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
957 seen. This state includes a secondary nest depth which records the
958 outermost scope seen since the variable became conditionally in
959 scope. If a use of the name is found, the variable becomes "in
960 scope" and that secondary depth becomes the recorded scope depth.
961 If the name is declared as a new variable, the old variable becomes
962 "out of 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 struct variable *v, **vp, *v2;
1148 for (vp = &c->in_scope;
1149 (v = *vp) && v->min_depth > c->scope_depth;
1150 (v->scope == OutScope || v->name->var != v)
1151 ? (*vp = v->in_scope, 0)
1152 : ( vp = &v->in_scope, 0)) {
1153 if (v->name->var != v) {
1154 /* This is still in scope, but we haven't just
1161 case CloseParallel: /* handle PendingScope */
1165 if (c->scope_stack->child_count == 1)
1166 v->scope = PendingScope;
1167 else if (v->previous &&
1168 v->previous->scope == PendingScope)
1169 v->scope = PendingScope;
1170 else if (v->type == Tlabel) // UNTESTED
1171 v->scope = PendingScope; // UNTESTED
1172 else if (v->name->var == v) // UNTESTED
1173 v->scope = OutScope; // UNTESTED
1174 if (ct == CloseElse) {
1175 /* All Pending variables with this name
1176 * are now Conditional */
1178 v2 && v2->scope == PendingScope;
1180 v2->scope = CondScope;
1185 v2 && v2->scope == PendingScope;
1187 if (v2->type != Tlabel)
1188 v2->scope = OutScope;
1190 case OutScope: break; // UNTESTED
1193 case CloseSequential:
1194 if (v->type == Tlabel)
1195 v->scope = PendingScope;
1198 v->scope = OutScope;
1201 /* There was no 'else', so we can only become
1202 * conditional if we know the cases were exhaustive,
1203 * and that doesn't mean anything yet.
1204 * So only labels become conditional..
1207 v2 && v2->scope == PendingScope;
1209 if (v2->type == Tlabel) {
1210 v2->scope = CondScope;
1211 v2->min_depth = c->scope_depth;
1213 v2->scope = OutScope;
1216 case OutScope: break;
1225 The value of a variable is store separately from the variable, on an
1226 analogue of a stack frame. There are (currently) two frames that can be
1227 active. A global frame which currently only stores constants, and a
1228 stacked frame which stores local variables. Each variable knows if it
1229 is global or not, and what its index into the frame is.
1231 Values in the global frame are known immediately they are relevant, so
1232 the frame needs to be reallocated as it grows so it can store those
1233 values. The local frame doesn't get values until the interpreted phase
1234 is started, so there is no need to allocate until the size is known.
1236 ###### variable fields
1240 ###### parse context
1242 short global_size, global_alloc;
1244 void *global, *local;
1246 ###### ast functions
1248 static struct value *var_value(struct parse_context *c, struct variable *v)
1251 if (!c->local || !v->type)
1253 if (v->frame_pos + v->type->size > c->local_size) {
1254 printf("INVALID frame_pos\n"); // NOTEST
1257 return c->local + v->frame_pos;
1259 if (c->global_size > c->global_alloc) {
1260 int old = c->global_alloc;
1261 c->global_alloc = (c->global_size | 1023) + 1024;
1262 c->global = realloc(c->global, c->global_alloc);
1263 memset(c->global + old, 0, c->global_alloc - old);
1265 return c->global + v->frame_pos;
1268 static struct value *global_alloc(struct parse_context *c, struct type *t,
1269 struct variable *v, struct value *init)
1272 struct variable scratch;
1274 if (t->prepare_type)
1275 t->prepare_type(c, t, 1); // NOTEST
1277 if (c->global_size & (t->align - 1))
1278 c->global_size = (c->global_size + t->align) & ~(t->align-1); // UNTESTED
1283 v->frame_pos = c->global_size;
1285 c->global_size += v->type->size;
1286 ret = var_value(c, v);
1288 memcpy(ret, init, t->size);
1294 As global values are found -- struct field initializers, labels etc --
1295 `global_alloc()` is called to record the value in the global frame.
1297 When the program is fully parsed, we need to walk the list of variables
1298 to find any that weren't merged away and that aren't global, and to
1299 calculate the frame size and assign a frame position for each variable.
1300 For this we have `scope_finalize()`.
1302 ###### ast functions
1304 static void scope_finalize(struct parse_context *c)
1308 for (b = c->varlist; b; b = b->next) {
1310 for (v = b->var; v; v = v->previous) {
1311 struct type *t = v->type;
1316 if (c->local_size & (t->align - 1))
1317 c->local_size = (c->local_size + t->align) & ~(t->align-1);
1318 v->frame_pos = c->local_size;
1319 c->local_size += v->type->size;
1322 c->local = calloc(1, c->local_size);
1325 ###### free context storage
1326 free(context.global);
1327 free(context.local);
1331 Executables can be lots of different things. In many cases an
1332 executable is just an operation combined with one or two other
1333 executables. This allows for expressions and lists etc. Other times an
1334 executable is something quite specific like a constant or variable name.
1335 So we define a `struct exec` to be a general executable with a type, and
1336 a `struct binode` which is a subclass of `exec`, forms a node in a
1337 binary tree, and holds an operation. There will be other subclasses,
1338 and to access these we need to be able to `cast` the `exec` into the
1339 various other types. The first field in any `struct exec` is the type
1340 from the `exec_types` enum.
1343 #define cast(structname, pointer) ({ \
1344 const typeof( ((struct structname *)0)->type) *__mptr = &(pointer)->type; \
1345 if (__mptr && *__mptr != X##structname) abort(); \
1346 (struct structname *)( (char *)__mptr);})
1348 #define new(structname) ({ \
1349 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1350 __ptr->type = X##structname; \
1351 __ptr->line = -1; __ptr->column = -1; \
1354 #define new_pos(structname, token) ({ \
1355 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1356 __ptr->type = X##structname; \
1357 __ptr->line = token.line; __ptr->column = token.col; \
1366 enum exec_types type;
1374 struct exec *left, *right;
1377 ###### ast functions
1379 static int __fput_loc(struct exec *loc, FILE *f)
1383 if (loc->line >= 0) {
1384 fprintf(f, "%d:%d: ", loc->line, loc->column);
1387 if (loc->type == Xbinode)
1388 return __fput_loc(cast(binode,loc)->left, f) ||
1389 __fput_loc(cast(binode,loc)->right, f); // NOTEST
1392 static void fput_loc(struct exec *loc, FILE *f)
1394 if (!__fput_loc(loc, f))
1395 fprintf(f, "??:??: "); // NOTEST
1398 Each different type of `exec` node needs a number of functions defined,
1399 a bit like methods. We must be able to free it, print it, analyse it
1400 and execute it. Once we have specific `exec` types we will need to
1401 parse them too. Let's take this a bit more slowly.
1405 The parser generator requires a `free_foo` function for each struct
1406 that stores attributes and they will often be `exec`s and subtypes
1407 there-of. So we need `free_exec` which can handle all the subtypes,
1408 and we need `free_binode`.
1410 ###### ast functions
1412 static void free_binode(struct binode *b)
1417 free_exec(b->right);
1421 ###### core functions
1422 static void free_exec(struct exec *e)
1431 ###### forward decls
1433 static void free_exec(struct exec *e);
1435 ###### free exec cases
1436 case Xbinode: free_binode(cast(binode, e)); break;
1440 Printing an `exec` requires that we know the current indent level for
1441 printing line-oriented components. As will become clear later, we
1442 also want to know what sort of bracketing to use.
1444 ###### ast functions
1446 static void do_indent(int i, char *str)
1453 ###### core functions
1454 static void print_binode(struct binode *b, int indent, int bracket)
1458 ## print binode cases
1462 static void print_exec(struct exec *e, int indent, int bracket)
1468 print_binode(cast(binode, e), indent, bracket); break;
1473 ###### forward decls
1475 static void print_exec(struct exec *e, int indent, int bracket);
1479 As discussed, analysis involves propagating type requirements around the
1480 program and looking for errors.
1482 So `propagate_types` is passed an expected type (being a `struct type`
1483 pointer together with some `val_rules` flags) that the `exec` is
1484 expected to return, and returns the type that it does return, either
1485 of which can be `NULL` signifying "unknown". An `ok` flag is passed
1486 by reference. It is set to `0` when an error is found, and `2` when
1487 any change is made. If it remains unchanged at `1`, then no more
1488 propagation is needed.
1492 enum val_rules {Rnolabel = 1<<0, Rboolok = 1<<1, Rnoconstant = 2<<1};
1496 if (rules & Rnolabel)
1497 fputs(" (labels not permitted)", stderr);
1500 ###### core functions
1502 static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1503 struct type *type, int rules);
1504 static struct type *__propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1505 struct type *type, int rules)
1512 switch (prog->type) {
1515 struct binode *b = cast(binode, prog);
1517 ## propagate binode cases
1521 ## propagate exec cases
1526 static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1527 struct type *type, int rules)
1529 struct type *ret = __propagate_types(prog, c, ok, type, rules);
1538 Interpreting an `exec` doesn't require anything but the `exec`. State
1539 is stored in variables and each variable will be directly linked from
1540 within the `exec` tree. The exception to this is the `main` function
1541 which needs to look at command line arguments. This function will be
1542 interpreted separately.
1544 Each `exec` can return a value combined with a type in `struct lrval`.
1545 The type may be `Tnone` but must be non-NULL. Some `exec`s will return
1546 the location of a value, which can be updated, in `lval`. Others will
1547 set `lval` to NULL indicating that there is a value of appropriate type
1550 ###### core functions
1554 struct value rval, *lval;
1557 static struct lrval _interp_exec(struct parse_context *c, struct exec *e);
1559 static struct value interp_exec(struct parse_context *c, struct exec *e,
1560 struct type **typeret)
1562 struct lrval ret = _interp_exec(c, e);
1564 if (!ret.type) abort();
1566 *typeret = ret.type;
1568 dup_value(ret.type, ret.lval, &ret.rval);
1572 static struct value *linterp_exec(struct parse_context *c, struct exec *e,
1573 struct type **typeret)
1575 struct lrval ret = _interp_exec(c, e);
1578 *typeret = ret.type;
1580 free_value(ret.type, &ret.rval);
1584 static struct lrval _interp_exec(struct parse_context *c, struct exec *e)
1587 struct value rv = {}, *lrv = NULL;
1588 struct type *rvtype;
1590 rvtype = ret.type = Tnone;
1600 struct binode *b = cast(binode, e);
1601 struct value left, right, *lleft;
1602 struct type *ltype, *rtype;
1603 ltype = rtype = Tnone;
1605 ## interp binode cases
1607 free_value(ltype, &left);
1608 free_value(rtype, &right);
1611 ## interp exec cases
1621 Now that we have the shape of the interpreter in place we can add some
1622 complex types and connected them in to the data structures and the
1623 different phases of parse, analyse, print, interpret.
1625 Thus far we have arrays and structs.
1629 Arrays can be declared by giving a size and a type, as `[size]type' so
1630 `freq:[26]number` declares `freq` to be an array of 26 numbers. The
1631 size can be either a literal number, or a named constant. Some day an
1632 arbitrary expression will be supported.
1634 As a formal parameter to a function, the array can be declared with a
1635 new variable as the size: `name:[size::number]string`. The `size`
1636 variable is set to the size of the array and must be a constant. As
1637 `number` is the only supported type, it can be left out:
1638 `name:[size::]string`.
1640 Arrays cannot be assigned. When pointers are introduced we will also
1641 introduce array slices which can refer to part or all of an array -
1642 the assignment syntax will create a slice. For now, an array can only
1643 ever be referenced by the name it is declared with. It is likely that
1644 a "`copy`" primitive will eventually be define which can be used to
1645 make a copy of an array with controllable recursive depth.
1647 For now we have two sorts of array, those with fixed size either because
1648 it is given as a literal number or because it is a struct member (which
1649 cannot have a runtime-changing size), and those with a size that is
1650 determined at runtime - local variables with a const size. The former
1651 have their size calculated at parse time, the latter at run time.
1653 For the latter type, the `size` field of the type is the size of a
1654 pointer, and the array is reallocated every time it comes into scope.
1656 We differentiate struct fields with a const size from local variables
1657 with a const size by whether they are prepared at parse time or not.
1659 ###### type union fields
1662 int unspec; // size is unspecified - vsize must be set.
1665 struct variable *vsize;
1666 struct type *member;
1669 ###### value union fields
1670 void *array; // used if not static_size
1672 ###### value functions
1674 static void array_prepare_type(struct parse_context *c, struct type *type,
1677 struct value *vsize;
1679 if (!type->array.vsize || type->array.static_size)
1682 vsize = var_value(c, type->array.vsize);
1684 mpz_tdiv_q(q, mpq_numref(vsize->num), mpq_denref(vsize->num));
1685 type->array.size = mpz_get_si(q);
1689 type->array.static_size = 1;
1690 type->size = type->array.size * type->array.member->size;
1691 type->align = type->array.member->align;
1695 static void array_init(struct type *type, struct value *val)
1698 void *ptr = val->ptr;
1702 if (!type->array.static_size) {
1703 val->array = calloc(type->array.size,
1704 type->array.member->size);
1707 for (i = 0; i < type->array.size; i++) {
1709 v = (void*)ptr + i * type->array.member->size;
1710 val_init(type->array.member, v);
1714 static void array_free(struct type *type, struct value *val)
1717 void *ptr = val->ptr;
1719 if (!type->array.static_size)
1721 for (i = 0; i < type->array.size; i++) {
1723 v = (void*)ptr + i * type->array.member->size;
1724 free_value(type->array.member, v);
1726 if (!type->array.static_size)
1730 static int array_compat(struct type *require, struct type *have)
1732 if (have->compat != require->compat)
1733 return 0; // UNTESTED
1734 /* Both are arrays, so we can look at details */
1735 if (!type_compat(require->array.member, have->array.member, 0))
1737 if (have->array.unspec && require->array.unspec) {
1738 if (have->array.vsize && require->array.vsize &&
1739 have->array.vsize != require->array.vsize) // UNTESTED
1740 /* sizes might not be the same */
1741 return 0; // UNTESTED
1744 if (have->array.unspec || require->array.unspec)
1745 return 1; // UNTESTED
1746 if (require->array.vsize == NULL && have->array.vsize == NULL)
1747 return require->array.size == have->array.size;
1749 return require->array.vsize == have->array.vsize; // UNTESTED
1752 static void array_print_type(struct type *type, FILE *f)
1755 if (type->array.vsize) {
1756 struct binding *b = type->array.vsize->name;
1757 fprintf(f, "%.*s%s]", b->name.len, b->name.txt,
1758 type->array.unspec ? "::" : "");
1760 fprintf(f, "%d]", type->array.size);
1761 type_print(type->array.member, f);
1764 static struct type array_prototype = {
1766 .prepare_type = array_prepare_type,
1767 .print_type = array_print_type,
1768 .compat = array_compat,
1770 .size = sizeof(void*),
1771 .align = sizeof(void*),
1774 ###### declare terminals
1779 | [ NUMBER ] Type ${ {
1782 struct text noname = { "", 0 };
1785 $0 = t = add_type(c, noname, &array_prototype);
1786 t->array.member = $<4;
1787 t->array.vsize = NULL;
1788 if (number_parse(num, tail, $2.txt) == 0)
1789 tok_err(c, "error: unrecognised number", &$2);
1791 tok_err(c, "error: unsupported number suffix", &$2);
1793 t->array.size = mpz_get_ui(mpq_numref(num));
1794 if (mpz_cmp_ui(mpq_denref(num), 1) != 0) {
1795 tok_err(c, "error: array size must be an integer",
1797 } else if (mpz_cmp_ui(mpq_numref(num), 1UL << 30) >= 0)
1798 tok_err(c, "error: array size is too large",
1802 t->array.static_size = 1;
1803 t->size = t->array.size * t->array.member->size;
1804 t->align = t->array.member->align;
1807 | [ IDENTIFIER ] Type ${ {
1808 struct variable *v = var_ref(c, $2.txt);
1809 struct text noname = { "", 0 };
1812 tok_err(c, "error: name undeclared", &$2);
1813 else if (!v->constant)
1814 tok_err(c, "error: array size must be a constant", &$2);
1816 $0 = add_type(c, noname, &array_prototype);
1817 $0->array.member = $<4;
1819 $0->array.vsize = v;
1824 OptType -> Type ${ $0 = $<1; }$
1827 ###### formal type grammar
1829 | [ IDENTIFIER :: OptType ] Type ${ {
1830 struct variable *v = var_decl(c, $ID.txt);
1831 struct text noname = { "", 0 };
1837 $0 = add_type(c, noname, &array_prototype);
1838 $0->array.member = $<6;
1840 $0->array.unspec = 1;
1841 $0->array.vsize = v;
1847 ###### variable grammar
1849 | Variable [ Expression ] ${ {
1850 struct binode *b = new(binode);
1857 ###### print binode cases
1859 print_exec(b->left, -1, bracket);
1861 print_exec(b->right, -1, bracket);
1865 ###### propagate binode cases
1867 /* left must be an array, right must be a number,
1868 * result is the member type of the array
1870 propagate_types(b->right, c, ok, Tnum, 0);
1871 t = propagate_types(b->left, c, ok, NULL, rules & Rnoconstant);
1872 if (!t || t->compat != array_compat) {
1873 type_err(c, "error: %1 cannot be indexed", prog, t, 0, NULL);
1876 if (!type_compat(type, t->array.member, rules)) {
1877 type_err(c, "error: have %1 but need %2", prog,
1878 t->array.member, rules, type);
1880 return t->array.member;
1884 ###### interp binode cases
1890 lleft = linterp_exec(c, b->left, <ype);
1891 right = interp_exec(c, b->right, &rtype);
1893 mpz_tdiv_q(q, mpq_numref(right.num), mpq_denref(right.num));
1897 if (ltype->array.static_size)
1900 ptr = *(void**)lleft;
1901 rvtype = ltype->array.member;
1902 if (i >= 0 && i < ltype->array.size)
1903 lrv = ptr + i * rvtype->size;
1905 val_init(ltype->array.member, &rv);
1912 A `struct` is a data-type that contains one or more other data-types.
1913 It differs from an array in that each member can be of a different
1914 type, and they are accessed by name rather than by number. Thus you
1915 cannot choose an element by calculation, you need to know what you
1918 The language makes no promises about how a given structure will be
1919 stored in memory - it is free to rearrange fields to suit whatever
1920 criteria seems important.
1922 Structs are declared separately from program code - they cannot be
1923 declared in-line in a variable declaration like arrays can. A struct
1924 is given a name and this name is used to identify the type - the name
1925 is not prefixed by the word `struct` as it would be in C.
1927 Structs are only treated as the same if they have the same name.
1928 Simply having the same fields in the same order is not enough. This
1929 might change once we can create structure initializers from a list of
1932 Each component datum is identified much like a variable is declared,
1933 with a name, one or two colons, and a type. The type cannot be omitted
1934 as there is no opportunity to deduce the type from usage. An initial
1935 value can be given following an equals sign, so
1937 ##### Example: a struct type
1943 would declare a type called "complex" which has two number fields,
1944 each initialised to zero.
1946 Struct will need to be declared separately from the code that uses
1947 them, so we will need to be able to print out the declaration of a
1948 struct when reprinting the whole program. So a `print_type_decl` type
1949 function will be needed.
1951 ###### type union fields
1963 ###### type functions
1964 void (*print_type_decl)(struct type *type, FILE *f);
1966 ###### value functions
1968 static void structure_init(struct type *type, struct value *val)
1972 for (i = 0; i < type->structure.nfields; i++) {
1974 v = (void*) val->ptr + type->structure.fields[i].offset;
1975 if (type->structure.fields[i].init)
1976 dup_value(type->structure.fields[i].type,
1977 type->structure.fields[i].init,
1980 val_init(type->structure.fields[i].type, v);
1984 static void structure_free(struct type *type, struct value *val)
1988 for (i = 0; i < type->structure.nfields; i++) {
1990 v = (void*)val->ptr + type->structure.fields[i].offset;
1991 free_value(type->structure.fields[i].type, v);
1995 static void structure_free_type(struct type *t)
1998 for (i = 0; i < t->structure.nfields; i++)
1999 if (t->structure.fields[i].init) {
2000 free_value(t->structure.fields[i].type,
2001 t->structure.fields[i].init);
2003 free(t->structure.fields);
2006 static struct type structure_prototype = {
2007 .init = structure_init,
2008 .free = structure_free,
2009 .free_type = structure_free_type,
2010 .print_type_decl = structure_print_type,
2024 ###### free exec cases
2026 free_exec(cast(fieldref, e)->left);
2030 ###### declare terminals
2033 ###### variable grammar
2035 | Variable . IDENTIFIER ${ {
2036 struct fieldref *fr = new_pos(fieldref, $2);
2043 ###### print exec cases
2047 struct fieldref *f = cast(fieldref, e);
2048 print_exec(f->left, -1, bracket);
2049 printf(".%.*s", f->name.len, f->name.txt);
2053 ###### ast functions
2054 static int find_struct_index(struct type *type, struct text field)
2057 for (i = 0; i < type->structure.nfields; i++)
2058 if (text_cmp(type->structure.fields[i].name, field) == 0)
2063 ###### propagate exec cases
2067 struct fieldref *f = cast(fieldref, prog);
2068 struct type *st = propagate_types(f->left, c, ok, NULL, 0);
2071 type_err(c, "error: unknown type for field access", f->left, // UNTESTED
2073 else if (st->init != structure_init)
2074 type_err(c, "error: field reference attempted on %1, not a struct",
2075 f->left, st, 0, NULL);
2076 else if (f->index == -2) {
2077 f->index = find_struct_index(st, f->name);
2079 type_err(c, "error: cannot find requested field in %1",
2080 f->left, st, 0, NULL);
2082 if (f->index >= 0) {
2083 struct type *ft = st->structure.fields[f->index].type;
2084 if (!type_compat(type, ft, rules))
2085 type_err(c, "error: have %1 but need %2", prog,
2092 ###### interp exec cases
2095 struct fieldref *f = cast(fieldref, e);
2097 struct value *lleft = linterp_exec(c, f->left, <ype);
2098 lrv = (void*)lleft->ptr + ltype->structure.fields[f->index].offset;
2099 rvtype = ltype->structure.fields[f->index].type;
2105 struct fieldlist *prev;
2109 ###### ast functions
2110 static void free_fieldlist(struct fieldlist *f)
2114 free_fieldlist(f->prev);
2116 free_value(f->f.type, f->f.init); // UNTESTED
2117 free(f->f.init); // UNTESTED
2122 ###### top level grammar
2123 DeclareStruct -> struct IDENTIFIER FieldBlock Newlines ${ {
2125 add_type(c, $2.txt, &structure_prototype);
2127 struct fieldlist *f;
2129 for (f = $3; f; f=f->prev)
2132 t->structure.nfields = cnt;
2133 t->structure.fields = calloc(cnt, sizeof(struct field));
2136 int a = f->f.type->align;
2138 t->structure.fields[cnt] = f->f;
2139 if (t->size & (a-1))
2140 t->size = (t->size | (a-1)) + 1;
2141 t->structure.fields[cnt].offset = t->size;
2142 t->size += ((f->f.type->size - 1) | (a-1)) + 1;
2151 FieldBlock -> { IN OptNL FieldLines OUT OptNL } ${ $0 = $<FL; }$
2152 | { SimpleFieldList } ${ $0 = $<SFL; }$
2153 | IN OptNL FieldLines OUT ${ $0 = $<FL; }$
2154 | SimpleFieldList EOL ${ $0 = $<SFL; }$
2156 FieldLines -> SimpleFieldList Newlines ${ $0 = $<SFL; }$
2157 | FieldLines SimpleFieldList Newlines ${
2162 SimpleFieldList -> Field ${ $0 = $<F; }$
2163 | SimpleFieldList ; Field ${
2167 | SimpleFieldList ; ${
2170 | ERROR ${ tok_err(c, "Syntax error in struct field", &$1); }$
2172 Field -> IDENTIFIER : Type = Expression ${ {
2175 $0 = calloc(1, sizeof(struct fieldlist));
2176 $0->f.name = $1.txt;
2181 propagate_types($<5, c, &ok, $3, 0);
2184 c->parse_error = 1; // UNTESTED
2186 struct value vl = interp_exec(c, $5, NULL);
2187 $0->f.init = global_alloc(c, $0->f.type, NULL, &vl);
2190 | IDENTIFIER : Type ${
2191 $0 = calloc(1, sizeof(struct fieldlist));
2192 $0->f.name = $1.txt;
2194 if ($0->f.type->prepare_type)
2195 $0->f.type->prepare_type(c, $0->f.type, 1);
2198 ###### forward decls
2199 static void structure_print_type(struct type *t, FILE *f);
2201 ###### value functions
2202 static void structure_print_type(struct type *t, FILE *f) // UNTESTED
2206 fprintf(f, "struct %.*s\n", t->name.len, t->name.txt);
2208 for (i = 0; i < t->structure.nfields; i++) {
2209 struct field *fl = t->structure.fields + i;
2210 fprintf(f, " %.*s : ", fl->name.len, fl->name.txt);
2211 type_print(fl->type, f);
2212 if (fl->type->print && fl->init) {
2214 if (fl->type == Tstr)
2215 fprintf(f, "\""); // UNTESTED
2216 print_value(fl->type, fl->init);
2217 if (fl->type == Tstr)
2218 fprintf(f, "\""); // UNTESTED
2224 ###### print type decls
2226 struct type *t; // UNTESTED
2229 while (target != 0) {
2231 for (t = context.typelist; t ; t=t->next)
2232 if (t->print_type_decl) {
2241 t->print_type_decl(t, stdout);
2249 A function is a named chunk of code which can be passed parameters and
2250 can return results. Each function has an implicit type which includes
2251 the set of parameters and the return value. As yet these types cannot
2252 be declared separate from the function itself.
2254 In fact, only one function is currently possible - `main`. `main` is
2255 passed an array of strings together with the size of the array, and
2256 doesn't return anything. The strings are command line arguments.
2258 The parameters can be specified either in parentheses as a list, such as
2260 ##### Example: function 1
2262 func main(av:[ac::number]string)
2265 or as an indented list of one parameter per line
2267 ##### Example: function 2
2270 argv:[argc::number]string
2282 MainFunction -> func main ( OpenScope Args ) Block Newlines ${
2285 $0->left = reorder_bilist($<Ar);
2287 var_block_close(c, CloseSequential);
2288 if (c->scope_stack && !c->parse_error) abort();
2290 | func main IN OpenScope OptNL Args OUT OptNL do Block Newlines ${
2293 $0->left = reorder_bilist($<Ar);
2295 var_block_close(c, CloseSequential);
2296 if (c->scope_stack && !c->parse_error) abort();
2298 | func main NEWLINE OpenScope OptNL do Block Newlines ${
2303 var_block_close(c, CloseSequential);
2304 if (c->scope_stack && !c->parse_error) abort();
2307 Args -> ${ $0 = NULL; }$
2308 | Varlist ${ $0 = $<1; }$
2309 | Varlist ; ${ $0 = $<1; }$
2310 | Varlist NEWLINE ${ $0 = $<1; }$
2312 Varlist -> Varlist ; ArgDecl ${ // UNTESTED
2326 ArgDecl -> IDENTIFIER : FormalType ${ {
2327 struct variable *v = var_decl(c, $1.txt);
2333 ## Executables: the elements of code
2335 Each code element needs to be parsed, printed, analysed,
2336 interpreted, and freed. There are several, so let's just start with
2337 the easy ones and work our way up.
2341 We have already met values as separate objects. When manifest
2342 constants appear in the program text, that must result in an executable
2343 which has a constant value. So the `val` structure embeds a value in
2356 ###### ast functions
2357 struct val *new_val(struct type *T, struct token tk)
2359 struct val *v = new_pos(val, tk);
2370 $0 = new_val(Tbool, $1);
2374 $0 = new_val(Tbool, $1);
2378 $0 = new_val(Tnum, $1);
2381 if (number_parse($0->val.num, tail, $1.txt) == 0)
2382 mpq_init($0->val.num); // UNTESTED
2384 tok_err(c, "error: unsupported number suffix",
2389 $0 = new_val(Tstr, $1);
2392 string_parse(&$1, '\\', &$0->val.str, tail);
2394 tok_err(c, "error: unsupported string suffix",
2399 $0 = new_val(Tstr, $1);
2402 string_parse(&$1, '\\', &$0->val.str, tail);
2404 tok_err(c, "error: unsupported string suffix",
2409 ###### print exec cases
2412 struct val *v = cast(val, e);
2413 if (v->vtype == Tstr)
2415 print_value(v->vtype, &v->val);
2416 if (v->vtype == Tstr)
2421 ###### propagate exec cases
2424 struct val *val = cast(val, prog);
2425 if (!type_compat(type, val->vtype, rules))
2426 type_err(c, "error: expected %1%r found %2",
2427 prog, type, rules, val->vtype);
2431 ###### interp exec cases
2433 rvtype = cast(val, e)->vtype;
2434 dup_value(rvtype, &cast(val, e)->val, &rv);
2437 ###### ast functions
2438 static void free_val(struct val *v)
2441 free_value(v->vtype, &v->val);
2445 ###### free exec cases
2446 case Xval: free_val(cast(val, e)); break;
2448 ###### ast functions
2449 // Move all nodes from 'b' to 'rv', reversing their order.
2450 // In 'b' 'left' is a list, and 'right' is the last node.
2451 // In 'rv', left' is the first node and 'right' is a list.
2452 static struct binode *reorder_bilist(struct binode *b)
2454 struct binode *rv = NULL;
2457 struct exec *t = b->right;
2461 b = cast(binode, b->left);
2471 Just as we used a `val` to wrap a value into an `exec`, we similarly
2472 need a `var` to wrap a `variable` into an exec. While each `val`
2473 contained a copy of the value, each `var` holds a link to the variable
2474 because it really is the same variable no matter where it appears.
2475 When a variable is used, we need to remember to follow the `->merged`
2476 link to find the primary instance.
2484 struct variable *var;
2492 VariableDecl -> IDENTIFIER : ${ {
2493 struct variable *v = var_decl(c, $1.txt);
2494 $0 = new_pos(var, $1);
2499 v = var_ref(c, $1.txt);
2501 type_err(c, "error: variable '%v' redeclared",
2503 type_err(c, "info: this is where '%v' was first declared",
2504 v->where_decl, NULL, 0, NULL);
2507 | IDENTIFIER :: ${ {
2508 struct variable *v = var_decl(c, $1.txt);
2509 $0 = new_pos(var, $1);
2515 v = var_ref(c, $1.txt);
2517 type_err(c, "error: variable '%v' redeclared",
2519 type_err(c, "info: this is where '%v' was first declared",
2520 v->where_decl, NULL, 0, NULL);
2523 | IDENTIFIER : Type ${ {
2524 struct variable *v = var_decl(c, $1.txt);
2525 $0 = new_pos(var, $1);
2532 v = var_ref(c, $1.txt);
2534 type_err(c, "error: variable '%v' redeclared",
2536 type_err(c, "info: this is where '%v' was first declared",
2537 v->where_decl, NULL, 0, NULL);
2540 | IDENTIFIER :: Type ${ {
2541 struct variable *v = var_decl(c, $1.txt);
2542 $0 = new_pos(var, $1);
2550 v = var_ref(c, $1.txt);
2552 type_err(c, "error: variable '%v' redeclared",
2554 type_err(c, "info: this is where '%v' was first declared",
2555 v->where_decl, NULL, 0, NULL);
2560 Variable -> IDENTIFIER ${ {
2561 struct variable *v = var_ref(c, $1.txt);
2562 $0 = new_pos(var, $1);
2564 /* This might be a label - allocate a var just in case */
2565 v = var_decl(c, $1.txt);
2572 cast(var, $0)->var = v;
2576 ###### print exec cases
2579 struct var *v = cast(var, e);
2581 struct binding *b = v->var->name;
2582 printf("%.*s", b->name.len, b->name.txt);
2589 if (loc && loc->type == Xvar) {
2590 struct var *v = cast(var, loc);
2592 struct binding *b = v->var->name;
2593 fprintf(stderr, "%.*s", b->name.len, b->name.txt);
2595 fputs("???", stderr); // NOTEST
2597 fputs("NOTVAR", stderr); // NOTEST
2600 ###### propagate exec cases
2604 struct var *var = cast(var, prog);
2605 struct variable *v = var->var;
2607 type_err(c, "%d:BUG: no variable!!", prog, NULL, 0, NULL); // NOTEST
2608 return Tnone; // NOTEST
2611 if (v->constant && (rules & Rnoconstant)) {
2612 type_err(c, "error: Cannot assign to a constant: %v",
2613 prog, NULL, 0, NULL);
2614 type_err(c, "info: name was defined as a constant here",
2615 v->where_decl, NULL, 0, NULL);
2618 if (v->type == Tnone && v->where_decl == prog)
2619 type_err(c, "error: variable used but not declared: %v",
2620 prog, NULL, 0, NULL);
2621 if (v->type == NULL) {
2622 if (type && *ok != 0) {
2624 v->where_set = prog;
2629 if (!type_compat(type, v->type, rules)) {
2630 type_err(c, "error: expected %1%r but variable '%v' is %2", prog,
2631 type, rules, v->type);
2632 type_err(c, "info: this is where '%v' was set to %1", v->where_set,
2633 v->type, rules, NULL);
2640 ###### interp exec cases
2643 struct var *var = cast(var, e);
2644 struct variable *v = var->var;
2647 lrv = var_value(c, v);
2652 ###### ast functions
2654 static void free_var(struct var *v)
2659 ###### free exec cases
2660 case Xvar: free_var(cast(var, e)); break;
2662 ### Expressions: Conditional
2664 Our first user of the `binode` will be conditional expressions, which
2665 is a bit odd as they actually have three components. That will be
2666 handled by having 2 binodes for each expression. The conditional
2667 expression is the lowest precedence operator which is why we define it
2668 first - to start the precedence list.
2670 Conditional expressions are of the form "value `if` condition `else`
2671 other_value". They associate to the right, so everything to the right
2672 of `else` is part of an else value, while only a higher-precedence to
2673 the left of `if` is the if values. Between `if` and `else` there is no
2674 room for ambiguity, so a full conditional expression is allowed in
2686 Expression -> Expression if Expression else Expression $$ifelse ${ {
2687 struct binode *b1 = new(binode);
2688 struct binode *b2 = new(binode);
2697 ## expression grammar
2699 ###### print binode cases
2702 b2 = cast(binode, b->right);
2703 if (bracket) printf("(");
2704 print_exec(b2->left, -1, bracket);
2706 print_exec(b->left, -1, bracket);
2708 print_exec(b2->right, -1, bracket);
2709 if (bracket) printf(")");
2712 ###### propagate binode cases
2715 /* cond must be Tbool, others must match */
2716 struct binode *b2 = cast(binode, b->right);
2719 propagate_types(b->left, c, ok, Tbool, 0);
2720 t = propagate_types(b2->left, c, ok, type, Rnolabel);
2721 t2 = propagate_types(b2->right, c, ok, type ?: t, Rnolabel);
2725 ###### interp binode cases
2728 struct binode *b2 = cast(binode, b->right);
2729 left = interp_exec(c, b->left, <ype);
2731 rv = interp_exec(c, b2->left, &rvtype); // UNTESTED
2733 rv = interp_exec(c, b2->right, &rvtype);
2737 ### Expressions: Boolean
2739 The next class of expressions to use the `binode` will be Boolean
2740 expressions. "`and then`" and "`or else`" are similar to `and` and `or`
2741 have same corresponding precendence. The difference is that they don't
2742 evaluate the second expression if not necessary.
2751 ###### expr precedence
2756 ###### expression grammar
2757 | Expression or Expression ${ {
2758 struct binode *b = new(binode);
2764 | Expression or else Expression ${ {
2765 struct binode *b = new(binode);
2772 | Expression and Expression ${ {
2773 struct binode *b = new(binode);
2779 | Expression and then Expression ${ {
2780 struct binode *b = new(binode);
2787 | not Expression ${ {
2788 struct binode *b = new(binode);
2794 ###### print binode cases
2796 if (bracket) printf("(");
2797 print_exec(b->left, -1, bracket);
2799 print_exec(b->right, -1, bracket);
2800 if (bracket) printf(")");
2803 if (bracket) printf("(");
2804 print_exec(b->left, -1, bracket);
2805 printf(" and then ");
2806 print_exec(b->right, -1, bracket);
2807 if (bracket) printf(")");
2810 if (bracket) printf("(");
2811 print_exec(b->left, -1, bracket);
2813 print_exec(b->right, -1, bracket);
2814 if (bracket) printf(")");
2817 if (bracket) printf("(");
2818 print_exec(b->left, -1, bracket);
2819 printf(" or else ");
2820 print_exec(b->right, -1, bracket);
2821 if (bracket) printf(")");
2824 if (bracket) printf("(");
2826 print_exec(b->right, -1, bracket);
2827 if (bracket) printf(")");
2830 ###### propagate binode cases
2836 /* both must be Tbool, result is Tbool */
2837 propagate_types(b->left, c, ok, Tbool, 0);
2838 propagate_types(b->right, c, ok, Tbool, 0);
2839 if (type && type != Tbool)
2840 type_err(c, "error: %1 operation found where %2 expected", prog,
2844 ###### interp binode cases
2846 rv = interp_exec(c, b->left, &rvtype);
2847 right = interp_exec(c, b->right, &rtype);
2848 rv.bool = rv.bool && right.bool;
2851 rv = interp_exec(c, b->left, &rvtype);
2853 rv = interp_exec(c, b->right, NULL);
2856 rv = interp_exec(c, b->left, &rvtype);
2857 right = interp_exec(c, b->right, &rtype);
2858 rv.bool = rv.bool || right.bool;
2861 rv = interp_exec(c, b->left, &rvtype);
2863 rv = interp_exec(c, b->right, NULL);
2866 rv = interp_exec(c, b->right, &rvtype);
2870 ### Expressions: Comparison
2872 Of slightly higher precedence that Boolean expressions are Comparisons.
2873 A comparison takes arguments of any comparable type, but the two types
2876 To simplify the parsing we introduce an `eop` which can record an
2877 expression operator, and the `CMPop` non-terminal will match one of them.
2884 ###### ast functions
2885 static void free_eop(struct eop *e)
2899 ###### expr precedence
2900 $LEFT < > <= >= == != CMPop
2902 ###### expression grammar
2903 | Expression CMPop Expression ${ {
2904 struct binode *b = new(binode);
2914 CMPop -> < ${ $0.op = Less; }$
2915 | > ${ $0.op = Gtr; }$
2916 | <= ${ $0.op = LessEq; }$
2917 | >= ${ $0.op = GtrEq; }$
2918 | == ${ $0.op = Eql; }$
2919 | != ${ $0.op = NEql; }$
2921 ###### print binode cases
2929 if (bracket) printf("(");
2930 print_exec(b->left, -1, bracket);
2932 case Less: printf(" < "); break;
2933 case LessEq: printf(" <= "); break;
2934 case Gtr: printf(" > "); break;
2935 case GtrEq: printf(" >= "); break;
2936 case Eql: printf(" == "); break;
2937 case NEql: printf(" != "); break;
2938 default: abort(); // NOTEST
2940 print_exec(b->right, -1, bracket);
2941 if (bracket) printf(")");
2944 ###### propagate binode cases
2951 /* Both must match but not be labels, result is Tbool */
2952 t = propagate_types(b->left, c, ok, NULL, Rnolabel);
2954 propagate_types(b->right, c, ok, t, 0);
2956 t = propagate_types(b->right, c, ok, NULL, Rnolabel); // UNTESTED
2958 t = propagate_types(b->left, c, ok, t, 0); // UNTESTED
2960 if (!type_compat(type, Tbool, 0))
2961 type_err(c, "error: Comparison returns %1 but %2 expected", prog,
2962 Tbool, rules, type);
2965 ###### interp binode cases
2974 left = interp_exec(c, b->left, <ype);
2975 right = interp_exec(c, b->right, &rtype);
2976 cmp = value_cmp(ltype, rtype, &left, &right);
2979 case Less: rv.bool = cmp < 0; break;
2980 case LessEq: rv.bool = cmp <= 0; break;
2981 case Gtr: rv.bool = cmp > 0; break;
2982 case GtrEq: rv.bool = cmp >= 0; break;
2983 case Eql: rv.bool = cmp == 0; break;
2984 case NEql: rv.bool = cmp != 0; break;
2985 default: rv.bool = 0; break; // NOTEST
2990 ### Expressions: The rest
2992 The remaining expressions with the highest precedence are arithmetic,
2993 string concatenation, and string conversion. String concatenation
2994 (`++`) has the same precedence as multiplication and division, but lower
2997 String conversion is a temporary feature until I get a better type
2998 system. `$` is a prefix operator which expects a string and returns
3001 `+` and `-` are both infix and prefix operations (where they are
3002 absolute value and negation). These have different operator names.
3004 We also have a 'Bracket' operator which records where parentheses were
3005 found. This makes it easy to reproduce these when printing. Possibly I
3006 should only insert brackets were needed for precedence.
3016 ###### expr precedence
3022 ###### expression grammar
3023 | Expression Eop Expression ${ {
3024 struct binode *b = new(binode);
3031 | Expression Top Expression ${ {
3032 struct binode *b = new(binode);
3039 | ( Expression ) ${ {
3040 struct binode *b = new_pos(binode, $1);
3045 | Uop Expression ${ {
3046 struct binode *b = new(binode);
3051 | Value ${ $0 = $<1; }$
3052 | Variable ${ $0 = $<1; }$
3055 Eop -> + ${ $0.op = Plus; }$
3056 | - ${ $0.op = Minus; }$
3058 Uop -> + ${ $0.op = Absolute; }$
3059 | - ${ $0.op = Negate; }$
3060 | $ ${ $0.op = StringConv; }$
3062 Top -> * ${ $0.op = Times; }$
3063 | / ${ $0.op = Divide; }$
3064 | % ${ $0.op = Rem; }$
3065 | ++ ${ $0.op = Concat; }$
3067 ###### print binode cases
3074 if (bracket) printf("(");
3075 print_exec(b->left, indent, bracket);
3077 case Plus: fputs(" + ", stdout); break;
3078 case Minus: fputs(" - ", stdout); break;
3079 case Times: fputs(" * ", stdout); break;
3080 case Divide: fputs(" / ", stdout); break;
3081 case Rem: fputs(" % ", stdout); break;
3082 case Concat: fputs(" ++ ", stdout); break;
3083 default: abort(); // NOTEST
3085 print_exec(b->right, indent, bracket);
3086 if (bracket) printf(")");
3091 if (bracket) printf("(");
3093 case Absolute: fputs("+", stdout); break;
3094 case Negate: fputs("-", stdout); break;
3095 case StringConv: fputs("$", stdout); break;
3096 default: abort(); // NOTEST
3098 print_exec(b->right, indent, bracket);
3099 if (bracket) printf(")");
3103 print_exec(b->right, indent, bracket);
3107 ###### propagate binode cases
3113 /* both must be numbers, result is Tnum */
3116 /* as propagate_types ignores a NULL,
3117 * unary ops fit here too */
3118 propagate_types(b->left, c, ok, Tnum, 0);
3119 propagate_types(b->right, c, ok, Tnum, 0);
3120 if (!type_compat(type, Tnum, 0))
3121 type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
3126 /* both must be Tstr, result is Tstr */
3127 propagate_types(b->left, c, ok, Tstr, 0);
3128 propagate_types(b->right, c, ok, Tstr, 0);
3129 if (!type_compat(type, Tstr, 0))
3130 type_err(c, "error: Concat returns %1 but %2 expected", prog,
3135 /* op must be string, result is number */
3136 propagate_types(b->left, c, ok, Tstr, 0);
3137 if (!type_compat(type, Tnum, 0))
3138 type_err(c, // UNTESTED
3139 "error: Can only convert string to number, not %1",
3140 prog, type, 0, NULL);
3144 return propagate_types(b->right, c, ok, type, 0);
3146 ###### interp binode cases
3149 rv = interp_exec(c, b->left, &rvtype);
3150 right = interp_exec(c, b->right, &rtype);
3151 mpq_add(rv.num, rv.num, right.num);
3154 rv = interp_exec(c, b->left, &rvtype);
3155 right = interp_exec(c, b->right, &rtype);
3156 mpq_sub(rv.num, rv.num, right.num);
3159 rv = interp_exec(c, b->left, &rvtype);
3160 right = interp_exec(c, b->right, &rtype);
3161 mpq_mul(rv.num, rv.num, right.num);
3164 rv = interp_exec(c, b->left, &rvtype);
3165 right = interp_exec(c, b->right, &rtype);
3166 mpq_div(rv.num, rv.num, right.num);
3171 left = interp_exec(c, b->left, <ype);
3172 right = interp_exec(c, b->right, &rtype);
3173 mpz_init(l); mpz_init(r); mpz_init(rem);
3174 mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
3175 mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
3176 mpz_tdiv_r(rem, l, r);
3177 val_init(Tnum, &rv);
3178 mpq_set_z(rv.num, rem);
3179 mpz_clear(r); mpz_clear(l); mpz_clear(rem);
3184 rv = interp_exec(c, b->right, &rvtype);
3185 mpq_neg(rv.num, rv.num);
3188 rv = interp_exec(c, b->right, &rvtype);
3189 mpq_abs(rv.num, rv.num);
3192 rv = interp_exec(c, b->right, &rvtype);
3195 left = interp_exec(c, b->left, <ype);
3196 right = interp_exec(c, b->right, &rtype);
3198 rv.str = text_join(left.str, right.str);
3201 right = interp_exec(c, b->right, &rvtype);
3205 struct text tx = right.str;
3208 if (tx.txt[0] == '-') {
3209 neg = 1; // UNTESTED
3210 tx.txt++; // UNTESTED
3211 tx.len--; // UNTESTED
3213 if (number_parse(rv.num, tail, tx) == 0)
3214 mpq_init(rv.num); // UNTESTED
3216 mpq_neg(rv.num, rv.num); // UNTESTED
3218 printf("Unsupported suffix: %.*s\n", tx.len, tx.txt); // UNTESTED
3222 ###### value functions
3224 static struct text text_join(struct text a, struct text b)
3227 rv.len = a.len + b.len;
3228 rv.txt = malloc(rv.len);
3229 memcpy(rv.txt, a.txt, a.len);
3230 memcpy(rv.txt+a.len, b.txt, b.len);
3234 ### Blocks, Statements, and Statement lists.
3236 Now that we have expressions out of the way we need to turn to
3237 statements. There are simple statements and more complex statements.
3238 Simple statements do not contain (syntactic) newlines, complex statements do.
3240 Statements often come in sequences and we have corresponding simple
3241 statement lists and complex statement lists.
3242 The former comprise only simple statements separated by semicolons.
3243 The later comprise complex statements and simple statement lists. They are
3244 separated by newlines. Thus the semicolon is only used to separate
3245 simple statements on the one line. This may be overly restrictive,
3246 but I'm not sure I ever want a complex statement to share a line with
3249 Note that a simple statement list can still use multiple lines if
3250 subsequent lines are indented, so
3252 ###### Example: wrapped simple statement list
3257 is a single simple statement list. This might allow room for
3258 confusion, so I'm not set on it yet.
3260 A simple statement list needs no extra syntax. A complex statement
3261 list has two syntactic forms. It can be enclosed in braces (much like
3262 C blocks), or it can be introduced by an indent and continue until an
3263 unindented newline (much like Python blocks). With this extra syntax
3264 it is referred to as a block.
3266 Note that a block does not have to include any newlines if it only
3267 contains simple statements. So both of:
3269 if condition: a=b; d=f
3271 if condition { a=b; print f }
3275 In either case the list is constructed from a `binode` list with
3276 `Block` as the operator. When parsing the list it is most convenient
3277 to append to the end, so a list is a list and a statement. When using
3278 the list it is more convenient to consider a list to be a statement
3279 and a list. So we need a function to re-order a list.
3280 `reorder_bilist` serves this purpose.
3282 The only stand-alone statement we introduce at this stage is `pass`
3283 which does nothing and is represented as a `NULL` pointer in a `Block`
3284 list. Other stand-alone statements will follow once the infrastructure
3295 Block -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3296 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3297 | SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3298 | SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3299 | IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3301 OpenBlock -> OpenScope { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3302 | OpenScope { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3303 | OpenScope SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3304 | OpenScope SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3305 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3307 UseBlock -> { OpenScope IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3308 | { OpenScope SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3309 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3311 ColonBlock -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3312 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3313 | : SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3314 | : SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3315 | : IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3317 Statementlist -> ComplexStatements ${ $0 = reorder_bilist($<CS); }$
3319 ComplexStatements -> ComplexStatements ComplexStatement ${
3329 | ComplexStatement ${
3341 ComplexStatement -> SimpleStatements Newlines ${
3342 $0 = reorder_bilist($<SS);
3344 | SimpleStatements ; Newlines ${
3345 $0 = reorder_bilist($<SS);
3347 ## ComplexStatement Grammar
3350 SimpleStatements -> SimpleStatements ; SimpleStatement ${
3356 | SimpleStatement ${
3364 SimpleStatement -> pass ${ $0 = NULL; }$
3365 | ERROR ${ tok_err(c, "Syntax error in statement", &$1); }$
3366 ## SimpleStatement Grammar
3368 ###### print binode cases
3372 if (b->left == NULL) // UNTESTED
3373 printf("pass"); // UNTESTED
3375 print_exec(b->left, indent, bracket); // UNTESTED
3376 if (b->right) { // UNTESTED
3377 printf("; "); // UNTESTED
3378 print_exec(b->right, indent, bracket); // UNTESTED
3381 // block, one per line
3382 if (b->left == NULL)
3383 do_indent(indent, "pass\n");
3385 print_exec(b->left, indent, bracket);
3387 print_exec(b->right, indent, bracket);
3391 ###### propagate binode cases
3394 /* If any statement returns something other than Tnone
3395 * or Tbool then all such must return same type.
3396 * As each statement may be Tnone or something else,
3397 * we must always pass NULL (unknown) down, otherwise an incorrect
3398 * error might occur. We never return Tnone unless it is
3403 for (e = b; e; e = cast(binode, e->right)) {
3404 t = propagate_types(e->left, c, ok, NULL, rules);
3405 if ((rules & Rboolok) && t == Tbool)
3407 if (t && t != Tnone && t != Tbool) {
3411 type_err(c, "error: expected %1%r, found %2",
3412 e->left, type, rules, t);
3418 ###### interp binode cases
3420 while (rvtype == Tnone &&
3423 rv = interp_exec(c, b->left, &rvtype);
3424 b = cast(binode, b->right);
3428 ### The Print statement
3430 `print` is a simple statement that takes a comma-separated list of
3431 expressions and prints the values separated by spaces and terminated
3432 by a newline. No control of formatting is possible.
3434 `print` faces the same list-ordering issue as blocks, and uses the
3440 ##### expr precedence
3443 ###### SimpleStatement Grammar
3445 | print ExpressionList ${
3446 $0 = reorder_bilist($<2);
3448 | print ExpressionList , ${
3453 $0 = reorder_bilist($0);
3464 ExpressionList -> ExpressionList , Expression ${
3477 ###### print binode cases
3480 do_indent(indent, "print");
3484 print_exec(b->left, -1, bracket);
3488 b = cast(binode, b->right);
3494 ###### propagate binode cases
3497 /* don't care but all must be consistent */
3498 propagate_types(b->left, c, ok, NULL, Rnolabel);
3499 propagate_types(b->right, c, ok, NULL, Rnolabel);
3502 ###### interp binode cases
3508 for ( ; b; b = cast(binode, b->right))
3512 left = interp_exec(c, b->left, <ype);
3513 print_value(ltype, &left);
3514 free_value(ltype, &left);
3525 ###### Assignment statement
3527 An assignment will assign a value to a variable, providing it hasn't
3528 been declared as a constant. The analysis phase ensures that the type
3529 will be correct so the interpreter just needs to perform the
3530 calculation. There is a form of assignment which declares a new
3531 variable as well as assigning a value. If a name is assigned before
3532 it is declared, and error will be raised as the name is created as
3533 `Tlabel` and it is illegal to assign to such names.
3539 ###### declare terminals
3542 ###### SimpleStatement Grammar
3543 | Variable = Expression ${
3549 | VariableDecl = Expression ${
3557 if ($1->var->where_set == NULL) {
3559 "Variable declared with no type or value: %v",
3569 ###### print binode cases
3572 do_indent(indent, "");
3573 print_exec(b->left, indent, bracket);
3575 print_exec(b->right, indent, bracket);
3582 struct variable *v = cast(var, b->left)->var;
3583 do_indent(indent, "");
3584 print_exec(b->left, indent, bracket);
3585 if (cast(var, b->left)->var->constant) {
3587 if (v->where_decl == v->where_set) {
3588 type_print(v->type, stdout);
3593 if (v->where_decl == v->where_set) {
3594 type_print(v->type, stdout);
3600 print_exec(b->right, indent, bracket);
3607 ###### propagate binode cases
3611 /* Both must match and not be labels,
3612 * Type must support 'dup',
3613 * For Assign, left must not be constant.
3616 t = propagate_types(b->left, c, ok, NULL,
3617 Rnolabel | (b->op == Assign ? Rnoconstant : 0));
3622 if (propagate_types(b->right, c, ok, t, 0) != t)
3623 if (b->left->type == Xvar)
3624 type_err(c, "info: variable '%v' was set as %1 here.",
3625 cast(var, b->left)->var->where_set, t, rules, NULL);
3627 t = propagate_types(b->right, c, ok, NULL, Rnolabel);
3629 propagate_types(b->left, c, ok, t,
3630 (b->op == Assign ? Rnoconstant : 0));
3632 if (t && t->dup == NULL)
3633 type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
3638 ###### interp binode cases
3641 lleft = linterp_exec(c, b->left, <ype);
3642 right = interp_exec(c, b->right, &rtype);
3644 free_value(ltype, lleft);
3645 dup_value(ltype, &right, lleft);
3652 struct variable *v = cast(var, b->left)->var;
3655 val = var_value(c, v);
3656 free_value(v->type, val);
3657 if (v->type->prepare_type)
3658 v->type->prepare_type(c, v->type, 0);
3660 right = interp_exec(c, b->right, &rtype);
3661 memcpy(val, &right, rtype->size);
3664 val_init(v->type, val);
3669 ### The `use` statement
3671 The `use` statement is the last "simple" statement. It is needed when
3672 the condition in a conditional statement is a block. `use` works much
3673 like `return` in C, but only completes the `condition`, not the whole
3679 ###### expr precedence
3682 ###### SimpleStatement Grammar
3684 $0 = new_pos(binode, $1);
3687 if ($0->right->type == Xvar) {
3688 struct var *v = cast(var, $0->right);
3689 if (v->var->type == Tnone) {
3690 /* Convert this to a label */
3693 v->var->type = Tlabel;
3694 val = global_alloc(c, Tlabel, v->var, NULL);
3700 ###### print binode cases
3703 do_indent(indent, "use ");
3704 print_exec(b->right, -1, bracket);
3709 ###### propagate binode cases
3712 /* result matches value */
3713 return propagate_types(b->right, c, ok, type, 0);
3715 ###### interp binode cases
3718 rv = interp_exec(c, b->right, &rvtype);
3721 ### The Conditional Statement
3723 This is the biggy and currently the only complex statement. This
3724 subsumes `if`, `while`, `do/while`, `switch`, and some parts of `for`.
3725 It is comprised of a number of parts, all of which are optional though
3726 set combinations apply. Each part is (usually) a key word (`then` is
3727 sometimes optional) followed by either an expression or a code block,
3728 except the `casepart` which is a "key word and an expression" followed
3729 by a code block. The code-block option is valid for all parts and,
3730 where an expression is also allowed, the code block can use the `use`
3731 statement to report a value. If the code block does not report a value
3732 the effect is similar to reporting `True`.
3734 The `else` and `case` parts, as well as `then` when combined with
3735 `if`, can contain a `use` statement which will apply to some
3736 containing conditional statement. `for` parts, `do` parts and `then`
3737 parts used with `for` can never contain a `use`, except in some
3738 subordinate conditional statement.
3740 If there is a `forpart`, it is executed first, only once.
3741 If there is a `dopart`, then it is executed repeatedly providing
3742 always that the `condpart` or `cond`, if present, does not return a non-True
3743 value. `condpart` can fail to return any value if it simply executes
3744 to completion. This is treated the same as returning `True`.
3746 If there is a `thenpart` it will be executed whenever the `condpart`
3747 or `cond` returns True (or does not return any value), but this will happen
3748 *after* `dopart` (when present).
3750 If `elsepart` is present it will be executed at most once when the
3751 condition returns `False` or some value that isn't `True` and isn't
3752 matched by any `casepart`. If there are any `casepart`s, they will be
3753 executed when the condition returns a matching value.
3755 The particular sorts of values allowed in case parts has not yet been
3756 determined in the language design, so nothing is prohibited.
3758 The various blocks in this complex statement potentially provide scope
3759 for variables as described earlier. Each such block must include the
3760 "OpenScope" nonterminal before parsing the block, and must call
3761 `var_block_close()` when closing the block.
3763 The code following "`if`", "`switch`" and "`for`" does not get its own
3764 scope, but is in a scope covering the whole statement, so names
3765 declared there cannot be redeclared elsewhere. Similarly the
3766 condition following "`while`" is in a scope the covers the body
3767 ("`do`" part) of the loop, and which does not allow conditional scope
3768 extension. Code following "`then`" (both looping and non-looping),
3769 "`else`" and "`case`" each get their own local scope.
3771 The type requirements on the code block in a `whilepart` are quite
3772 unusal. It is allowed to return a value of some identifiable type, in
3773 which case the loop aborts and an appropriate `casepart` is run, or it
3774 can return a Boolean, in which case the loop either continues to the
3775 `dopart` (on `True`) or aborts and runs the `elsepart` (on `False`).
3776 This is different both from the `ifpart` code block which is expected to
3777 return a Boolean, or the `switchpart` code block which is expected to
3778 return the same type as the casepart values. The correct analysis of
3779 the type of the `whilepart` code block is the reason for the
3780 `Rboolok` flag which is passed to `propagate_types()`.
3782 The `cond_statement` cannot fit into a `binode` so a new `exec` is
3783 defined. As there are two scopes which cover multiple parts - one for
3784 the whole statement and one for "while" and "do" - and as we will use
3785 the 'struct exec' to track scopes, we actually need two new types of
3786 exec. One is a `binode` for the looping part, the rest is the
3787 `cond_statement`. The `cond_statement` will use an auxilliary `struct
3788 casepart` to track a list of case parts.
3799 struct exec *action;
3800 struct casepart *next;
3802 struct cond_statement {
3804 struct exec *forpart, *condpart, *thenpart, *elsepart;
3805 struct binode *looppart;
3806 struct casepart *casepart;
3809 ###### ast functions
3811 static void free_casepart(struct casepart *cp)
3815 free_exec(cp->value);
3816 free_exec(cp->action);
3823 static void free_cond_statement(struct cond_statement *s)
3827 free_exec(s->forpart);
3828 free_exec(s->condpart);
3829 free_exec(s->looppart);
3830 free_exec(s->thenpart);
3831 free_exec(s->elsepart);
3832 free_casepart(s->casepart);
3836 ###### free exec cases
3837 case Xcond_statement: free_cond_statement(cast(cond_statement, e)); break;
3839 ###### ComplexStatement Grammar
3840 | CondStatement ${ $0 = $<1; }$
3842 ###### expr precedence
3843 $TERM for then while do
3850 // A CondStatement must end with EOL, as does CondSuffix and
3852 // ForPart, ThenPart, SwitchPart, CasePart are non-empty and
3853 // may or may not end with EOL
3854 // WhilePart and IfPart include an appropriate Suffix
3856 // ForPart, SwitchPart, and IfPart open scopes, o we have to close
3857 // them. WhilePart opens and closes its own scope.
3858 CondStatement -> ForPart OptNL ThenPart OptNL WhilePart CondSuffix ${
3861 $0->thenpart = $<TP;
3862 $0->looppart = $<WP;
3863 var_block_close(c, CloseSequential);
3865 | ForPart OptNL WhilePart CondSuffix ${
3868 $0->looppart = $<WP;
3869 var_block_close(c, CloseSequential);
3871 | WhilePart CondSuffix ${
3873 $0->looppart = $<WP;
3875 | SwitchPart OptNL CasePart CondSuffix ${
3877 $0->condpart = $<SP;
3878 $CP->next = $0->casepart;
3879 $0->casepart = $<CP;
3880 var_block_close(c, CloseSequential);
3882 | SwitchPart : IN OptNL CasePart CondSuffix OUT Newlines ${
3884 $0->condpart = $<SP;
3885 $CP->next = $0->casepart;
3886 $0->casepart = $<CP;
3887 var_block_close(c, CloseSequential);
3889 | IfPart IfSuffix ${
3891 $0->condpart = $IP.condpart; $IP.condpart = NULL;
3892 $0->thenpart = $IP.thenpart; $IP.thenpart = NULL;
3893 // This is where we close an "if" statement
3894 var_block_close(c, CloseSequential);
3897 CondSuffix -> IfSuffix ${
3900 | Newlines CasePart CondSuffix ${
3902 $CP->next = $0->casepart;
3903 $0->casepart = $<CP;
3905 | CasePart CondSuffix ${
3907 $CP->next = $0->casepart;
3908 $0->casepart = $<CP;
3911 IfSuffix -> Newlines ${ $0 = new(cond_statement); }$
3912 | Newlines ElsePart ${ $0 = $<EP; }$
3913 | ElsePart ${$0 = $<EP; }$
3915 ElsePart -> else OpenBlock Newlines ${
3916 $0 = new(cond_statement);
3917 $0->elsepart = $<OB;
3918 var_block_close(c, CloseElse);
3920 | else OpenScope CondStatement ${
3921 $0 = new(cond_statement);
3922 $0->elsepart = $<CS;
3923 var_block_close(c, CloseElse);
3927 CasePart -> case Expression OpenScope ColonBlock ${
3928 $0 = calloc(1,sizeof(struct casepart));
3931 var_block_close(c, CloseParallel);
3935 // These scopes are closed in CondStatement
3936 ForPart -> for OpenBlock ${
3940 ThenPart -> then OpenBlock ${
3942 var_block_close(c, CloseSequential);
3946 // This scope is closed in CondStatement
3947 WhilePart -> while UseBlock OptNL do OpenBlock ${
3952 var_block_close(c, CloseSequential);
3953 var_block_close(c, CloseSequential);
3955 | while OpenScope Expression OpenScope ColonBlock ${
3960 var_block_close(c, CloseSequential);
3961 var_block_close(c, CloseSequential);
3965 IfPart -> if UseBlock OptNL then OpenBlock ${
3968 var_block_close(c, CloseParallel);
3970 | if OpenScope Expression OpenScope ColonBlock ${
3973 var_block_close(c, CloseParallel);
3975 | if OpenScope Expression OpenScope OptNL then Block ${
3978 var_block_close(c, CloseParallel);
3982 // This scope is closed in CondStatement
3983 SwitchPart -> switch OpenScope Expression ${
3986 | switch UseBlock ${
3990 ###### print binode cases
3992 if (b->left && b->left->type == Xbinode &&
3993 cast(binode, b->left)->op == Block) {
3995 do_indent(indent, "while {\n");
3997 do_indent(indent, "while\n");
3998 print_exec(b->left, indent+1, bracket);
4000 do_indent(indent, "} do {\n");
4002 do_indent(indent, "do\n");
4003 print_exec(b->right, indent+1, bracket);
4005 do_indent(indent, "}\n");
4007 do_indent(indent, "while ");
4008 print_exec(b->left, 0, bracket);
4013 print_exec(b->right, indent+1, bracket);
4015 do_indent(indent, "}\n");
4019 ###### print exec cases
4021 case Xcond_statement:
4023 struct cond_statement *cs = cast(cond_statement, e);
4024 struct casepart *cp;
4026 do_indent(indent, "for");
4027 if (bracket) printf(" {\n"); else printf("\n");
4028 print_exec(cs->forpart, indent+1, bracket);
4031 do_indent(indent, "} then {\n");
4033 do_indent(indent, "then\n");
4034 print_exec(cs->thenpart, indent+1, bracket);
4036 if (bracket) do_indent(indent, "}\n");
4039 print_exec(cs->looppart, indent, bracket);
4043 do_indent(indent, "switch");
4045 do_indent(indent, "if");
4046 if (cs->condpart && cs->condpart->type == Xbinode &&
4047 cast(binode, cs->condpart)->op == Block) {
4052 print_exec(cs->condpart, indent+1, bracket);
4054 do_indent(indent, "}\n");
4056 do_indent(indent, "then\n");
4057 print_exec(cs->thenpart, indent+1, bracket);
4061 print_exec(cs->condpart, 0, bracket);
4067 print_exec(cs->thenpart, indent+1, bracket);
4069 do_indent(indent, "}\n");
4074 for (cp = cs->casepart; cp; cp = cp->next) {
4075 do_indent(indent, "case ");
4076 print_exec(cp->value, -1, 0);
4081 print_exec(cp->action, indent+1, bracket);
4083 do_indent(indent, "}\n");
4086 do_indent(indent, "else");
4091 print_exec(cs->elsepart, indent+1, bracket);
4093 do_indent(indent, "}\n");
4098 ###### propagate binode cases
4100 t = propagate_types(b->right, c, ok, Tnone, 0);
4101 if (!type_compat(Tnone, t, 0))
4102 *ok = 0; // UNTESTED
4103 return propagate_types(b->left, c, ok, type, rules);
4105 ###### propagate exec cases
4106 case Xcond_statement:
4108 // forpart and looppart->right must return Tnone
4109 // thenpart must return Tnone if there is a loopart,
4110 // otherwise it is like elsepart.
4112 // be bool if there is no casepart
4113 // match casepart->values if there is a switchpart
4114 // either be bool or match casepart->value if there
4116 // elsepart and casepart->action must match the return type
4117 // expected of this statement.
4118 struct cond_statement *cs = cast(cond_statement, prog);
4119 struct casepart *cp;
4121 t = propagate_types(cs->forpart, c, ok, Tnone, 0);
4122 if (!type_compat(Tnone, t, 0))
4123 *ok = 0; // UNTESTED
4126 t = propagate_types(cs->thenpart, c, ok, Tnone, 0);
4127 if (!type_compat(Tnone, t, 0))
4128 *ok = 0; // UNTESTED
4130 if (cs->casepart == NULL) {
4131 propagate_types(cs->condpart, c, ok, Tbool, 0);
4132 propagate_types(cs->looppart, c, ok, Tbool, 0);
4134 /* Condpart must match case values, with bool permitted */
4136 for (cp = cs->casepart;
4137 cp && !t; cp = cp->next)
4138 t = propagate_types(cp->value, c, ok, NULL, 0);
4139 if (!t && cs->condpart)
4140 t = propagate_types(cs->condpart, c, ok, NULL, Rboolok); // UNTESTED
4141 if (!t && cs->looppart)
4142 t = propagate_types(cs->looppart, c, ok, NULL, Rboolok); // UNTESTED
4143 // Now we have a type (I hope) push it down
4145 for (cp = cs->casepart; cp; cp = cp->next)
4146 propagate_types(cp->value, c, ok, t, 0);
4147 propagate_types(cs->condpart, c, ok, t, Rboolok);
4148 propagate_types(cs->looppart, c, ok, t, Rboolok);
4151 // (if)then, else, and case parts must return expected type.
4152 if (!cs->looppart && !type)
4153 type = propagate_types(cs->thenpart, c, ok, NULL, rules);
4155 type = propagate_types(cs->elsepart, c, ok, NULL, rules);
4156 for (cp = cs->casepart;
4158 cp = cp->next) // UNTESTED
4159 type = propagate_types(cp->action, c, ok, NULL, rules); // UNTESTED
4162 propagate_types(cs->thenpart, c, ok, type, rules);
4163 propagate_types(cs->elsepart, c, ok, type, rules);
4164 for (cp = cs->casepart; cp ; cp = cp->next)
4165 propagate_types(cp->action, c, ok, type, rules);
4171 ###### interp binode cases
4173 // This just performs one iterration of the loop
4174 rv = interp_exec(c, b->left, &rvtype);
4175 if (rvtype == Tnone ||
4176 (rvtype == Tbool && rv.bool != 0))
4177 // cnd is Tnone or Tbool, doesn't need to be freed
4178 interp_exec(c, b->right, NULL);
4181 ###### interp exec cases
4182 case Xcond_statement:
4184 struct value v, cnd;
4185 struct type *vtype, *cndtype;
4186 struct casepart *cp;
4187 struct cond_statement *cs = cast(cond_statement, e);
4190 interp_exec(c, cs->forpart, NULL);
4192 while ((cnd = interp_exec(c, cs->looppart, &cndtype)),
4193 cndtype == Tnone || (cndtype == Tbool && cnd.bool != 0))
4194 interp_exec(c, cs->thenpart, NULL);
4196 cnd = interp_exec(c, cs->condpart, &cndtype);
4197 if ((cndtype == Tnone ||
4198 (cndtype == Tbool && cnd.bool != 0))) {
4199 // cnd is Tnone or Tbool, doesn't need to be freed
4200 rv = interp_exec(c, cs->thenpart, &rvtype);
4201 // skip else (and cases)
4205 for (cp = cs->casepart; cp; cp = cp->next) {
4206 v = interp_exec(c, cp->value, &vtype);
4207 if (value_cmp(cndtype, vtype, &v, &cnd) == 0) {
4208 free_value(vtype, &v);
4209 free_value(cndtype, &cnd);
4210 rv = interp_exec(c, cp->action, &rvtype);
4213 free_value(vtype, &v);
4215 free_value(cndtype, &cnd);
4217 rv = interp_exec(c, cs->elsepart, &rvtype);
4224 ### Top level structure
4226 All the language elements so far can be used in various places. Now
4227 it is time to clarify what those places are.
4229 At the top level of a file there will be a number of declarations.
4230 Many of the things that can be declared haven't been described yet,
4231 such as functions, procedures, imports, and probably more.
4232 For now there are two sorts of things that can appear at the top
4233 level. They are predefined constants, `struct` types, and the `main`
4234 function. While the syntax will allow the `main` function to appear
4235 multiple times, that will trigger an error if it is actually attempted.
4237 The various declarations do not return anything. They store the
4238 various declarations in the parse context.
4240 ###### Parser: grammar
4243 Ocean -> OptNL DeclarationList
4245 ## declare terminals
4252 DeclarationList -> Declaration
4253 | DeclarationList Declaration
4255 Declaration -> ERROR Newlines ${
4256 tok_err(c, // UNTESTED
4257 "error: unhandled parse error", &$1);
4263 ## top level grammar
4267 ### The `const` section
4269 As well as being defined in with the code that uses them, constants
4270 can be declared at the top level. These have full-file scope, so they
4271 are always `InScope`. The value of a top level constant can be given
4272 as an expression, and this is evaluated immediately rather than in the
4273 later interpretation stage. Once we add functions to the language, we
4274 will need rules concern which, if any, can be used to define a top
4277 Constants are defined in a section that starts with the reserved word
4278 `const` and then has a block with a list of assignment statements.
4279 For syntactic consistency, these must use the double-colon syntax to
4280 make it clear that they are constants. Type can also be given: if
4281 not, the type will be determined during analysis, as with other
4284 As the types constants are inserted at the head of a list, printing
4285 them in the same order that they were read is not straight forward.
4286 We take a quadratic approach here and count the number of constants
4287 (variables of depth 0), then count down from there, each time
4288 searching through for the Nth constant for decreasing N.
4290 ###### top level grammar
4294 DeclareConstant -> const { IN OptNL ConstList OUT OptNL } Newlines
4295 | const { SimpleConstList } Newlines
4296 | const IN OptNL ConstList OUT Newlines
4297 | const SimpleConstList Newlines
4299 ConstList -> ConstList SimpleConstLine
4301 SimpleConstList -> SimpleConstList ; Const
4304 SimpleConstLine -> SimpleConstList Newlines
4305 | ERROR Newlines ${ tok_err(c, "Syntax error in constant", &$1); }$
4308 CType -> Type ${ $0 = $<1; }$
4311 Const -> IDENTIFIER :: CType = Expression ${ {
4315 v = var_decl(c, $1.txt);
4317 struct var *var = new_pos(var, $1);
4318 v->where_decl = var;
4323 v = var_ref(c, $1.txt);
4324 tok_err(c, "error: name already declared", &$1);
4325 type_err(c, "info: this is where '%v' was first declared",
4326 v->where_decl, NULL, 0, NULL);
4330 propagate_types($5, c, &ok, $3, 0);
4335 struct value res = interp_exec(c, $5, &v->type);
4336 global_alloc(c, v->type, v, &res);
4340 ###### print const decls
4345 while (target != 0) {
4347 for (v = context.in_scope; v; v=v->in_scope)
4348 if (v->depth == 0) {
4359 struct value *val = var_value(&context, v);
4360 printf(" %.*s :: ", v->name->name.len, v->name->name.txt);
4361 type_print(v->type, stdout);
4363 if (v->type == Tstr)
4365 print_value(v->type, val);
4366 if (v->type == Tstr)
4374 ### Finally the whole `main` function.
4376 An Ocean program can currently have only one function - `main` - and
4377 that must exist. It expects an array of strings with a provided size.
4378 Following this is a `block` which is the code to execute.
4380 As this is the top level, several things are handled a bit
4382 The function is not interpreted by `interp_exec` as that isn't
4383 passed the argument list which the program requires. Similarly type
4384 analysis is a bit more interesting at this level.
4386 ###### top level grammar
4388 DeclareFunction -> MainFunction ${ {
4390 type_err(c, "\"main\" defined a second time",
4396 ###### print binode cases
4399 do_indent(indent, "func main(");
4400 for (b2 = cast(binode, b->left); b2; b2 = cast(binode, b2->right)) {
4401 struct variable *v = cast(var, b2->left)->var;
4403 print_exec(b2->left, 0, 0);
4405 type_print(v->type, stdout);
4411 print_exec(b->right, indent+1, bracket);
4413 do_indent(indent, "}\n");
4416 ###### propagate binode cases
4418 case Func: abort(); // NOTEST
4420 ###### core functions
4422 static int analyse_prog(struct exec *prog, struct parse_context *c)
4424 struct binode *bp = cast(binode, prog);
4428 struct type *argv_type;
4429 struct text argv_type_name = { " argv", 5 };
4434 argv_type = add_type(c, argv_type_name, &array_prototype);
4435 argv_type->array.member = Tstr;
4436 argv_type->array.unspec = 1;
4438 for (b = cast(binode, bp->left); b; b = cast(binode, b->right)) {
4442 propagate_types(b->left, c, &ok, argv_type, 0);
4444 default: /* invalid */ // NOTEST
4445 propagate_types(b->left, c, &ok, Tnone, 0); // NOTEST
4451 propagate_types(bp->right, c, &ok, Tnone, 0);
4456 /* Make sure everything is still consistent */
4457 propagate_types(bp->right, c, &ok, Tnone, 0);
4459 return 0; // UNTESTED
4464 static void interp_prog(struct parse_context *c, struct exec *prog,
4465 int argc, char **argv)
4467 struct binode *p = cast(binode, prog);
4475 al = cast(binode, p->left);
4477 struct var *v = cast(var, al->left);
4478 struct value *vl = var_value(c, v->var);
4488 mpq_set_ui(argcq, argc, 1);
4489 memcpy(var_value(c, t->array.vsize), &argcq, sizeof(argcq));
4490 t->prepare_type(c, t, 0);
4491 array_init(v->var->type, vl);
4492 for (i = 0; i < argc; i++) {
4493 struct value *vl2 = vl->array + i * v->var->type->array.member->size;
4496 arg.str.txt = argv[i];
4497 arg.str.len = strlen(argv[i]);
4498 free_value(Tstr, vl2);
4499 dup_value(Tstr, &arg, vl2);
4503 al = cast(binode, al->right);
4505 v = interp_exec(c, p, &vtype);
4506 free_value(vtype, &v);
4509 ###### interp binode cases
4510 case List: abort(); // NOTEST
4513 rv = interp_exec(c, b->right, &rvtype);
4516 ## And now to test it out.
4518 Having a language requires having a "hello world" program. I'll
4519 provide a little more than that: a program that prints "Hello world"
4520 finds the GCD of two numbers, prints the first few elements of
4521 Fibonacci, performs a binary search for a number, and a few other
4522 things which will likely grow as the languages grows.
4524 ###### File: oceani.mk
4527 @echo "===== DEMO ====="
4528 ./oceani --section "demo: hello" oceani.mdc 55 33
4534 four ::= 2 + 2 ; five ::= 10/2
4535 const pie ::= "I like Pie";
4536 cake ::= "The cake is"
4547 print "Hello World, what lovely oceans you have!"
4548 print "Are there", five, "?"
4549 print pi, pie, "but", cake
4551 A := $argv[1]; B := $argv[2]
4553 /* When a variable is defined in both branches of an 'if',
4554 * and used afterwards, the variables are merged.
4560 print "Is", A, "bigger than", B,"? ", bigger
4561 /* If a variable is not used after the 'if', no
4562 * merge happens, so types can be different
4565 double:string = "yes"
4566 print A, "is more than twice", B, "?", double
4569 print "double", B, "is", double
4574 if a > 0 and then b > 0:
4580 print "GCD of", A, "and", B,"is", a
4582 print a, "is not positive, cannot calculate GCD"
4584 print b, "is not positive, cannot calculate GCD"
4589 print "Fibonacci:", f1,f2,
4590 then togo = togo - 1
4598 /* Binary search... */
4603 mid := (lo + hi) / 2
4616 print "Yay, I found", target
4618 print "Closest I found was", lo
4623 // "middle square" PRNG. Not particularly good, but one my
4624 // Dad taught me - the first one I ever heard of.
4625 for i:=1; then i = i + 1; while i < size:
4626 n := list[i-1] * list[i-1]
4627 list[i] = (n / 100) % 10 000
4629 print "Before sort:",
4630 for i:=0; then i = i + 1; while i < size:
4634 for i := 1; then i=i+1; while i < size:
4635 for j:=i-1; then j=j-1; while j >= 0:
4636 if list[j] > list[j+1]:
4640 print " After sort:",
4641 for i:=0; then i = i + 1; while i < size:
4645 if 1 == 2 then print "yes"; else print "no"
4649 bob.alive = (bob.name == "Hello")
4650 print "bob", "is" if bob.alive else "isn't", "alive"