val *v = new_pos(val, tk);
2382 $0 = new_val(Tbool, $1);
2386 $0 = new_val(Tbool, $1);
2390 $0 = new_val(Tnum, $1);
2393 if (number_parse($0->val.num, tail, $1.txt) == 0)
2394 mpq_init($0->val.num); // UNTESTED
2396 tok_err(c, "error: unsupported number suffix",
2401 $0 = new_val(Tstr, $1);
2404 string_parse(&$1, '\\', &$0->val.str, tail);
2406 tok_err(c, "error: unsupported string suffix",
2411 $0 = new_val(Tstr, $1);
2414 string_parse(&$1, '\\', &$0->val.str, tail);
2416 tok_err(c, "error: unsupported string suffix",
2421 ###### print exec cases
2424 struct val *v = cast(val, e);
2425 if (v->vtype == Tstr)
2427 print_value(v->vtype, &v->val);
2428 if (v->vtype == Tstr)
2433 ###### propagate exec cases
2436 struct val *val = cast(val, prog);
2437 if (!type_compat(type, val->vtype, rules))
2438 type_err(c, "error: expected %1%r found %2",
2439 prog, type, rules, val->vtype);
2443 ###### interp exec cases
2445 rvtype = cast(val, e)->vtype;
2446 dup_value(rvtype, &cast(val, e)->val, &rv);
2449 ###### ast functions
2450 static void free_val(struct val *v)
2453 free_value(v->vtype, &v->val);
2457 ###### free exec cases
2458 case Xval: free_val(cast(val, e)); break;
2460 ###### ast functions
2461 // Move all nodes from 'b' to 'rv', reversing their order.
2462 // In 'b' 'left' is a list, and 'right' is the last node.
2463 // In 'rv', left' is the first node and 'right' is a list.
2464 static struct binode *reorder_bilist(struct binode *b)
2466 struct binode *rv = NULL;
2469 struct exec *t = b->right;
2473 b = cast(binode, b->left);
2483 Just as we used a `val` to wrap a value into an `exec`, we similarly
2484 need a `var` to wrap a `variable` into an exec. While each `val`
2485 contained a copy of the value, each `var` holds a link to the variable
2486 because it really is the same variable no matter where it appears.
2487 When a variable is used, we need to remember to follow the `->merged`
2488 link to find the primary instance.
2496 struct variable *var;
2504 VariableDecl -> IDENTIFIER : ${ {
2505 struct variable *v = var_decl(c, $1.txt);
2506 $0 = new_pos(var, $1);
2511 v = var_ref(c, $1.txt);
2513 type_err(c, "error: variable '%v' redeclared",
2515 type_err(c, "info: this is where '%v' was first declared",
2516 v->where_decl, NULL, 0, NULL);
2519 | IDENTIFIER :: ${ {
2520 struct variable *v = var_decl(c, $1.txt);
2521 $0 = new_pos(var, $1);
2527 v = var_ref(c, $1.txt);
2529 type_err(c, "error: variable '%v' redeclared",
2531 type_err(c, "info: this is where '%v' was first declared",
2532 v->where_decl, NULL, 0, NULL);
2535 | IDENTIFIER : Type ${ {
2536 struct variable *v = var_decl(c, $1.txt);
2537 $0 = new_pos(var, $1);
2544 v = var_ref(c, $1.txt);
2546 type_err(c, "error: variable '%v' redeclared",
2548 type_err(c, "info: this is where '%v' was first declared",
2549 v->where_decl, NULL, 0, NULL);
2552 | IDENTIFIER :: Type ${ {
2553 struct variable *v = var_decl(c, $1.txt);
2554 $0 = new_pos(var, $1);
2562 v = var_ref(c, $1.txt);
2564 type_err(c, "error: variable '%v' redeclared",
2566 type_err(c, "info: this is where '%v' was first declared",
2567 v->where_decl, NULL, 0, NULL);
2572 Variable -> IDENTIFIER ${ {
2573 struct variable *v = var_ref(c, $1.txt);
2574 $0 = new_pos(var, $1);
2576 /* This might be a label - allocate a var just in case */
2577 v = var_decl(c, $1.txt);
2584 cast(var, $0)->var = v;
2588 ###### print exec cases
2591 struct var *v = cast(var, e);
2593 struct binding *b = v->var->name;
2594 printf("%.*s", b->name.len, b->name.txt);
2601 if (loc && loc->type == Xvar) {
2602 struct var *v = cast(var, loc);
2604 struct binding *b = v->var->name;
2605 fprintf(stderr, "%.*s", b->name.len, b->name.txt);
2607 fputs("???", stderr); // NOTEST
2609 fputs("NOTVAR", stderr); // NOTEST
2612 ###### propagate exec cases
2616 struct var *var = cast(var, prog);
2617 struct variable *v = var->var;
2619 type_err(c, "%d:BUG: no variable!!", prog, NULL, 0, NULL); // NOTEST
2620 return Tnone; // NOTEST
2623 if (v->constant && (rules & Rnoconstant)) {
2624 type_err(c, "error: Cannot assign to a constant: %v",
2625 prog, NULL, 0, NULL);
2626 type_err(c, "info: name was defined as a constant here",
2627 v->where_decl, NULL, 0, NULL);
2630 if (v->type == Tnone && v->where_decl == prog)
2631 type_err(c, "error: variable used but not declared: %v",
2632 prog, NULL, 0, NULL);
2633 if (v->type == NULL) {
2634 if (type && *ok != 0) {
2636 v->where_set = prog;
2641 if (!type_compat(type, v->type, rules)) {
2642 type_err(c, "error: expected %1%r but variable '%v' is %2", prog,
2643 type, rules, v->type);
2644 type_err(c, "info: this is where '%v' was set to %1", v->where_set,
2645 v->type, rules, NULL);
2652 ###### interp exec cases
2655 struct var *var = cast(var, e);
2656 struct variable *v = var->var;
2659 lrv = var_value(c, v);
2664 ###### ast functions
2666 static void free_var(struct var *v)
2671 ###### free exec cases
2672 case Xvar: free_var(cast(var, e)); break;
2674 ### Expressions: Conditional
2676 Our first user of the `binode` will be conditional expressions, which
2677 is a bit odd as they actually have three components. That will be
2678 handled by having 2 binodes for each expression. The conditional
2679 expression is the lowest precedence operator which is why we define it
2680 first - to start the precedence list.
2682 Conditional expressions are of the form "value `if` condition `else`
2683 other_value". They associate to the right, so everything to the right
2684 of `else` is part of an else value, while only a higher-precedence to
2685 the left of `if` is the if values. Between `if` and `else` there is no
2686 room for ambiguity, so a full conditional expression is allowed in
2698 Expression -> Expression if Expression else Expression $$ifelse ${ {
2699 struct binode *b1 = new(binode);
2700 struct binode *b2 = new(binode);
2709 ## expression grammar
2711 ###### print binode cases
2714 b2 = cast(binode, b->right);
2715 if (bracket) printf("(");
2716 print_exec(b2->left, -1, bracket);
2718 print_exec(b->left, -1, bracket);
2720 print_exec(b2->right, -1, bracket);
2721 if (bracket) printf(")");
2724 ###### propagate binode cases
2727 /* cond must be Tbool, others must match */
2728 struct binode *b2 = cast(binode, b->right);
2731 propagate_types(b->left, c, ok, Tbool, 0);
2732 t = propagate_types(b2->left, c, ok, type, Rnolabel);
2733 t2 = propagate_types(b2->right, c, ok, type ?: t, Rnolabel);
2737 ###### interp binode cases
2740 struct binode *b2 = cast(binode, b->right);
2741 left = interp_exec(c, b->left, <ype);
2743 rv = interp_exec(c, b2->left, &rvtype); // UNTESTED
2745 rv = interp_exec(c, b2->right, &rvtype);
2749 ### Expressions: Boolean
2751 The next class of expressions to use the `binode` will be Boolean
2752 expressions. "`and then`" and "`or else`" are similar to `and` and `or`
2753 have same corresponding precendence. The difference is that they don't
2754 evaluate the second expression if not necessary.
2763 ###### expr precedence
2768 ###### expression grammar
2769 | Expression or Expression ${ {
2770 struct binode *b = new(binode);
2776 | Expression or else Expression ${ {
2777 struct binode *b = new(binode);
2784 | Expression and Expression ${ {
2785 struct binode *b = new(binode);
2791 | Expression and then Expression ${ {
2792 struct binode *b = new(binode);
2799 | not Expression ${ {
2800 struct binode *b = new(binode);
2806 ###### print binode cases
2808 if (bracket) printf("(");
2809 print_exec(b->left, -1, bracket);
2811 print_exec(b->right, -1, bracket);
2812 if (bracket) printf(")");
2815 if (bracket) printf("(");
2816 print_exec(b->left, -1, bracket);
2817 printf(" and then ");
2818 print_exec(b->right, -1, bracket);
2819 if (bracket) printf(")");
2822 if (bracket) printf("(");
2823 print_exec(b->left, -1, bracket);
2825 print_exec(b->right, -1, bracket);
2826 if (bracket) printf(")");
2829 if (bracket) printf("(");
2830 print_exec(b->left, -1, bracket);
2831 printf(" or else ");
2832 print_exec(b->right, -1, bracket);
2833 if (bracket) printf(")");
2836 if (bracket) printf("(");
2838 print_exec(b->right, -1, bracket);
2839 if (bracket) printf(")");
2842 ###### propagate binode cases
2848 /* both must be Tbool, result is Tbool */
2849 propagate_types(b->left, c, ok, Tbool, 0);
2850 propagate_types(b->right, c, ok, Tbool, 0);
2851 if (type && type != Tbool)
2852 type_err(c, "error: %1 operation found where %2 expected", prog,
2856 ###### interp binode cases
2858 rv = interp_exec(c, b->left, &rvtype);
2859 right = interp_exec(c, b->right, &rtype);
2860 rv.bool = rv.bool && right.bool;
2863 rv = interp_exec(c, b->left, &rvtype);
2865 rv = interp_exec(c, b->right, NULL);
2868 rv = interp_exec(c, b->left, &rvtype);
2869 right = interp_exec(c, b->right, &rtype);
2870 rv.bool = rv.bool || right.bool;
2873 rv = interp_exec(c, b->left, &rvtype);
2875 rv = interp_exec(c, b->right, NULL);
2878 rv = interp_exec(c, b->right, &rvtype);
2882 ### Expressions: Comparison
2884 Of slightly higher precedence that Boolean expressions are Comparisons.
2885 A comparison takes arguments of any comparable type, but the two types
2888 To simplify the parsing we introduce an `eop` which can record an
2889 expression operator, and the `CMPop` non-terminal will match one of them.
2896 ###### ast functions
2897 static void free_eop(struct eop *e)
2911 ###### expr precedence
2912 $LEFT < > <= >= == != CMPop
2914 ###### expression grammar
2915 | Expression CMPop Expression ${ {
2916 struct binode *b = new(binode);
2926 CMPop -> < ${ $0.op = Less; }$
2927 | > ${ $0.op = Gtr; }$
2928 | <= ${ $0.op = LessEq; }$
2929 | >= ${ $0.op = GtrEq; }$
2930 | == ${ $0.op = Eql; }$
2931 | != ${ $0.op = NEql; }$
2933 ###### print binode cases
2941 if (bracket) printf("(");
2942 print_exec(b->left, -1, bracket);
2944 case Less: printf(" < "); break;
2945 case LessEq: printf(" <= "); break;
2946 case Gtr: printf(" > "); break;
2947 case GtrEq: printf(" >= "); break;
2948 case Eql: printf(" == "); break;
2949 case NEql: printf(" != "); break;
2950 default: abort(); // NOTEST
2952 print_exec(b->right, -1, bracket);
2953 if (bracket) printf(")");
2956 ###### propagate binode cases
2963 /* Both must match but not be labels, result is Tbool */
2964 t = propagate_types(b->left, c, ok, NULL, Rnolabel);
2966 propagate_types(b->right, c, ok, t, 0);
2968 t = propagate_types(b->right, c, ok, NULL, Rnolabel); // UNTESTED
2970 t = propagate_types(b->left, c, ok, t, 0); // UNTESTED
2972 if (!type_compat(type, Tbool, 0))
2973 type_err(c, "error: Comparison returns %1 but %2 expected", prog,
2974 Tbool, rules, type);
2977 ###### interp binode cases
2986 left = interp_exec(c, b->left, <ype);
2987 right = interp_exec(c, b->right, &rtype);
2988 cmp = value_cmp(ltype, rtype, &left, &right);
2991 case Less: rv.bool = cmp < 0; break;
2992 case LessEq: rv.bool = cmp <= 0; break;
2993 case Gtr: rv.bool = cmp > 0; break;
2994 case GtrEq: rv.bool = cmp >= 0; break;
2995 case Eql: rv.bool = cmp == 0; break;
2996 case NEql: rv.bool = cmp != 0; break;
2997 default: rv.bool = 0; break; // NOTEST
3002 ### Expressions: The rest
3004 The remaining expressions with the highest precedence are arithmetic,
3005 string concatenation, and string conversion. String concatenation
3006 (`++`) has the same precedence as multiplication and division, but lower
3009 String conversion is a temporary feature until I get a better type
3010 system. `$` is a prefix operator which expects a string and returns
3013 `+` and `-` are both infix and prefix operations (where they are
3014 absolute value and negation). These have different operator names.
3016 We also have a 'Bracket' operator which records where parentheses were
3017 found. This makes it easy to reproduce these when printing. Possibly I
3018 should only insert brackets were needed for precedence.
3028 ###### expr precedence
3034 ###### expression grammar
3035 | Expression Eop Expression ${ {
3036 struct binode *b = new(binode);
3043 | Expression Top Expression ${ {
3044 struct binode *b = new(binode);
3051 | ( Expression ) ${ {
3052 struct binode *b = new_pos(binode, $1);
3057 | Uop Expression ${ {
3058 struct binode *b = new(binode);
3063 | Value ${ $0 = $<1; }$
3064 | Variable ${ $0 = $<1; }$
3067 Eop -> + ${ $0.op = Plus; }$
3068 | - ${ $0.op = Minus; }$
3070 Uop -> + ${ $0.op = Absolute; }$
3071 | - ${ $0.op = Negate; }$
3072 | $ ${ $0.op = StringConv; }$
3074 Top -> * ${ $0.op = Times; }$
3075 | / ${ $0.op = Divide; }$
3076 | % ${ $0.op = Rem; }$
3077 | ++ ${ $0.op = Concat; }$
3079 ###### print binode cases
3086 if (bracket) printf("(");
3087 print_exec(b->left, indent, bracket);
3089 case Plus: fputs(" + ", stdout); break;
3090 case Minus: fputs(" - ", stdout); break;
3091 case Times: fputs(" * ", stdout); break;
3092 case Divide: fputs(" / ", stdout); break;
3093 case Rem: fputs(" % ", stdout); break;
3094 case Concat: fputs(" ++ ", stdout); break;
3095 default: abort(); // NOTEST
3097 print_exec(b->right, indent, bracket);
3098 if (bracket) printf(")");
3103 if (bracket) printf("(");
3105 case Absolute: fputs("+", stdout); break;
3106 case Negate: fputs("-", stdout); break;
3107 case StringConv: fputs("$", stdout); break;
3108 default: abort(); // NOTEST
3110 print_exec(b->right, indent, bracket);
3111 if (bracket) printf(")");
3115 print_exec(b->right, indent, bracket);
3119 ###### propagate binode cases
3125 /* both must be numbers, result is Tnum */
3128 /* as propagate_types ignores a NULL,
3129 * unary ops fit here too */
3130 propagate_types(b->left, c, ok, Tnum, 0);
3131 propagate_types(b->right, c, ok, Tnum, 0);
3132 if (!type_compat(type, Tnum, 0))
3133 type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
3138 /* both must be Tstr, result is Tstr */
3139 propagate_types(b->left, c, ok, Tstr, 0);
3140 propagate_types(b->right, c, ok, Tstr, 0);
3141 if (!type_compat(type, Tstr, 0))
3142 type_err(c, "error: Concat returns %1 but %2 expected", prog,
3147 /* op must be string, result is number */
3148 propagate_types(b->left, c, ok, Tstr, 0);
3149 if (!type_compat(type, Tnum, 0))
3150 type_err(c, // UNTESTED
3151 "error: Can only convert string to number, not %1",
3152 prog, type, 0, NULL);
3156 return propagate_types(b->right, c, ok, type, 0);
3158 ###### interp binode cases
3161 rv = interp_exec(c, b->left, &rvtype);
3162 right = interp_exec(c, b->right, &rtype);
3163 mpq_add(rv.num, rv.num, right.num);
3166 rv = interp_exec(c, b->left, &rvtype);
3167 right = interp_exec(c, b->right, &rtype);
3168 mpq_sub(rv.num, rv.num, right.num);
3171 rv = interp_exec(c, b->left, &rvtype);
3172 right = interp_exec(c, b->right, &rtype);
3173 mpq_mul(rv.num, rv.num, right.num);
3176 rv = interp_exec(c, b->left, &rvtype);
3177 right = interp_exec(c, b->right, &rtype);
3178 mpq_div(rv.num, rv.num, right.num);
3183 left = interp_exec(c, b->left, <ype);
3184 right = interp_exec(c, b->right, &rtype);
3185 mpz_init(l); mpz_init(r); mpz_init(rem);
3186 mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
3187 mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
3188 mpz_tdiv_r(rem, l, r);
3189 val_init(Tnum, &rv);
3190 mpq_set_z(rv.num, rem);
3191 mpz_clear(r); mpz_clear(l); mpz_clear(rem);
3196 rv = interp_exec(c, b->right, &rvtype);
3197 mpq_neg(rv.num, rv.num);
3200 rv = interp_exec(c, b->right, &rvtype);
3201 mpq_abs(rv.num, rv.num);
3204 rv = interp_exec(c, b->right, &rvtype);
3207 left = interp_exec(c, b->left, <ype);
3208 right = interp_exec(c, b->right, &rtype);
3210 rv.str = text_join(left.str, right.str);
3213 right = interp_exec(c, b->right, &rvtype);
3217 struct text tx = right.str;
3220 if (tx.txt[0] == '-') {
3221 neg = 1; // UNTESTED
3222 tx.txt++; // UNTESTED
3223 tx.len--; // UNTESTED
3225 if (number_parse(rv.num, tail, tx) == 0)
3226 mpq_init(rv.num); // UNTESTED
3228 mpq_neg(rv.num, rv.num); // UNTESTED
3230 printf("Unsupported suffix: %.*s\n", tx.len, tx.txt); // UNTESTED
3234 ###### value functions
3236 static struct text text_join(struct text a, struct text b)
3239 rv.len = a.len + b.len;
3240 rv.txt = malloc(rv.len);
3241 memcpy(rv.txt, a.txt, a.len);
3242 memcpy(rv.txt+a.len, b.txt, b.len);
3246 ### Blocks, Statements, and Statement lists.
3248 Now that we have expressions out of the way we need to turn to
3249 statements. There are simple statements and more complex statements.
3250 Simple statements do not contain (syntactic) newlines, complex statements do.
3252 Statements often come in sequences and we have corresponding simple
3253 statement lists and complex statement lists.
3254 The former comprise only simple statements separated by semicolons.
3255 The later comprise complex statements and simple statement lists. They are
3256 separated by newlines. Thus the semicolon is only used to separate
3257 simple statements on the one line. This may be overly restrictive,
3258 but I'm not sure I ever want a complex statement to share a line with
3261 Note that a simple statement list can still use multiple lines if
3262 subsequent lines are indented, so
3264 ###### Example: wrapped simple statement list
3269 is a single simple statement list. This might allow room for
3270 confusion, so I'm not set on it yet.
3272 A simple statement list needs no extra syntax. A complex statement
3273 list has two syntactic forms. It can be enclosed in braces (much like
3274 C blocks), or it can be introduced by an indent and continue until an
3275 unindented newline (much like Python blocks). With this extra syntax
3276 it is referred to as a block.
3278 Note that a block does not have to include any newlines if it only
3279 contains simple statements. So both of:
3281 if condition: a=b; d=f
3283 if condition { a=b; print f }
3287 In either case the list is constructed from a `binode` list with
3288 `Block` as the operator. When parsing the list it is most convenient
3289 to append to the end, so a list is a list and a statement. When using
3290 the list it is more convenient to consider a list to be a statement
3291 and a list. So we need a function to re-order a list.
3292 `reorder_bilist` serves this purpose.
3294 The only stand-alone statement we introduce at this stage is `pass`
3295 which does nothing and is represented as a `NULL` pointer in a `Block`
3296 list. Other stand-alone statements will follow once the infrastructure
3307 Block -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3308 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3309 | SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3310 | SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3311 | IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3313 OpenBlock -> OpenScope { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3314 | OpenScope { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3315 | OpenScope SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3316 | OpenScope SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3317 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3319 UseBlock -> { OpenScope IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3320 | { OpenScope SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3321 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3323 ColonBlock -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3324 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3325 | : SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3326 | : SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3327 | : IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3329 Statementlist -> ComplexStatements ${ $0 = reorder_bilist($<CS); }$
3331 ComplexStatements -> ComplexStatements ComplexStatement ${
3341 | ComplexStatement ${
3353 ComplexStatement -> SimpleStatements Newlines ${
3354 $0 = reorder_bilist($<SS);
3356 | SimpleStatements ; Newlines ${
3357 $0 = reorder_bilist($<SS);
3359 ## ComplexStatement Grammar
3362 SimpleStatements -> SimpleStatements ; SimpleStatement ${
3368 | SimpleStatement ${
3376 SimpleStatement -> pass ${ $0 = NULL; }$
3377 | ERROR ${ tok_err(c, "Syntax error in statement", &$1); }$
3378 ## SimpleStatement Grammar
3380 ###### print binode cases
3384 if (b->left == NULL) // UNTESTED
3385 printf("pass"); // UNTESTED
3387 print_exec(b->left, indent, bracket); // UNTESTED
3388 if (b->right) { // UNTESTED
3389 printf("; "); // UNTESTED
3390 print_exec(b->right, indent, bracket); // UNTESTED
3393 // block, one per line
3394 if (b->left == NULL)
3395 do_indent(indent, "pass\n");
3397 print_exec(b->left, indent, bracket);
3399 print_exec(b->right, indent, bracket);
3403 ###### propagate binode cases
3406 /* If any statement returns something other than Tnone
3407 * or Tbool then all such must return same type.
3408 * As each statement may be Tnone or something else,
3409 * we must always pass NULL (unknown) down, otherwise an incorrect
3410 * error might occur. We never return Tnone unless it is
3415 for (e = b; e; e = cast(binode, e->right)) {
3416 t = propagate_types(e->left, c, ok, NULL, rules);
3417 if ((rules & Rboolok) && t == Tbool)
3419 if (t && t != Tnone && t != Tbool) {
3423 type_err(c, "error: expected %1%r, found %2",
3424 e->left, type, rules, t);
3430 ###### interp binode cases
3432 while (rvtype == Tnone &&
3435 rv = interp_exec(c, b->left, &rvtype);
3436 b = cast(binode, b->right);
3440 ### The Print statement
3442 `print` is a simple statement that takes a comma-separated list of
3443 expressions and prints the values separated by spaces and terminated
3444 by a newline. No control of formatting is possible.
3446 `print` faces the same list-ordering issue as blocks, and uses the
3452 ##### expr precedence
3455 ###### SimpleStatement Grammar
3457 | print ExpressionList ${
3458 $0 = reorder_bilist($<2);
3460 | print ExpressionList , ${
3465 $0 = reorder_bilist($0);
3476 ExpressionList -> ExpressionList , Expression ${
3489 ###### print binode cases
3492 do_indent(indent, "print");
3496 print_exec(b->left, -1, bracket);
3500 b = cast(binode, b->right);
3506 ###### propagate binode cases
3509 /* don't care but all must be consistent */
3510 propagate_types(b->left, c, ok, NULL, Rnolabel);
3511 propagate_types(b->right, c, ok, NULL, Rnolabel);
3514 ###### interp binode cases
3520 for ( ; b; b = cast(binode, b->right))
3524 left = interp_exec(c, b->left, <ype);
3525 print_value(ltype, &left);
3526 free_value(ltype, &left);
3537 ###### Assignment statement
3539 An assignment will assign a value to a variable, providing it hasn't
3540 been declared as a constant. The analysis phase ensures that the type
3541 will be correct so the interpreter just needs to perform the
3542 calculation. There is a form of assignment which declares a new
3543 variable as well as assigning a value. If a name is assigned before
3544 it is declared, and error will be raised as the name is created as
3545 `Tlabel` and it is illegal to assign to such names.
3551 ###### declare terminals
3554 ###### SimpleStatement Grammar
3555 | Variable = Expression ${
3561 | VariableDecl = Expression ${
3569 if ($1->var->where_set == NULL) {
3571 "Variable declared with no type or value: %v",
3581 ###### print binode cases
3584 do_indent(indent, "");
3585 print_exec(b->left, indent, bracket);
3587 print_exec(b->right, indent, bracket);
3594 struct variable *v = cast(var, b->left)->var;
3595 do_indent(indent, "");
3596 print_exec(b->left, indent, bracket);
3597 if (cast(var, b->left)->var->constant) {
3599 if (v->where_decl == v->where_set) {
3600 type_print(v->type, stdout);
3605 if (v->where_decl == v->where_set) {
3606 type_print(v->type, stdout);
3612 print_exec(b->right, indent, bracket);
3619 ###### propagate binode cases
3623 /* Both must match and not be labels,
3624 * Type must support 'dup',
3625 * For Assign, left must not be constant.
3628 t = propagate_types(b->left, c, ok, NULL,
3629 Rnolabel | (b->op == Assign ? Rnoconstant : 0));
3634 if (propagate_types(b->right, c, ok, t, 0) != t)
3635 if (b->left->type == Xvar)
3636 type_err(c, "info: variable '%v' was set as %1 here.",
3637 cast(var, b->left)->var->where_set, t, rules, NULL);
3639 t = propagate_types(b->right, c, ok, NULL, Rnolabel);
3641 propagate_types(b->left, c, ok, t,
3642 (b->op == Assign ? Rnoconstant : 0));
3644 if (t && t->dup == NULL)
3645 type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
3650 ###### interp binode cases
3653 lleft = linterp_exec(c, b->left, <ype);
3654 right = interp_exec(c, b->right, &rtype);
3656 free_value(ltype, lleft);
3657 dup_value(ltype, &right, lleft);
3664 struct variable *v = cast(var, b->left)->var;
3667 val = var_value(c, v);
3668 free_value(v->type, val);
3669 if (v->type->prepare_type)
3670 v->type->prepare_type(c, v->type, 0);
3672 right = interp_exec(c, b->right, &rtype);
3673 memcpy(val, &right, rtype->size);
3676 val_init(v->type, val);
3681 ### The `use` statement
3683 The `use` statement is the last "simple" statement. It is needed when
3684 the condition in a conditional statement is a block. `use` works much
3685 like `return` in C, but only completes the `condition`, not the whole
3691 ###### expr precedence
3694 ###### SimpleStatement Grammar
3696 $0 = new_pos(binode, $1);
3699 if ($0->right->type == Xvar) {
3700 struct var *v = cast(var, $0->right);
3701 if (v->var->type == Tnone) {
3702 /* Convert this to a label */
3705 v->var->type = Tlabel;
3706 val = global_alloc(c, Tlabel, v->var, NULL);
3712 ###### print binode cases
3715 do_indent(indent, "use ");
3716 print_exec(b->right, -1, bracket);
3721 ###### propagate binode cases
3724 /* result matches value */
3725 return propagate_types(b->right, c, ok, type, 0);
3727 ###### interp binode cases
3730 rv = interp_exec(c, b->right, &rvtype);
3733 ### The Conditional Statement
3735 This is the biggy and currently the only complex statement. This
3736 subsumes `if`, `while`, `do/while`, `switch`, and some parts of `for`.
3737 It is comprised of a number of parts, all of which are optional though
3738 set combinations apply. Each part is (usually) a key word (`then` is
3739 sometimes optional) followed by either an expression or a code block,
3740 except the `casepart` which is a "key word and an expression" followed
3741 by a code block. The code-block option is valid for all parts and,
3742 where an expression is also allowed, the code block can use the `use`
3743 statement to report a value. If the code block does not report a value
3744 the effect is similar to reporting `True`.
3746 The `else` and `case` parts, as well as `then` when combined with
3747 `if`, can contain a `use` statement which will apply to some
3748 containing conditional statement. `for` parts, `do` parts and `then`
3749 parts used with `for` can never contain a `use`, except in some
3750 subordinate conditional statement.
3752 If there is a `forpart`, it is executed first, only once.
3753 If there is a `dopart`, then it is executed repeatedly providing
3754 always that the `condpart` or `cond`, if present, does not return a non-True
3755 value. `condpart` can fail to return any value if it simply executes
3756 to completion. This is treated the same as returning `True`.
3758 If there is a `thenpart` it will be executed whenever the `condpart`
3759 or `cond` returns True (or does not return any value), but this will happen
3760 *after* `dopart` (when present).
3762 If `elsepart` is present it will be executed at most once when the
3763 condition returns `False` or some value that isn't `True` and isn't
3764 matched by any `casepart`. If there are any `casepart`s, they will be
3765 executed when the condition returns a matching value.
3767 The particular sorts of values allowed in case parts has not yet been
3768 determined in the language design, so nothing is prohibited.
3770 The various blocks in this complex statement potentially provide scope
3771 for variables as described earlier. Each such block must include the
3772 "OpenScope" nonterminal before parsing the block, and must call
3773 `var_block_close()` when closing the block.
3775 The code following "`if`", "`switch`" and "`for`" does not get its own
3776 scope, but is in a scope covering the whole statement, so names
3777 declared there cannot be redeclared elsewhere. Similarly the
3778 condition following "`while`" is in a scope the covers the body
3779 ("`do`" part) of the loop, and which does not allow conditional scope
3780 extension. Code following "`then`" (both looping and non-looping),
3781 "`else`" and "`case`" each get their own local scope.
3783 The type requirements on the code block in a `whilepart` are quite
3784 unusal. It is allowed to return a value of some identifiable type, in
3785 which case the loop aborts and an appropriate `casepart` is run, or it
3786 can return a Boolean, in which case the loop either continues to the
3787 `dopart` (on `True`) or aborts and runs the `elsepart` (on `False`).
3788 This is different both from the `ifpart` code block which is expected to
3789 return a Boolean, or the `switchpart` code block which is expected to
3790 return the same type as the casepart values. The correct analysis of
3791 the type of the `whilepart` code block is the reason for the
3792 `Rboolok` flag which is passed to `propagate_types()`.
3794 The `cond_statement` cannot fit into a `binode` so a new `exec` is
3795 defined. As there are two scopes which cover multiple parts - one for
3796 the whole statement and one for "while" and "do" - and as we will use
3797 the 'struct exec' to track scopes, we actually need two new types of
3798 exec. One is a `binode` for the looping part, the rest is the
3799 `cond_statement`. The `cond_statement` will use an auxilliary `struct
3800 casepart` to track a list of case parts.
3811 struct exec *action;
3812 struct casepart *next;
3814 struct cond_statement {
3816 struct exec *forpart, *condpart, *thenpart, *elsepart;
3817 struct binode *looppart;
3818 struct casepart *casepart;
3821 ###### ast functions
3823 static void free_casepart(struct casepart *cp)
3827 free_exec(cp->value);
3828 free_exec(cp->action);
3835 static void free_cond_statement(struct cond_statement *s)
3839 free_exec(s->forpart);
3840 free_exec(s->condpart);
3841 free_exec(s->looppart);
3842 free_exec(s->thenpart);
3843 free_exec(s->elsepart);
3844 free_casepart(s->casepart);
3848 ###### free exec cases
3849 case Xcond_statement: free_cond_statement(cast(cond_statement, e)); break;
3851 ###### ComplexStatement Grammar
3852 | CondStatement ${ $0 = $<1; }$
3854 ###### expr precedence
3855 $TERM for then while do
3862 // A CondStatement must end with EOL, as does CondSuffix and
3864 // ForPart, ThenPart, SwitchPart, CasePart are non-empty and
3865 // may or may not end with EOL
3866 // WhilePart and IfPart include an appropriate Suffix
3868 // ForPart, SwitchPart, and IfPart open scopes, o we have to close
3869 // them. WhilePart opens and closes its own scope.
3870 CondStatement -> ForPart OptNL ThenPart OptNL WhilePart CondSuffix ${
3873 $0->thenpart = $<TP;
3874 $0->looppart = $<WP;
3875 var_block_close(c, CloseSequential);
3877 | ForPart OptNL WhilePart CondSuffix ${
3880 $0->looppart = $<WP;
3881 var_block_close(c, CloseSequential);
3883 | WhilePart CondSuffix ${
3885 $0->looppart = $<WP;
3887 | SwitchPart OptNL CasePart CondSuffix ${
3889 $0->condpart = $<SP;
3890 $CP->next = $0->casepart;
3891 $0->casepart = $<CP;
3892 var_block_close(c, CloseSequential);
3894 | SwitchPart : IN OptNL CasePart CondSuffix OUT Newlines ${
3896 $0->condpart = $<SP;
3897 $CP->next = $0->casepart;
3898 $0->casepart = $<CP;
3899 var_block_close(c, CloseSequential);
3901 | IfPart IfSuffix ${
3903 $0->condpart = $IP.condpart; $IP.condpart = NULL;
3904 $0->thenpart = $IP.thenpart; $IP.thenpart = NULL;
3905 // This is where we close an "if" statement
3906 var_block_close(c, CloseSequential);
3909 CondSuffix -> IfSuffix ${
3912 | Newlines CasePart CondSuffix ${
3914 $CP->next = $0->casepart;
3915 $0->casepart = $<CP;
3917 | CasePart CondSuffix ${
3919 $CP->next = $0->casepart;
3920 $0->casepart = $<CP;
3923 IfSuffix -> Newlines ${ $0 = new(cond_statement); }$
3924 | Newlines ElsePart ${ $0 = $<EP; }$
3925 | ElsePart ${$0 = $<EP; }$
3927 ElsePart -> else OpenBlock Newlines ${
3928 $0 = new(cond_statement);
3929 $0->elsepart = $<OB;
3930 var_block_close(c, CloseElse);
3932 | else OpenScope CondStatement ${
3933 $0 = new(cond_statement);
3934 $0->elsepart = $<CS;
3935 var_block_close(c, CloseElse);
3939 CasePart -> case Expression OpenScope ColonBlock ${
3940 $0 = calloc(1,sizeof(struct casepart));
3943 var_block_close(c, CloseParallel);
3947 // These scopes are closed in CondStatement
3948 ForPart -> for OpenBlock ${
3952 ThenPart -> then OpenBlock ${
3954 var_block_close(c, CloseSequential);
3958 // This scope is closed in CondStatement
3959 WhilePart -> while UseBlock OptNL do OpenBlock ${
3964 var_block_close(c, CloseSequential);
3965 var_block_close(c, CloseSequential);
3967 | while OpenScope Expression OpenScope ColonBlock ${
3972 var_block_close(c, CloseSequential);
3973 var_block_close(c, CloseSequential);
3977 IfPart -> if UseBlock OptNL then OpenBlock ${
3980 var_block_close(c, CloseParallel);
3982 | if OpenScope Expression OpenScope ColonBlock ${
3985 var_block_close(c, CloseParallel);
3987 | if OpenScope Expression OpenScope OptNL then Block ${
3990 var_block_close(c, CloseParallel);
3994 // This scope is closed in CondStatement
3995 SwitchPart -> switch OpenScope Expression ${
3998 | switch UseBlock ${
4002 ###### print binode cases
4004 if (b->left && b->left->type == Xbinode &&
4005 cast(binode, b->left)->op == Block) {
4007 do_indent(indent, "while {\n");
4009 do_indent(indent, "while\n");
4010 print_exec(b->left, indent+1, bracket);
4012 do_indent(indent, "} do {\n");
4014 do_indent(indent, "do\n");
4015 print_exec(b->right, indent+1, bracket);
4017 do_indent(indent, "}\n");
4019 do_indent(indent, "while ");
4020 print_exec(b->left, 0, bracket);
4025 print_exec(b->right, indent+1, bracket);
4027 do_indent(indent, "}\n");
4031 ###### print exec cases
4033 case Xcond_statement:
4035 struct cond_statement *cs = cast(cond_statement, e);
4036 struct casepart *cp;
4038 do_indent(indent, "for");
4039 if (bracket) printf(" {\n"); else printf("\n");
4040 print_exec(cs->forpart, indent+1, bracket);
4043 do_indent(indent, "} then {\n");
4045 do_indent(indent, "then\n");
4046 print_exec(cs->thenpart, indent+1, bracket);
4048 if (bracket) do_indent(indent, "}\n");
4051 print_exec(cs->looppart, indent, bracket);
4055 do_indent(indent, "switch");
4057 do_indent(indent, "if");
4058 if (cs->condpart && cs->condpart->type == Xbinode &&
4059 cast(binode, cs->condpart)->op == Block) {
4064 print_exec(cs->condpart, indent+1, bracket);
4066 do_indent(indent, "}\n");
4068 do_indent(indent, "then\n");
4069 print_exec(cs->thenpart, indent+1, bracket);
4073 print_exec(cs->condpart, 0, bracket);
4079 print_exec(cs->thenpart, indent+1, bracket);
4081 do_indent(indent, "}\n");
4086 for (cp = cs->casepart; cp; cp = cp->next) {
4087 do_indent(indent, "case ");
4088 print_exec(cp->value, -1, 0);
4093 print_exec(cp->action, indent+1, bracket);
4095 do_indent(indent, "}\n");
4098 do_indent(indent, "else");
4103 print_exec(cs->elsepart, indent+1, bracket);
4105 do_indent(indent, "}\n");
4110 ###### propagate binode cases
4112 t = propagate_types(b->right, c, ok, Tnone, 0);
4113 if (!type_compat(Tnone, t, 0))
4114 *ok = 0; // UNTESTED
4115 return propagate_types(b->left, c, ok, type, rules);
4117 ###### propagate exec cases
4118 case Xcond_statement:
4120 // forpart and looppart->right must return Tnone
4121 // thenpart must return Tnone if there is a loopart,
4122 // otherwise it is like elsepart.
4124 // be bool if there is no casepart
4125 // match casepart->values if there is a switchpart
4126 // either be bool or match casepart->value if there
4128 // elsepart and casepart->action must match the return type
4129 // expected of this statement.
4130 struct cond_statement *cs = cast(cond_statement, prog);
4131 struct casepart *cp;
4133 t = propagate_types(cs->forpart, c, ok, Tnone, 0);
4134 if (!type_compat(Tnone, t, 0))
4135 *ok = 0; // UNTESTED
4138 t = propagate_types(cs->thenpart, c, ok, Tnone, 0);
4139 if (!type_compat(Tnone, t, 0))
4140 *ok = 0; // UNTESTED
4142 if (cs->casepart == NULL) {
4143 propagate_types(cs->condpart, c, ok, Tbool, 0);
4144 propagate_types(cs->looppart, c, ok, Tbool, 0);
4146 /* Condpart must match case values, with bool permitted */
4148 for (cp = cs->casepart;
4149 cp && !t; cp = cp->next)
4150 t = propagate_types(cp->value, c, ok, NULL, 0);
4151 if (!t && cs->condpart)
4152 t = propagate_types(cs->condpart, c, ok, NULL, Rboolok); // UNTESTED
4153 if (!t && cs->looppart)
4154 t = propagate_types(cs->looppart, c, ok, NULL, Rboolok); // UNTESTED
4155 // Now we have a type (I hope) push it down
4157 for (cp = cs->casepart; cp; cp = cp->next)
4158 propagate_types(cp->value, c, ok, t, 0);
4159 propagate_types(cs->condpart, c, ok, t, Rboolok);
4160 propagate_types(cs->looppart, c, ok, t, Rboolok);
4163 // (if)then, else, and case parts must return expected type.
4164 if (!cs->looppart && !type)
4165 type = propagate_types(cs->thenpart, c, ok, NULL, rules);
4167 type = propagate_types(cs->elsepart, c, ok, NULL, rules);
4168 for (cp = cs->casepart;
4170 cp = cp->next) // UNTESTED
4171 type = propagate_types(cp->action, c, ok, NULL, rules); // UNTESTED
4174 propagate_types(cs->thenpart, c, ok, type, rules);
4175 propagate_types(cs->elsepart, c, ok, type, rules);
4176 for (cp = cs->casepart; cp ; cp = cp->next)
4177 propagate_types(cp->action, c, ok, type, rules);
4183 ###### interp binode cases
4185 // This just performs one iterration of the loop
4186 rv = interp_exec(c, b->left, &rvtype);
4187 if (rvtype == Tnone ||
4188 (rvtype == Tbool && rv.bool != 0))
4189 // cnd is Tnone or Tbool, doesn't need to be freed
4190 interp_exec(c, b->right, NULL);
4193 ###### interp exec cases
4194 case Xcond_statement:
4196 struct value v, cnd;
4197 struct type *vtype, *cndtype;
4198 struct casepart *cp;
4199 struct cond_statement *cs = cast(cond_statement, e);
4202 interp_exec(c, cs->forpart, NULL);
4204 while ((cnd = interp_exec(c, cs->looppart, &cndtype)),
4205 cndtype == Tnone || (cndtype == Tbool && cnd.bool != 0))
4206 interp_exec(c, cs->thenpart, NULL);
4208 cnd = interp_exec(c, cs->condpart, &cndtype);
4209 if ((cndtype == Tnone ||
4210 (cndtype == Tbool && cnd.bool != 0))) {
4211 // cnd is Tnone or Tbool, doesn't need to be freed
4212 rv = interp_exec(c, cs->thenpart, &rvtype);
4213 // skip else (and cases)
4217 for (cp = cs->casepart; cp; cp = cp->next) {
4218 v = interp_exec(c, cp->value, &vtype);
4219 if (value_cmp(cndtype, vtype, &v, &cnd) == 0) {
4220 free_value(vtype, &v);
4221 free_value(cndtype, &cnd);
4222 rv = interp_exec(c, cp->action, &rvtype);
4225 free_value(vtype, &v);
4227 free_value(cndtype, &cnd);
4229 rv = interp_exec(c, cs->elsepart, &rvtype);
4236 ### Top level structure
4238 All the language elements so far can be used in various places. Now
4239 it is time to clarify what those places are.
4241 At the top level of a file there will be a number of declarations.
4242 Many of the things that can be declared haven't been described yet,
4243 such as functions, procedures, imports, and probably more.
4244 For now there are two sorts of things that can appear at the top
4245 level. They are predefined constants, `struct` types, and the `main`
4246 function. While the syntax will allow the `main` function to appear
4247 multiple times, that will trigger an error if it is actually attempted.
4249 The various declarations do not return anything. They store the
4250 various declarations in the parse context.
4252 ###### Parser: grammar
4255 Ocean -> OptNL DeclarationList
4257 ## declare terminals
4264 DeclarationList -> Declaration
4265 | DeclarationList Declaration
4267 Declaration -> ERROR Newlines ${
4268 tok_err(c, // UNTESTED
4269 "error: unhandled parse error", &$1);
4275 ## top level grammar
4279 ### The `const` section
4281 As well as being defined in with the code that uses them, constants
4282 can be declared at the top level. These have full-file scope, so they
4283 are always `InScope`. The value of a top level constant can be given
4284 as an expression, and this is evaluated immediately rather than in the
4285 later interpretation stage. Once we add functions to the language, we
4286 will need rules concern which, if any, can be used to define a top
4289 Constants are defined in a section that starts with the reserved word
4290 `const` and then has a block with a list of assignment statements.
4291 For syntactic consistency, these must use the double-colon syntax to
4292 make it clear that they are constants. Type can also be given: if
4293 not, the type will be determined during analysis, as with other
4296 As the types constants are inserted at the head of a list, printing
4297 them in the same order that they were read is not straight forward.
4298 We take a quadratic approach here and count the number of constants
4299 (variables of depth 0), then count down from there, each time
4300 searching through for the Nth constant for decreasing N.
4302 ###### top level grammar
4306 DeclareConstant -> const { IN OptNL ConstList OUT OptNL } Newlines
4307 | const { SimpleConstList } Newlines
4308 | const IN OptNL ConstList OUT Newlines
4309 | const SimpleConstList Newlines
4311 ConstList -> ConstList SimpleConstLine
4313 SimpleConstList -> SimpleConstList ; Const
4316 SimpleConstLine -> SimpleConstList Newlines
4317 | ERROR Newlines ${ tok_err(c, "Syntax error in constant", &$1); }$
4320 CType -> Type ${ $0 = $<1; }$
4323 Const -> IDENTIFIER :: CType = Expression ${ {
4327 v = var_decl(c, $1.txt);
4329 struct var *var = new_pos(var, $1);
4330 v->where_decl = var;
4335 v = var_ref(c, $1.txt);
4336 tok_err(c, "error: name already declared", &$1);
4337 type_err(c, "info: this is where '%v' was first declared",
4338 v->where_decl, NULL, 0, NULL);
4342 propagate_types($5, c, &ok, $3, 0);
4347 struct value res = interp_exec(c, $5, &v->type);
4348 global_alloc(c, v->type, v, &res);
4352 ###### print const decls
4357 while (target != 0) {
4359 for (v = context.in_scope; v; v=v->in_scope)
4360 if (v->depth == 0) {
4371 struct value *val = var_value(&context, v);
4372 printf(" %.*s :: ", v->name->name.len, v->name->name.txt);
4373 type_print(v->type, stdout);
4375 if (v->type == Tstr)
4377 print_value(v->type, val);
4378 if (v->type == Tstr)
4386 ### Finally the whole `main` function.
4388 An Ocean program can currently have only one function - `main` - and
4389 that must exist. It expects an array of strings with a provided size.
4390 Following this is a `block` which is the code to execute.
4392 As this is the top level, several things are handled a bit
4394 The function is not interpreted by `interp_exec` as that isn't
4395 passed the argument list which the program requires. Similarly type
4396 analysis is a bit more interesting at this level.
4398 ###### top level grammar
4400 DeclareFunction -> MainFunction ${ {
4402 type_err(c, "\"main\" defined a second time",
4408 ###### print binode cases
4411 do_indent(indent, "func main(");
4412 for (b2 = cast(binode, b->left); b2; b2 = cast(binode, b2->right)) {
4413 struct variable *v = cast(var, b2->left)->var;
4415 print_exec(b2->left, 0, 0);
4417 type_print(v->type, stdout);
4423 print_exec(b->right, indent+1, bracket);
4425 do_indent(indent, "}\n");
4428 ###### propagate binode cases
4430 case Func: abort(); // NOTEST
4432 ###### core functions
4434 static int analyse_prog(struct exec *prog, struct parse_context *c)
4436 struct binode *bp = cast(binode, prog);
4440 struct type *argv_type;
4441 struct text argv_type_name = { " argv", 5 };
4446 argv_type = add_type(c, argv_type_name, &array_prototype);
4447 argv_type->array.member = Tstr;
4448 argv_type->array.unspec = 1;
4450 for (b = cast(binode, bp->left); b; b = cast(binode, b->right)) {
4454 propagate_types(b->left, c, &ok, argv_type, 0);
4456 default: /* invalid */ // NOTEST
4457 propagate_types(b->left, c, &ok, Tnone, 0); // NOTEST
4463 propagate_types(bp->right, c, &ok, Tnone, 0);
4468 /* Make sure everything is still consistent */
4469 propagate_types(bp->right, c, &ok, Tnone, 0);
4471 return 0; // UNTESTED
4476 static void interp_prog(struct parse_context *c, struct exec *prog,
4477 int argc, char **argv)
4479 struct binode *p = cast(binode, prog);
4487 al = cast(binode, p->left);
4489 struct var *v = cast(var, al->left);
4490 struct value *vl = var_value(c, v->var);
4500 mpq_set_ui(argcq, argc, 1);
4501 memcpy(var_value(c, t->array.vsize), &argcq, sizeof(argcq));
4502 t->prepare_type(c, t, 0);
4503 array_init(v->var->type, vl);
4504 for (i = 0; i < argc; i++) {
4505 struct value *vl2 = vl->array + i * v->var->type->array.member->size;
4508 arg.str.txt = argv[i];
4509 arg.str.len = strlen(argv[i]);
4510 free_value(Tstr, vl2);
4511 dup_value(Tstr, &arg, vl2);
4515 al = cast(binode, al->right);
4517 v = interp_exec(c, p, &vtype);
4518 free_value(vtype, &v);
4521 ###### interp binode cases
4522 case List: abort(); // NOTEST
4525 rv = interp_exec(c, b->right, &rvtype);
4528 ## And now to test it out.
4530 Having a language requires having a "hello world" program. I'll
4531 provide a little more than that: a program that prints "Hello world"
4532 finds the GCD of two numbers, prints the first few elements of
4533 Fibonacci, performs a binary search for a number, and a few other
4534 things which will likely grow as the languages grows.
4536 ###### File: oceani.mk
4539 @echo "===== DEMO ====="
4540 ./oceani --section "demo: hello" oceani.mdc 55 33
4546 four ::= 2 + 2 ; five ::= 10/2
4547 const pie ::= "I like Pie";
4548 cake ::= "The cake is"
4559 print "Hello World, what lovely oceans you have!"
4560 print "Are there", five, "?"
4561 print pi, pie, "but", cake
4563 A := $argv[1]; B := $argv[2]
4565 /* When a variable is defined in both branches of an 'if',
4566 * and used afterwards, the variables are merged.
4572 print "Is", A, "bigger than", B,"? ", bigger
4573 /* If a variable is not used after the 'if', no
4574 * merge happens, so types can be different
4577 double:string = "yes"
4578 print A, "is more than twice", B, "?", double
4581 print "double", B, "is", double
4586 if a > 0 and then b > 0:
4592 print "GCD of", A, "and", B,"is", a
4594 print a, "is not positive, cannot calculate GCD"
4596 print b, "is not positive, cannot calculate GCD"
4601 print "Fibonacci:", f1,f2,
4602 then togo = togo - 1
4610 /* Binary search... */
4615 mid := (lo + hi) / 2
4628 print "Yay, I found", target
4630 print "Closest I found was", lo
4635 // "middle square" PRNG. Not particularly good, but one my
4636 // Dad taught me - the first one I ever heard of.
4637 for i:=1; then i = i + 1; while i < size:
4638 n := list[i-1] * list[i-1]
4639 list[i] = (n / 100) % 10 000
4641 print "Before sort:",
4642 for i:=0; then i = i + 1; while i < size:
4646 for i := 1; then i=i+1; while i < size:
4647 for j:=i-1; then j=j-1; while j >= 0:
4648 if list[j] > list[j+1]:
4652 print " After sort:",
4653 for i:=0; then i = i + 1; while i < size:
4657 if 1 == 2 then print "yes"; else print "no"
4661 bob.alive = (bob.name == "Hello")
4662 print "bob", "is" if bob.alive else "isn't", "alive"