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 Elements that are present purely to make a usable language, and
45 without any expectation that they will remain, are the "program'
46 clause, which provides a list of variables to received command-line
47 arguments, and the "print" statement which performs simple output.
49 The current scalar types are "number", "Boolean", and "string".
50 Boolean will likely stay in its current form, the other two might, but
51 could just as easily be changed.
55 Versions of the interpreter which obviously do not support a complete
56 language will be named after creeks and streams. This one is Jamison
59 Once we have something reasonably resembling a complete language, the
60 names of rivers will be used.
61 Early versions of the compiler will be named after seas. Major
62 releases of the compiler will be named after oceans. Hopefully I will
63 be finished once I get to the Pacific Ocean release.
67 As well as parsing and executing a program, the interpreter can print
68 out the program from the parsed internal structure. This is useful
69 for validating the parsing.
70 So the main requirements of the interpreter are:
72 - Parse the program, possibly with tracing,
73 - Analyse the parsed program to ensure consistency,
75 - Execute the program, if no parsing or consistency errors were found.
77 This is all performed by a single C program extracted with
80 There will be two formats for printing the program: a default and one
81 that uses bracketing. So a `--bracket` command line option is needed
82 for that. Normally the first code section found is used, however an
83 alternate section can be requested so that a file (such as this one)
84 can contain multiple programs This is effected with the `--section`
87 This code must be compiled with `-fplan9-extensions` so that anonymous
88 structures can be used.
90 ###### File: oceani.mk
92 myCFLAGS := -Wall -g -fplan9-extensions
93 CFLAGS := $(filter-out $(myCFLAGS),$(CFLAGS)) $(myCFLAGS)
94 myLDLIBS:= libparser.o libscanner.o libmdcode.o -licuuc
95 LDLIBS := $(filter-out $(myLDLIBS),$(LDLIBS)) $(myLDLIBS)
97 all :: $(LDLIBS) oceani
98 oceani.c oceani.h : oceani.mdc parsergen
99 ./parsergen -o oceani --LALR --tag Parser oceani.mdc
100 oceani.mk: oceani.mdc md2c
103 oceani: oceani.o $(LDLIBS)
104 $(CC) $(CFLAGS) -o oceani oceani.o $(LDLIBS)
106 ###### Parser: header
109 struct parse_context {
110 struct token_config config;
119 #define container_of(ptr, type, member) ({ \
120 const typeof( ((type *)0)->member ) *__mptr = (ptr); \
121 (type *)( (char *)__mptr - offsetof(type,member) );})
123 #define config2context(_conf) container_of(_conf, struct parse_context, \
132 #include <sys/mman.h>
151 static char Usage[] = "Usage: oceani --trace --print --noexec --brackets"
152 "--section=SectionName prog.ocn\n";
153 static const struct option long_options[] = {
154 {"trace", 0, NULL, 't'},
155 {"print", 0, NULL, 'p'},
156 {"noexec", 0, NULL, 'n'},
157 {"brackets", 0, NULL, 'b'},
158 {"section", 1, NULL, 's'},
161 const char *options = "tpnbs";
162 int main(int argc, char *argv[])
167 struct section *s, *ss;
168 char *section = NULL;
169 struct parse_context context = {
171 .ignored = (1 << TK_line_comment)
172 | (1 << TK_block_comment),
173 .number_chars = ".,_+-",
178 int doprint=0, dotrace=0, doexec=1, brackets=0;
180 while ((opt = getopt_long(argc, argv, options, long_options, NULL))
183 case 't': dotrace=1; break;
184 case 'p': doprint=1; break;
185 case 'n': doexec=0; break;
186 case 'b': brackets=1; break;
187 case 's': section = optarg; break;
188 default: fprintf(stderr, Usage);
192 if (optind >= argc) {
193 fprintf(stderr, "oceani: no input file given\n");
196 fd = open(argv[optind], O_RDONLY);
198 fprintf(stderr, "oceani: cannot open %s\n", argv[optind]);
201 context.file_name = argv[optind];
202 len = lseek(fd, 0, 2);
203 file = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
204 s = code_extract(file, file+len, NULL);
206 fprintf(stderr, "oceani: could not find any code in %s\n",
211 ## context initialization
214 for (ss = s; ss; ss = ss->next) {
215 struct text sec = ss->section;
216 if (sec.len == strlen(section) &&
217 strncmp(sec.txt, section, sec.len) == 0)
221 fprintf(stderr, "oceani: cannot find section %s\n",
227 parse_oceani(ss->code, &context.config, dotrace ? stderr : NULL);
230 fprintf(stderr, "oceani: no program found.\n");
231 context.parse_error = 1;
233 if (context.prog && doprint) {
236 print_exec(context.prog, 0, brackets);
238 if (context.prog && doexec && !context.parse_error) {
239 if (!analyse_prog(context.prog, &context)) {
240 fprintf(stderr, "oceani: type error in program - not running.\n");
243 interp_prog(context.prog, argv+optind+1);
245 free_exec(context.prog);
248 struct section *t = s->next;
254 ## free context types
255 exit(context.parse_error ? 1 : 0);
260 The four requirements of parse, analyse, print, interpret apply to
261 each language element individually so that is how most of the code
264 Three of the four are fairly self explanatory. The one that requires
265 a little explanation is the analysis step.
267 The current language design does not require the types of variables to
268 be declared, but they must still have a single type. Different
269 operations impose different requirements on the variables, for example
270 addition requires both arguments to be numeric, and assignment
271 requires the variable on the left to have the same type as the
272 expression on the right.
274 Analysis involves propagating these type requirements around and
275 consequently setting the type of each variable. If any requirements
276 are violated (e.g. a string is compared with a number) or if a
277 variable needs to have two different types, then an error is raised
278 and the program will not run.
280 If the same variable is declared in both branchs of an 'if/else', or
281 in all cases of a 'switch' then the multiple instances may be merged
282 into just one variable if the variable is references after the
283 conditional statement. When this happens, the types must naturally be
284 consistent across all the branches. When the variable is not used
285 outside the if, the variables in the different branches are distinct
286 and can be of different types.
288 Determining the types of all variables early is important for
289 processing command line arguments. These can be assigned to any of
290 several types of variable, but we must first know the correct type so
291 any required conversion can happen. If a variable is associated with
292 a command line argument but no type can be interpreted (e.g. the
293 variable is only ever used in a `print` statement), then the type is
296 Undeclared names may only appear in "use" statements and "case" expressions.
297 These names are given a type of "label" and a unique value.
298 This allows them to fill the role of a name in an enumerated type, which
299 is useful for testing the `switch` statement.
301 As we will see, the condition part of a `while` statement can return
302 either a Boolean or some other type. This requires that the expected
303 type that gets passed around comprises a type and a flag to indicate
304 that `Tbool` is also permitted.
306 As there are, as yet, no distinct types that are compatible, there
307 isn't much subtlety in the analysis. When we have distinct number
308 types, this will become more interesting.
312 When analysis discovers an inconsistency it needs to report an error;
313 just refusing to run the code ensures that the error doesn't cascade,
314 but by itself it isn't very useful. A clear understanding of the sort
315 of error message that are useful will help guide the process of
318 At a simplistic level, the only sort of error that type analysis can
319 report is that the type of some construct doesn't match a contextual
320 requirement. For example, in `4 + "hello"` the addition provides a
321 contextual requirement for numbers, but `"hello"` is not a number. In
322 this particular example no further information is needed as the types
323 are obvious from local information. When a variable is involved that
324 isn't the case. It may be helpful to explain why the variable has a
325 particular type, by indicating the location where the type was set,
326 whether by declaration or usage.
328 Using a recursive-descent analysis we can easily detect a problem at
329 multiple locations. In "`hello:= "there"; 4 + hello`" the addition
330 will detect that one argument is not a number and the usage of `hello`
331 will detect that a number was wanted, but not provided. In this
332 (early) version of the language, we will generate error reports at
333 multiple locations, so the use of `hello` will report an error and
334 explain were the value was set, and the addition will report an error
335 and say why numbers are needed. To be able to report locations for
336 errors, each language element will need to record a file location
337 (line and column) and each variable will need to record the language
338 element where its type was set. For now we will assume that each line
339 of an error message indicates one location in the file, and up to 2
340 types. So we provide a `printf`-like function which takes a format, a
341 language (a `struct exec` which has not yet been introduced), and 2
342 types. "`%1`" reports the first type, "`%2`" reports the second. We
343 will need a function to print the location, once we know how that is
344 stored. As will be explained later, there are sometimes extra rules for
345 type matching and they might affect error messages, we need to pass those
348 As well as type errors, we sometimes need to report problems with
349 tokens, which might be unexpected or might name a type that has not
350 been defined. For these we have `tok_err()` which reports an error
351 with a given token. Each of the error functions sets the flag in the
352 context so indicate that parsing failed.
356 static void fput_loc(struct exec *loc, FILE *f);
358 ###### core functions
360 static void type_err(struct parse_context *c,
361 char *fmt, struct exec *loc,
362 struct type *t1, int rules, struct type *t2)
364 fprintf(stderr, "%s:", c->file_name);
365 fput_loc(loc, stderr);
366 for (; *fmt ; fmt++) {
373 case '%': fputc(*fmt, stderr); break; // NOTEST
374 default: fputc('?', stderr); break; // NOTEST
376 type_print(t1, stderr);
379 type_print(t2, stderr);
388 static void tok_err(struct parse_context *c, char *fmt, struct token *t)
390 fprintf(stderr, "%s:%d:%d: %s: %.*s\n", c->file_name, t->line, t->col, fmt,
391 t->txt.len, t->txt.txt);
395 ## Entities: declared and predeclared.
397 There are various "things" that the language and/or the interpreter
398 needs to know about to parse and execute a program. These include
399 types, variables, values, and executable code. These are all lumped
400 together under the term "entities" (calling them "objects" would be
401 confusing) and introduced here. These will introduced and described
402 here. The following section will present the different specific code
403 elements which comprise or manipulate these various entities.
407 Values come in a wide range of types, with more likely to be added.
408 Each type needs to be able to parse and print its own values (for
409 convenience at least) as well as to compare two values, at least for
410 equality and possibly for order. For now, values might need to be
411 duplicated and freed, though eventually such manipulations will be
412 better integrated into the language.
414 Rather than requiring every numeric type to support all numeric
415 operations (add, multiple, etc), we allow types to be able to present
416 as one of a few standard types: integer, float, and fraction. The
417 existence of these conversion functions eventaully enable types to
418 determine if they are compatible with other types, though such types
419 have not yet been implemented.
421 Named type are stored in a simple linked list. Objects of each type are "values"
422 which are often passed around by value.
429 ## value union fields
436 struct value (*init)(struct type *type);
437 struct value (*prepare)(struct type *type);
438 struct value (*parse)(struct type *type, char *str);
439 void (*print)(struct value val);
440 void (*print_type)(struct type *type, FILE *f);
441 int (*cmp_order)(struct value v1, struct value v2);
442 int (*cmp_eq)(struct value v1, struct value v2);
443 struct value (*dup)(struct value val);
444 void (*free)(struct value val);
445 void (*free_type)(struct type *t);
446 int (*compat)(struct type *this, struct type *other);
447 long long (*to_int)(struct value *v);
448 double (*to_float)(struct value *v);
449 int (*to_mpq)(mpq_t *q, struct value *v);
458 struct type *typelist;
462 static struct type *find_type(struct parse_context *c, struct text s)
464 struct type *l = c->typelist;
467 text_cmp(l->name, s) != 0)
472 static struct type *add_type(struct parse_context *c, struct text s,
477 n = calloc(1, sizeof(*n));
480 n->next = c->typelist;
485 static void free_type(struct type *t)
487 /* The type is always a reference to something in the
488 * context, so we don't need to free anything.
492 static void free_value(struct value v)
498 static int type_compat(struct type *require, struct type *have, int rules)
500 if ((rules & Rboolok) && have == Tbool)
502 if ((rules & Rnolabel) && have == Tlabel)
504 if (!require || !have)
508 return require->compat(require, have);
510 return require == have;
513 static void type_print(struct type *type, FILE *f)
516 fputs("*unknown*type*", f);
517 else if (type->name.len)
518 fprintf(f, "%.*s", type->name.len, type->name.txt);
519 else if (type->print_type)
520 type->print_type(type, f);
522 fputs("*invalid*type*", f); // NOTEST
525 static struct value val_prepare(struct type *type)
530 return type->prepare(type);
535 static struct value val_init(struct type *type)
540 return type->init(type);
545 static struct value dup_value(struct value v)
548 return v.type->dup(v);
552 static int value_cmp(struct value left, struct value right)
554 if (left.type && left.type->cmp_order)
555 return left.type->cmp_order(left, right);
556 if (left.type && left.type->cmp_eq)
557 return left.type->cmp_eq(left, right);
561 static void print_value(struct value v)
563 if (v.type && v.type->print)
566 printf("*Unknown*"); // NOTEST
569 static struct value parse_value(struct type *type, char *arg)
573 if (type && type->parse)
574 return type->parse(type, arg);
575 rv.type = NULL; // NOTEST
581 static void free_value(struct value v);
582 static int type_compat(struct type *require, struct type *have, int rules);
583 static void type_print(struct type *type, FILE *f);
584 static struct value val_init(struct type *type);
585 static struct value dup_value(struct value v);
586 static int value_cmp(struct value left, struct value right);
587 static void print_value(struct value v);
588 static struct value parse_value(struct type *type, char *arg);
590 ###### free context types
592 while (context.typelist) {
593 struct type *t = context.typelist;
595 context.typelist = t->next;
603 Values of the base types can be numbers, which we represent as
604 multi-precision fractions, strings, Booleans and labels. When
605 analysing the program we also need to allow for places where no value
606 is meaningful (type `Tnone`) and where we don't know what type to
607 expect yet (type is `NULL`).
609 Values are never shared, they are always copied when used, and freed
610 when no longer needed.
612 When propagating type information around the program, we need to
613 determine if two types are compatible, where type `NULL` is compatible
614 with anything. There are two special cases with type compatibility,
615 both related to the Conditional Statement which will be described
616 later. In some cases a Boolean can be accepted as well as some other
617 primary type, and in others any type is acceptable except a label (`Vlabel`).
618 A separate function encoding these cases will simplify some code later.
620 When assigning command line arguments to variables, we need to be able
621 to parse each type from a string.
623 The distinction beteen "prepare" and "init" needs to be explained.
624 "init" sets up an initial value, such as "zero" or the empty string.
625 "prepare" simply prepares the data structure so that if "free" gets
626 called on it, it won't do something silly. Normally a value will be
627 stored after "prepare" but before "free", but this might not happen if
636 myLDLIBS := libnumber.o libstring.o -lgmp
637 LDLIBS := $(filter-out $(myLDLIBS),$(LDLIBS)) $(myLDLIBS)
639 ###### type union fields
640 enum vtype {Vnone, Vstr, Vnum, Vbool, Vlabel} vtype;
642 ###### value union fields
649 static void _free_value(struct value v)
651 switch (v.type->vtype) {
653 case Vstr: free(v.str.txt); break;
654 case Vnum: mpq_clear(v.num); break;
660 ###### value functions
662 static struct value _val_prepare(struct type *type)
667 switch(type->vtype) {
671 memset(&rv.num, 0, sizeof(rv.num));
687 static struct value _val_init(struct type *type)
692 switch(type->vtype) {
693 case Vnone: // NOTEST
696 mpq_init(rv.num); break;
698 rv.str.txt = malloc(1);
704 case Vlabel: // NOTEST
705 rv.label = NULL; // NOTEST
711 static struct value _dup_value(struct value v)
715 switch (rv.type->vtype) {
716 case Vnone: // NOTEST
726 mpq_set(rv.num, v.num);
729 rv.str.len = v.str.len;
730 rv.str.txt = malloc(rv.str.len);
731 memcpy(rv.str.txt, v.str.txt, v.str.len);
737 static int _value_cmp(struct value left, struct value right)
740 if (left.type != right.type)
741 return left.type - right.type; // NOTEST
742 switch (left.type->vtype) {
743 case Vlabel: cmp = left.label == right.label ? 0 : 1; break;
744 case Vnum: cmp = mpq_cmp(left.num, right.num); break;
745 case Vstr: cmp = text_cmp(left.str, right.str); break;
746 case Vbool: cmp = left.bool - right.bool; break;
747 case Vnone: cmp = 0; // NOTEST
752 static void _print_value(struct value v)
754 switch (v.type->vtype) {
755 case Vnone: // NOTEST
756 printf("*no-value*"); break; // NOTEST
757 case Vlabel: // NOTEST
758 printf("*label-%p*", v.label); break; // NOTEST
760 printf("%.*s", v.str.len, v.str.txt); break;
762 printf("%s", v.bool ? "True":"False"); break;
767 mpf_set_q(fl, v.num);
768 gmp_printf("%Fg", fl);
775 static struct value _parse_value(struct type *type, char *arg)
783 switch(type->vtype) {
784 case Vlabel: // NOTEST
785 case Vnone: // NOTEST
786 val.type = NULL; // NOTEST
789 val.str.len = strlen(arg);
790 val.str.txt = malloc(val.str.len);
791 memcpy(val.str.txt, arg, val.str.len);
798 tx.txt = arg; tx.len = strlen(tx.txt);
799 if (number_parse(val.num, tail, tx) == 0)
802 mpq_neg(val.num, val.num);
804 printf("Unsupported suffix: %s\n", arg);
809 if (strcasecmp(arg, "true") == 0 ||
810 strcmp(arg, "1") == 0)
812 else if (strcasecmp(arg, "false") == 0 ||
813 strcmp(arg, "0") == 0)
816 printf("Bad bool: %s\n", arg);
824 static void _free_value(struct value v);
826 static struct type base_prototype = {
828 .prepare = _val_prepare,
829 .parse = _parse_value,
830 .print = _print_value,
831 .cmp_order = _value_cmp,
832 .cmp_eq = _value_cmp,
837 static struct type *Tbool, *Tstr, *Tnum, *Tnone, *Tlabel;
840 static struct type *add_base_type(struct parse_context *c, char *n, enum vtype vt)
842 struct text txt = { n, strlen(n) };
845 t = add_type(c, txt, &base_prototype);
850 ###### context initialization
852 Tbool = add_base_type(&context, "Boolean", Vbool);
853 Tstr = add_base_type(&context, "string", Vstr);
854 Tnum = add_base_type(&context, "number", Vnum);
855 Tnone = add_base_type(&context, "none", Vnone);
856 Tlabel = add_base_type(&context, "label", Vlabel);
860 Variables are scoped named values. We store the names in a linked
861 list of "bindings" sorted lexically, and use sequential search and
868 struct binding *next; // in lexical order
872 This linked list is stored in the parse context so that "reduce"
873 functions can find or add variables, and so the analysis phase can
874 ensure that every variable gets a type.
878 struct binding *varlist; // In lexical order
882 static struct binding *find_binding(struct parse_context *c, struct text s)
884 struct binding **l = &c->varlist;
889 (cmp = text_cmp((*l)->name, s)) < 0)
893 n = calloc(1, sizeof(*n));
900 Each name can be linked to multiple variables defined in different
901 scopes. Each scope starts where the name is declared and continues
902 until the end of the containing code block. Scopes of a given name
903 cannot nest, so a declaration while a name is in-scope is an error.
905 ###### binding fields
906 struct variable *var;
910 struct variable *previous;
912 struct binding *name;
913 struct exec *where_decl;// where name was declared
914 struct exec *where_set; // where type was set
918 While the naming seems strange, we include local constants in the
919 definition of variables. A name declared `var := value` can
920 subsequently be changed, but a name declared `var ::= value` cannot -
923 ###### variable fields
926 Scopes in parallel branches can be partially merged. More
927 specifically, if a given name is declared in both branches of an
928 if/else then its scope is a candidate for merging. Similarly if
929 every branch of an exhaustive switch (e.g. has an "else" clause)
930 declares a given name, then the scopes from the branches are
931 candidates for merging.
933 Note that names declared inside a loop (which is only parallel to
934 itself) are never visible after the loop. Similarly names defined in
935 scopes which are not parallel, such as those started by `for` and
936 `switch`, are never visible after the scope. Only variables defined in
937 both `then` and `else` (including the implicit then after an `if`, and
938 excluding `then` used with `for`) and in all `case`s and `else` of a
939 `switch` or `while` can be visible beyond the `if`/`switch`/`while`.
941 Labels, which are a bit like variables, follow different rules.
942 Labels are not explicitly declared, but if an undeclared name appears
943 in a context where a label is legal, that effectively declares the
944 name as a label. The declaration remains in force (or in scope) at
945 least to the end of the immediately containing block and conditionally
946 in any larger containing block which does not declare the name in some
947 other way. Importantly, the conditional scope extension happens even
948 if the label is only used in one parallel branch of a conditional --
949 when used in one branch it is treated as having been declared in all
952 Merge candidates are tentatively visible beyond the end of the
953 branching statement which creates them. If the name is used, the
954 merge is affirmed and they become a single variable visible at the
955 outer layer. If not - if it is redeclared first - the merge lapses.
957 To track scopes we have an extra stack, implemented as a linked list,
958 which roughly parallels the parse stack and which is used exclusively
959 for scoping. When a new scope is opened, a new frame is pushed and
960 the child-count of the parent frame is incremented. This child-count
961 is used to distinguish between the first of a set of parallel scopes,
962 in which declared variables must not be in scope, and subsequent
963 branches, whether they must already be conditionally scoped.
965 To push a new frame *before* any code in the frame is parsed, we need a
966 grammar reduction. This is most easily achieved with a grammar
967 element which derives the empty string, and creates the new scope when
968 it is recognized. This can be placed, for example, between a keyword
969 like "if" and the code following it.
973 struct scope *parent;
979 struct scope *scope_stack;
982 static void scope_pop(struct parse_context *c)
984 struct scope *s = c->scope_stack;
986 c->scope_stack = s->parent;
991 static void scope_push(struct parse_context *c)
993 struct scope *s = calloc(1, sizeof(*s));
995 c->scope_stack->child_count += 1;
996 s->parent = c->scope_stack;
1004 OpenScope -> ${ scope_push(config2context(config)); }$
1006 Each variable records a scope depth and is in one of four states:
1008 - "in scope". This is the case between the declaration of the
1009 variable and the end of the containing block, and also between
1010 the usage with affirms a merge and the end of that block.
1012 The scope depth is not greater than the current parse context scope
1013 nest depth. When the block of that depth closes, the state will
1014 change. To achieve this, all "in scope" variables are linked
1015 together as a stack in nesting order.
1017 - "pending". The "in scope" block has closed, but other parallel
1018 scopes are still being processed. So far, every parallel block at
1019 the same level that has closed has declared the name.
1021 The scope depth is the depth of the last parallel block that
1022 enclosed the declaration, and that has closed.
1024 - "conditionally in scope". The "in scope" block and all parallel
1025 scopes have closed, and no further mention of the name has been
1026 seen. This state includes a secondary nest depth which records the
1027 outermost scope seen since the variable became conditionally in
1028 scope. If a use of the name is found, the variable becomes "in
1029 scope" and that secondary depth becomes the recorded scope depth.
1030 If the name is declared as a new variable, the old variable becomes
1031 "out of scope" and the recorded scope depth stays unchanged.
1033 - "out of scope". The variable is neither in scope nor conditionally
1034 in scope. It is permanently out of scope now and can be removed from
1035 the "in scope" stack.
1038 ###### variable fields
1039 int depth, min_depth;
1040 enum { OutScope, PendingScope, CondScope, InScope } scope;
1041 struct variable *in_scope;
1043 ###### parse context
1045 struct variable *in_scope;
1047 All variables with the same name are linked together using the
1048 'previous' link. Those variable that have
1049 been affirmatively merged all have a 'merged' pointer that points to
1050 one primary variable - the most recently declared instance. When
1051 merging variables, we need to also adjust the 'merged' pointer on any
1052 other variables that had previously been merged with the one that will
1053 no longer be primary.
1055 A variable that is no longer the most recent instance of a name may
1056 still have "pending" scope, if it might still be merged with most
1057 recent instance. These variables don't really belong in the
1058 "in_scope" list, but are not immediately removed when a new instance
1059 is found. Instead, they are detected and ignored when considering the
1060 list of in_scope names.
1062 ###### variable fields
1063 struct variable *merged;
1065 ###### ast functions
1067 static void variable_merge(struct variable *primary, struct variable *secondary)
1071 if (primary->merged)
1073 primary = primary->merged;
1075 for (v = primary->previous; v; v=v->previous)
1076 if (v == secondary || v == secondary->merged ||
1077 v->merged == secondary ||
1078 (v->merged && v->merged == secondary->merged)) {
1079 v->scope = OutScope;
1080 v->merged = primary;
1084 ###### free context vars
1086 while (context.varlist) {
1087 struct binding *b = context.varlist;
1088 struct variable *v = b->var;
1089 context.varlist = b->next;
1092 struct variable *t = v;
1096 if (t->min_depth == 0)
1097 // This is a global constant
1098 free_exec(t->where_decl);
1103 #### Manipulating Bindings
1105 When a name is conditionally visible, a new declaration discards the
1106 old binding - the condition lapses. Conversely a usage of the name
1107 affirms the visibility and extends it to the end of the containing
1108 block - i.e. the block that contains both the original declaration and
1109 the latest usage. This is determined from `min_depth`. When a
1110 conditionally visible variable gets affirmed like this, it is also
1111 merged with other conditionally visible variables with the same name.
1113 When we parse a variable declaration we either report an error if the
1114 name is currently bound, or create a new variable at the current nest
1115 depth if the name is unbound or bound to a conditionally scoped or
1116 pending-scope variable. If the previous variable was conditionally
1117 scoped, it and its homonyms becomes out-of-scope.
1119 When we parse a variable reference (including non-declarative
1120 assignment) we report an error if the name is not bound or is bound to
1121 a pending-scope variable; update the scope if the name is bound to a
1122 conditionally scoped variable; or just proceed normally if the named
1123 variable is in scope.
1125 When we exit a scope, any variables bound at this level are either
1126 marked out of scope or pending-scoped, depending on whether the scope
1127 was sequential or parallel. Here a "parallel" scope means the "then"
1128 or "else" part of a conditional, or any "case" or "else" branch of a
1129 switch. Other scopes are "sequential".
1131 When exiting a parallel scope we check if there are any variables that
1132 were previously pending and are still visible. If there are, then
1133 there weren't redeclared in the most recent scope, so they cannot be
1134 merged and must become out-of-scope. If it is not the first of
1135 parallel scopes (based on `child_count`), we check that there was a
1136 previous binding that is still pending-scope. If there isn't, the new
1137 variable must now be out-of-scope.
1139 When exiting a sequential scope that immediately enclosed parallel
1140 scopes, we need to resolve any pending-scope variables. If there was
1141 no `else` clause, and we cannot determine that the `switch` was exhaustive,
1142 we need to mark all pending-scope variable as out-of-scope. Otherwise
1143 all pending-scope variables become conditionally scoped.
1146 enum closetype { CloseSequential, CloseParallel, CloseElse };
1148 ###### ast functions
1150 static struct variable *var_decl(struct parse_context *c, struct text s)
1152 struct binding *b = find_binding(c, s);
1153 struct variable *v = b->var;
1155 switch (v ? v->scope : OutScope) {
1157 /* Caller will report the error */
1161 v && v->scope == CondScope;
1163 v->scope = OutScope;
1167 v = calloc(1, sizeof(*v));
1168 v->previous = b->var;
1171 v->min_depth = v->depth = c->scope_depth;
1173 v->in_scope = c->in_scope;
1175 v->val = val_prepare(NULL);
1179 static struct variable *var_ref(struct parse_context *c, struct text s)
1181 struct binding *b = find_binding(c, s);
1182 struct variable *v = b->var;
1183 struct variable *v2;
1185 switch (v ? v->scope : OutScope) {
1188 /* Caller will report the error */
1191 /* All CondScope variables of this name need to be merged
1192 * and become InScope
1194 v->depth = v->min_depth;
1196 for (v2 = v->previous;
1197 v2 && v2->scope == CondScope;
1199 variable_merge(v, v2);
1207 static void var_block_close(struct parse_context *c, enum closetype ct)
1209 /* Close off all variables that are in_scope */
1210 struct variable *v, **vp, *v2;
1213 for (vp = &c->in_scope;
1214 v = *vp, v && v->depth > c->scope_depth && v->min_depth > c->scope_depth;
1216 if (v->name->var == v) switch (ct) {
1218 case CloseParallel: /* handle PendingScope */
1222 if (c->scope_stack->child_count == 1)
1223 v->scope = PendingScope;
1224 else if (v->previous &&
1225 v->previous->scope == PendingScope)
1226 v->scope = PendingScope;
1227 else if (v->val.type == Tlabel)
1228 v->scope = PendingScope;
1229 else if (v->name->var == v)
1230 v->scope = OutScope;
1231 if (ct == CloseElse) {
1232 /* All Pending variables with this name
1233 * are now Conditional */
1235 v2 && v2->scope == PendingScope;
1237 v2->scope = CondScope;
1242 v2 && v2->scope == PendingScope;
1244 if (v2->val.type != Tlabel)
1245 v2->scope = OutScope;
1247 case OutScope: break;
1250 case CloseSequential:
1251 if (v->val.type == Tlabel)
1252 v->scope = PendingScope;
1255 v->scope = OutScope;
1258 /* There was no 'else', so we can only become
1259 * conditional if we know the cases were exhaustive,
1260 * and that doesn't mean anything yet.
1261 * So only labels become conditional..
1264 v2 && v2->scope == PendingScope;
1266 if (v2->val.type == Tlabel) {
1267 v2->scope = CondScope;
1268 v2->min_depth = c->scope_depth;
1270 v2->scope = OutScope;
1273 case OutScope: break;
1277 if (v->scope == OutScope || v->name->var != v)
1286 Executables can be lots of different things. In many cases an
1287 executable is just an operation combined with one or two other
1288 executables. This allows for expressions and lists etc. Other times
1289 an executable is something quite specific like a constant or variable
1290 name. So we define a `struct exec` to be a general executable with a
1291 type, and a `struct binode` which is a subclass of `exec`, forms a
1292 node in a binary tree, and holds an operation. There will be other
1293 subclasses, and to access these we need to be able to `cast` the
1294 `exec` into the various other types.
1297 #define cast(structname, pointer) ({ \
1298 const typeof( ((struct structname *)0)->type) *__mptr = &(pointer)->type; \
1299 if (__mptr && *__mptr != X##structname) abort(); \
1300 (struct structname *)( (char *)__mptr);})
1302 #define new(structname) ({ \
1303 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1304 __ptr->type = X##structname; \
1305 __ptr->line = -1; __ptr->column = -1; \
1308 #define new_pos(structname, token) ({ \
1309 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1310 __ptr->type = X##structname; \
1311 __ptr->line = token.line; __ptr->column = token.col; \
1320 enum exec_types type;
1328 struct exec *left, *right;
1331 ###### ast functions
1333 static int __fput_loc(struct exec *loc, FILE *f)
1337 if (loc->line >= 0) {
1338 fprintf(f, "%d:%d: ", loc->line, loc->column);
1341 if (loc->type == Xbinode)
1342 return __fput_loc(cast(binode,loc)->left, f) ||
1343 __fput_loc(cast(binode,loc)->right, f);
1346 static void fput_loc(struct exec *loc, FILE *f)
1348 if (!__fput_loc(loc, f))
1349 fprintf(f, "??:??: "); // NOTEST
1352 Each different type of `exec` node needs a number of functions
1353 defined, a bit like methods. We must be able to be able to free it,
1354 print it, analyse it and execute it. Once we have specific `exec`
1355 types we will need to parse them too. Let's take this a bit more
1360 The parser generator requires a `free_foo` function for each struct
1361 that stores attributes and they will often be `exec`s and subtypes
1362 there-of. So we need `free_exec` which can handle all the subtypes,
1363 and we need `free_binode`.
1365 ###### ast functions
1367 static void free_binode(struct binode *b)
1372 free_exec(b->right);
1376 ###### core functions
1377 static void free_exec(struct exec *e)
1386 ###### forward decls
1388 static void free_exec(struct exec *e);
1390 ###### free exec cases
1391 case Xbinode: free_binode(cast(binode, e)); break;
1395 Printing an `exec` requires that we know the current indent level for
1396 printing line-oriented components. As will become clear later, we
1397 also want to know what sort of bracketing to use.
1399 ###### ast functions
1401 static void do_indent(int i, char *str)
1408 ###### core functions
1409 static void print_binode(struct binode *b, int indent, int bracket)
1413 ## print binode cases
1417 static void print_exec(struct exec *e, int indent, int bracket)
1423 print_binode(cast(binode, e), indent, bracket); break;
1428 ###### forward decls
1430 static void print_exec(struct exec *e, int indent, int bracket);
1434 As discussed, analysis involves propagating type requirements around
1435 the program and looking for errors.
1437 So `propagate_types` is passed an expected type (being a `struct type`
1438 pointer together with some `val_rules` flags) that the `exec` is
1439 expected to return, and returns the type that it does return, either
1440 of which can be `NULL` signifying "unknown". An `ok` flag is passed
1441 by reference. It is set to `0` when an error is found, and `2` when
1442 any change is made. If it remains unchanged at `1`, then no more
1443 propagation is needed.
1447 enum val_rules {Rnolabel = 1<<0, Rboolok = 1<<1, Rnoconstant = 2<<1};
1451 if (rules & Rnolabel)
1452 fputs(" (labels not permitted)", stderr);
1455 ###### core functions
1457 static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1458 struct type *type, int rules)
1465 switch (prog->type) {
1468 struct binode *b = cast(binode, prog);
1470 ## propagate binode cases
1474 ## propagate exec cases
1481 Interpreting an `exec` doesn't require anything but the `exec`. State
1482 is stored in variables and each variable will be directly linked from
1483 within the `exec` tree. The exception to this is the whole `program`
1484 which needs to look at command line arguments. The `program` will be
1485 interpreted separately.
1487 Each `exec` can return a value, which may be `Tnone` but must be
1488 non-NULL; Some `exec`s will return the location of a value, which can
1489 be updates. To support this, each exec case must store either a value
1490 in `val` or the pointer to a value in `lval`. If `lval` is set, but a
1491 simple value is required, `inter_exec()` will dereference `lval` to
1495 ###### core functions
1498 struct value val, *lval;
1501 static struct lrval _interp_exec(struct exec *e);
1503 static struct value interp_exec(struct exec *e)
1505 struct lrval ret = _interp_exec(e);
1508 return dup_value(*ret.lval);
1513 static struct value *linterp_exec(struct exec *e)
1515 struct lrval ret = _interp_exec(e);
1520 static struct lrval _interp_exec(struct exec *e)
1523 struct value rv, *lrv = NULL;
1534 struct binode *b = cast(binode, e);
1535 struct value left, right, *lleft;
1536 left.type = right.type = Tnone;
1538 ## interp binode cases
1540 free_value(left); free_value(right);
1543 ## interp exec cases
1552 Now that we have the shape of the interpreter in place we can add some
1553 complex types and connected them in to the data structures and the
1554 different phases of parse, analyse, print, interpret.
1556 Thus far we have arrays and structs.
1560 Arrays can be declared by giving a size and a type, as `[size]type' so
1561 `freq:[26]number` declares `freq` to be an array of 26 numbers. The
1562 size can be an arbitrary expression which is evaluated when the name
1565 Arrays cannot be assigned. When pointers are introduced we will also
1566 introduce array slices which can refer to part or all of an array -
1567 the assignment syntax will create a slice. For now, an array can only
1568 ever be referenced by the name it is declared with. It is likely that
1569 a "`copy`" primitive will eventually be define which can be used to
1570 make a copy of an array with controllable depth.
1572 ###### type union fields
1576 struct variable *vsize;
1577 struct type *member;
1580 ###### value union fields
1582 struct value *elmnts;
1585 ###### value functions
1587 static struct value array_prepare(struct type *type)
1592 ret.array.elmnts = NULL;
1596 static struct value array_init(struct type *type)
1602 if (type->array.vsize) {
1605 mpz_tdiv_q(q, mpq_numref(type->array.vsize->val.num),
1606 mpq_denref(type->array.vsize->val.num));
1607 type->array.size = mpz_get_si(q);
1610 ret.array.elmnts = calloc(type->array.size,
1611 sizeof(ret.array.elmnts[0]));
1612 for (i = 0; ret.array.elmnts && i < type->array.size; i++)
1613 ret.array.elmnts[i] = val_init(type->array.member);
1617 static void array_free(struct value val)
1621 if (val.array.elmnts)
1622 for (i = 0; i < val.type->array.size; i++)
1623 free_value(val.array.elmnts[i]);
1624 free(val.array.elmnts);
1627 static int array_compat(struct type *require, struct type *have)
1629 if (have->compat != require->compat)
1631 /* Both are arrays, so we can look at details */
1632 if (!type_compat(require->array.member, have->array.member, 0))
1634 if (require->array.vsize == NULL && have->array.vsize == NULL)
1635 return require->array.size == have->array.size;
1637 return require->array.vsize == have->array.vsize;
1640 static void array_print_type(struct type *type, FILE *f)
1643 if (type->array.vsize) {
1644 struct binding *b = type->array.vsize->name;
1645 fprintf(f, "%.*s]", b->name.len, b->name.txt);
1647 fprintf(f, "%d]", type->array.size);
1648 type_print(type->array.member, f);
1651 static struct type array_prototype = {
1652 .prepare = array_prepare,
1654 .print_type = array_print_type,
1655 .compat = array_compat,
1661 | [ NUMBER ] Type ${
1662 $0 = calloc(1, sizeof(struct type));
1663 *($0) = array_prototype;
1664 $0->array.member = $<4;
1665 $0->array.vsize = NULL;
1667 struct parse_context *c = config2context(config);
1670 if (number_parse(num, tail, $2.txt) == 0)
1671 tok_err(c, "error: unrecognised number", &$2);
1673 tok_err(c, "error: unsupported number suffix", &$2);
1675 $0->array.size = mpz_get_ui(mpq_numref(num));
1676 if (mpz_cmp_ui(mpq_denref(num), 1) != 0) {
1677 tok_err(c, "error: array size must be an integer",
1679 } else if (mpz_cmp_ui(mpq_numref(num), 1UL << 30) >= 0)
1680 tok_err(c, "error: array size is too large",
1684 $0->next= c->anon_typelist;
1685 c->anon_typelist = $0;
1689 | [ IDENTIFIER ] Type ${ {
1690 struct parse_context *c = config2context(config);
1691 struct variable *v = var_ref(c, $2.txt);
1694 tok_err(config2context(config), "error: name undeclared", &$2);
1695 else if (!v->constant)
1696 tok_err(config2context(config), "error: array size must be a constant", &$2);
1698 $0 = calloc(1, sizeof(struct type));
1699 *($0) = array_prototype;
1700 $0->array.member = $<4;
1702 $0->array.vsize = v;
1703 $0->next= c->anon_typelist;
1704 c->anon_typelist = $0;
1707 ###### parse context
1709 struct type *anon_typelist;
1711 ###### free context types
1713 while (context.anon_typelist) {
1714 struct type *t = context.anon_typelist;
1716 context.anon_typelist = t->next;
1723 ###### variable grammar
1725 | Variable [ Expression ] ${ {
1726 struct binode *b = new(binode);
1733 ###### print binode cases
1735 print_exec(b->left, -1, 0);
1737 print_exec(b->right, -1, 0);
1741 ###### propagate binode cases
1743 /* left must be an array, right must be a number,
1744 * result is the member type of the array
1746 propagate_types(b->right, c, ok, Tnum, 0);
1747 t = propagate_types(b->left, c, ok, NULL, rules & Rnoconstant);
1748 if (!t || t->compat != array_compat) {
1749 type_err(c, "error: %1 cannot be indexed", prog, t, 0, NULL);
1753 if (!type_compat(type, t->array.member, rules)) {
1754 type_err(c, "error: have %1 but need %2", prog,
1755 t->array.member, rules, type);
1758 return t->array.member;
1762 ###### interp binode cases
1767 lleft = linterp_exec(b->left);
1768 right = interp_exec(b->right);
1770 mpz_tdiv_q(q, mpq_numref(right.num), mpq_denref(right.num));
1774 if (i >= 0 && i < lleft->type->array.size)
1775 lrv = &lleft->array.elmnts[i];
1777 rv = val_init(lleft->type->array.member);
1783 A `struct` is a data-type that contains one or more other data-types.
1784 It differs from an array in that each member can be of a different
1785 type, and they are accessed by name rather than by number. Thus you
1786 cannot choose an element by calculation, you need to know what you
1789 The language makes no promises about how a given structure will be
1790 stored in memory - it is free to rearrange fields to suit whatever
1791 criteria seems important.
1793 Structs are declared separately from program code - they cannot be
1794 declared in-line in a variable declaration like arrays can. A struct
1795 is given a name and this name is used to identify the type - the name
1796 is not prefixed by the word `struct` as it would be in C.
1798 Structs are only treated as the same if they have the same name.
1799 Simply having the same fields in the same order is not enough. This
1800 might change once we can create structure initializes from a list of
1803 Each component datum is identified much like a variable is declared,
1804 with a name, one or two colons, and a type. The type cannot be omitted
1805 as there is no opportunity to deduce the type from usage. An initial
1806 value can be given following an equals sign, so
1808 ##### Example: a struct type
1814 would declare a type called "complex" which has two number fields,
1815 each initialised to zero.
1817 Struct will need to be declared separately from the code that uses
1818 them, so we will need to be able to print out the declaration of a
1819 struct when reprinting the whole program. So a `print_type_decl` type
1820 function will be needed.
1822 ###### type union fields
1833 ###### value union fields
1835 struct value *fields;
1838 ###### type functions
1839 void (*print_type_decl)(struct type *type, FILE *f);
1841 ###### value functions
1843 static struct value structure_prepare(struct type *type)
1848 ret.structure.fields = NULL;
1852 static struct value structure_init(struct type *type)
1858 ret.structure.fields = calloc(type->structure.nfields,
1859 sizeof(ret.structure.fields[0]));
1860 for (i = 0; ret.structure.fields && i < type->structure.nfields; i++)
1861 ret.structure.fields[i] = val_init(type->structure.fields[i].type);
1865 static void structure_free(struct value val)
1869 if (val.structure.fields)
1870 for (i = 0; i < val.type->structure.nfields; i++)
1871 free_value(val.structure.fields[i]);
1872 free(val.structure.fields);
1875 static void structure_free_type(struct type *t)
1878 for (i = 0; i < t->structure.nfields; i++)
1879 free_value(t->structure.fields[i].init);
1880 free(t->structure.fields);
1883 static struct type structure_prototype = {
1884 .prepare = structure_prepare,
1885 .init = structure_init,
1886 .free = structure_free,
1887 .free_type = structure_free_type,
1888 .print_type_decl = structure_print_type,
1902 ###### free exec cases
1904 free_exec(cast(fieldref, e)->left);
1908 ###### variable grammar
1910 | Variable . IDENTIFIER ${ {
1911 struct fieldref *fr = new_pos(fieldref, $2);
1918 ###### print exec cases
1922 struct fieldref *f = cast(fieldref, e);
1923 print_exec(f->left, -1, 0);
1924 printf(".%.*s", f->name.len, f->name.txt);
1928 ###### ast functions
1929 static int find_struct_index(struct type *type, struct text field)
1932 for (i = 0; i < type->structure.nfields; i++)
1933 if (text_cmp(type->structure.fields[i].name, field) == 0)
1938 ###### propagate exec cases
1942 struct fieldref *f = cast(fieldref, prog);
1943 struct type *st = propagate_types(f->left, c, ok, NULL, 0);
1946 type_err(c, "error: unknown type for field access", f->left,
1948 else if (st->prepare != structure_prepare)
1949 type_err(c, "error: field reference attempted on %1, not a struct",
1950 f->left, st, 0, NULL);
1951 else if (f->index == -2) {
1952 f->index = find_struct_index(st, f->name);
1954 type_err(c, "error: cannot find requested field in %1",
1955 f->left, st, 0, NULL);
1959 if (f->index >= 0) {
1960 struct type *ft = st->structure.fields[f->index].type;
1961 if (!type_compat(type, ft, rules)) {
1962 type_err(c, "error: have %1 but need %2", prog,
1971 ###### interp exec cases
1974 struct fieldref *f = cast(fieldref, e);
1975 struct value *lleft = linterp_exec(f->left);
1976 lrv = &lleft->structure.fields[f->index];
1982 struct fieldlist *prev;
1986 ###### ast functions
1987 static void free_fieldlist(struct fieldlist *f)
1991 free_fieldlist(f->prev);
1992 free_value(f->f.init);
1996 ###### top level grammar
1997 DeclareStruct -> struct IDENTIFIER FieldBlock ${ {
1999 add_type(config2context(config), $2.txt, &structure_prototype);
2001 struct fieldlist *f;
2003 for (f = $3; f; f=f->prev)
2006 t->structure.nfields = cnt;
2007 t->structure.fields = calloc(cnt, sizeof(struct field));
2011 t->structure.fields[cnt] = f->f;
2012 f->f.init = val_prepare(Tnone);
2018 FieldBlock -> Open SimpleFieldList Close ${ $0 = $<2; }$
2019 | Open Newlines SimpleFieldList Close ${ $0 = $<3; }$
2020 | : FieldList ${ $0 = $<2; }$
2022 FieldList -> Field NEWLINE ${ $0 = $<1; }$
2023 | FieldList NEWLINE ${ $0 = $<1; }$
2024 | FieldList Field NEWLINE ${
2029 SimpleFieldList -> Field ; ${ $0 = $<1; }$
2030 | SimpleFieldList Field ; ${
2035 Field -> IDENTIFIER : Type = Expression ${ {
2038 $0 = calloc(1, sizeof(struct fieldlist));
2039 $0->f.name = $1.txt;
2041 $0->f.init = val_prepare($0->f.type);
2044 propagate_types($<5, config2context(config), &ok, $3, 0);
2047 config2context(config)->parse_error = 1;
2049 $0->f.init = interp_exec($5);
2051 | IDENTIFIER : Type ${
2052 $0 = calloc(1, sizeof(struct fieldlist));
2053 $0->f.name = $1.txt;
2055 $0->f.init = val_init($3);
2058 ###### forward decls
2059 static void structure_print_type(struct type *t, FILE *f);
2061 ###### value functions
2062 static void structure_print_type(struct type *t, FILE *f)
2066 fprintf(f, "struct %.*s:\n", t->name.len, t->name.txt);
2068 for (i = 0; i < t->structure.nfields; i++) {
2069 struct field *fl = t->structure.fields + i;
2070 fprintf(f, " %.*s : ", fl->name.len, fl->name.txt);
2071 type_print(fl->type, f);
2072 if (fl->init.type->print) {
2074 if (fl->init.type == Tstr)
2076 print_value(fl->init);
2077 if (fl->init.type == Tstr)
2084 ###### print type decls
2089 while (target != 0) {
2091 for (t = context.typelist; t ; t=t->next)
2092 if (t->print_type_decl) {
2101 t->print_type_decl(t, stdout);
2107 ## Executables: the elements of code
2109 Each code element needs to be parsed, printed, analysed,
2110 interpreted, and freed. There are several, so let's just start with
2111 the easy ones and work our way up.
2115 We have already met values as separate objects. When manifest
2116 constants appear in the program text, that must result in an executable
2117 which has a constant value. So the `val` structure embeds a value in
2133 $0 = new_pos(val, $1);
2134 $0->val.type = Tbool;
2138 $0 = new_pos(val, $1);
2139 $0->val.type = Tbool;
2143 $0 = new_pos(val, $1);
2144 $0->val.type = Tnum;
2147 if (number_parse($0->val.num, tail, $1.txt) == 0)
2148 mpq_init($0->val.num);
2150 tok_err(config2context(config), "error: unsupported number suffix",
2155 $0 = new_pos(val, $1);
2156 $0->val.type = Tstr;
2159 string_parse(&$1, '\\', &$0->val.str, tail);
2161 tok_err(config2context(config), "error: unsupported string suffix",
2166 $0 = new_pos(val, $1);
2167 $0->val.type = Tstr;
2170 string_parse(&$1, '\\', &$0->val.str, tail);
2172 tok_err(config2context(config), "error: unsupported string suffix",
2177 ###### print exec cases
2180 struct val *v = cast(val, e);
2181 if (v->val.type == Tstr)
2183 print_value(v->val);
2184 if (v->val.type == Tstr)
2189 ###### propagate exec cases
2192 struct val *val = cast(val, prog);
2193 if (!type_compat(type, val->val.type, rules)) {
2194 type_err(c, "error: expected %1%r found %2",
2195 prog, type, rules, val->val.type);
2198 return val->val.type;
2201 ###### interp exec cases
2203 rv = dup_value(cast(val, e)->val);
2206 ###### ast functions
2207 static void free_val(struct val *v)
2215 ###### free exec cases
2216 case Xval: free_val(cast(val, e)); break;
2218 ###### ast functions
2219 // Move all nodes from 'b' to 'rv', reversing the order.
2220 // In 'b' 'left' is a list, and 'right' is the last node.
2221 // In 'rv', left' is the first node and 'right' is a list.
2222 static struct binode *reorder_bilist(struct binode *b)
2224 struct binode *rv = NULL;
2227 struct exec *t = b->right;
2231 b = cast(binode, b->left);
2241 Just as we used a `val` to wrap a value into an `exec`, we similarly
2242 need a `var` to wrap a `variable` into an exec. While each `val`
2243 contained a copy of the value, each `var` hold a link to the variable
2244 because it really is the same variable no matter where it appears.
2245 When a variable is used, we need to remember to follow the `->merged`
2246 link to find the primary instance.
2254 struct variable *var;
2260 VariableDecl -> IDENTIFIER : ${ {
2261 struct variable *v = var_decl(config2context(config), $1.txt);
2262 $0 = new_pos(var, $1);
2267 v = var_ref(config2context(config), $1.txt);
2269 type_err(config2context(config), "error: variable '%v' redeclared",
2271 type_err(config2context(config), "info: this is where '%v' was first declared",
2272 v->where_decl, NULL, 0, NULL);
2275 | IDENTIFIER :: ${ {
2276 struct variable *v = var_decl(config2context(config), $1.txt);
2277 $0 = new_pos(var, $1);
2283 v = var_ref(config2context(config), $1.txt);
2285 type_err(config2context(config), "error: variable '%v' redeclared",
2287 type_err(config2context(config), "info: this is where '%v' was first declared",
2288 v->where_decl, NULL, 0, NULL);
2291 | IDENTIFIER : Type ${ {
2292 struct variable *v = var_decl(config2context(config), $1.txt);
2293 $0 = new_pos(var, $1);
2298 v->val = val_prepare($<3);
2300 v = var_ref(config2context(config), $1.txt);
2302 type_err(config2context(config), "error: variable '%v' redeclared",
2304 type_err(config2context(config), "info: this is where '%v' was first declared",
2305 v->where_decl, NULL, 0, NULL);
2308 | IDENTIFIER :: Type ${ {
2309 struct variable *v = var_decl(config2context(config), $1.txt);
2310 $0 = new_pos(var, $1);
2315 v->val = val_prepare($<3);
2318 v = var_ref(config2context(config), $1.txt);
2320 type_err(config2context(config), "error: variable '%v' redeclared",
2322 type_err(config2context(config), "info: this is where '%v' was first declared",
2323 v->where_decl, NULL, 0, NULL);
2328 Variable -> IDENTIFIER ${ {
2329 struct variable *v = var_ref(config2context(config), $1.txt);
2330 $0 = new_pos(var, $1);
2332 /* This might be a label - allocate a var just in case */
2333 v = var_decl(config2context(config), $1.txt);
2335 v->val = val_prepare(Tlabel);
2336 v->val.label = &v->val;
2340 cast(var, $0)->var = v;
2345 Type -> IDENTIFIER ${
2346 $0 = find_type(config2context(config), $1.txt);
2348 tok_err(config2context(config),
2349 "error: undefined type", &$1);
2356 ###### print exec cases
2359 struct var *v = cast(var, e);
2361 struct binding *b = v->var->name;
2362 printf("%.*s", b->name.len, b->name.txt);
2369 if (loc->type == Xvar) {
2370 struct var *v = cast(var, loc);
2372 struct binding *b = v->var->name;
2373 fprintf(stderr, "%.*s", b->name.len, b->name.txt);
2375 fputs("???", stderr); // NOTEST
2377 fputs("NOTVAR", stderr); // NOTEST
2380 ###### propagate exec cases
2384 struct var *var = cast(var, prog);
2385 struct variable *v = var->var;
2387 type_err(c, "%d:BUG: no variable!!", prog, NULL, 0, NULL); // NOTEST
2389 return Tnone; // NOTEST
2393 if (v->constant && (rules & Rnoconstant)) {
2394 type_err(c, "error: Cannot assign to a constant: %v",
2395 prog, NULL, 0, NULL);
2396 type_err(c, "info: name was defined as a constant here",
2397 v->where_decl, NULL, 0, NULL);
2401 if (v->val.type == NULL) {
2402 if (type && *ok != 0) {
2403 v->val = val_prepare(type);
2404 v->where_set = prog;
2409 if (!type_compat(type, v->val.type, rules)) {
2410 type_err(c, "error: expected %1%r but variable '%v' is %2", prog,
2411 type, rules, v->val.type);
2412 type_err(c, "info: this is where '%v' was set to %1", v->where_set,
2413 v->val.type, rules, NULL);
2421 ###### interp exec cases
2424 struct var *var = cast(var, e);
2425 struct variable *v = var->var;
2433 ###### ast functions
2435 static void free_var(struct var *v)
2440 ###### free exec cases
2441 case Xvar: free_var(cast(var, e)); break;
2443 ### Expressions: Conditional
2445 Our first user of the `binode` will be conditional expressions, which
2446 is a bit odd as they actually have three components. That will be
2447 handled by having 2 binodes for each expression. The conditional
2448 expression is the lowest precedence operatior, so it gets to define
2449 what an "Expression" is. The next level up is "BoolExpr", which
2452 Conditional expressions are of the form "value `if` condition `else`
2453 other_value". They associate to the right, so everything to the right
2454 of `else` is part of an else value, while only the BoolExpr to the
2455 left of `if` is the if values. Between `if` and `else` there is no
2456 room for ambiguity, so a full conditional expression is allowed in there.
2464 Expression -> BoolExpr if Expression else Expression ${ {
2465 struct binode *b1 = new(binode);
2466 struct binode *b2 = new(binode);
2475 | BoolExpr ${ $0 = $<1; }$
2477 ###### print binode cases
2480 b2 = cast(binode, b->right);
2481 print_exec(b2->left, -1, 0);
2483 print_exec(b->left, -1, 0);
2485 print_exec(b2->right, -1, 0);
2488 ###### propagate binode cases
2491 /* cond must be Tbool, others must match */
2492 struct binode *b2 = cast(binode, b->right);
2495 propagate_types(b->left, c, ok, Tbool, 0);
2496 t = propagate_types(b2->left, c, ok, type, Rnolabel);
2497 t2 = propagate_types(b2->right, c, ok, type ?: t, Rnolabel);
2501 ###### interp binode cases
2504 struct binode *b2 = cast(binode, b->right);
2505 left = interp_exec(b->left);
2507 rv = interp_exec(b2->left);
2509 rv = interp_exec(b2->right);
2513 ### Expressions: Boolean
2515 The next class of expressions to use the `binode` will be Boolean
2516 expressions. As I haven't implemented precedence in the parser
2517 generator yet, we need different names for each precedence level used
2518 by expressions. The outer most or lowest level precedence after
2519 conditional expressions are Boolean operators which form an `BoolExpr`
2520 out of `BTerm`s and `BFact`s. As well as `or` `and`, and `not` we
2521 have `and then` and `or else` which only evaluate the second operand
2522 if the result would make a difference.
2534 BoolExpr -> BoolExpr or BTerm ${ {
2535 struct binode *b = new(binode);
2541 | BoolExpr or else BTerm ${ {
2542 struct binode *b = new(binode);
2548 | BTerm ${ $0 = $<1; }$
2550 BTerm -> BTerm and BFact ${ {
2551 struct binode *b = new(binode);
2557 | BTerm and then BFact ${ {
2558 struct binode *b = new(binode);
2564 | BFact ${ $0 = $<1; }$
2566 BFact -> not BFact ${ {
2567 struct binode *b = new(binode);
2574 ###### print binode cases
2576 print_exec(b->left, -1, 0);
2578 print_exec(b->right, -1, 0);
2581 print_exec(b->left, -1, 0);
2582 printf(" and then ");
2583 print_exec(b->right, -1, 0);
2586 print_exec(b->left, -1, 0);
2588 print_exec(b->right, -1, 0);
2591 print_exec(b->left, -1, 0);
2592 printf(" or else ");
2593 print_exec(b->right, -1, 0);
2597 print_exec(b->right, -1, 0);
2600 ###### propagate binode cases
2606 /* both must be Tbool, result is Tbool */
2607 propagate_types(b->left, c, ok, Tbool, 0);
2608 propagate_types(b->right, c, ok, Tbool, 0);
2609 if (type && type != Tbool) {
2610 type_err(c, "error: %1 operation found where %2 expected", prog,
2616 ###### interp binode cases
2618 rv = interp_exec(b->left);
2619 right = interp_exec(b->right);
2620 rv.bool = rv.bool && right.bool;
2623 rv = interp_exec(b->left);
2625 rv = interp_exec(b->right);
2628 rv = interp_exec(b->left);
2629 right = interp_exec(b->right);
2630 rv.bool = rv.bool || right.bool;
2633 rv = interp_exec(b->left);
2635 rv = interp_exec(b->right);
2638 rv = interp_exec(b->right);
2642 ### Expressions: Comparison
2644 Of slightly higher precedence that Boolean expressions are
2646 A comparison takes arguments of any comparable type, but the two types must be
2649 To simplify the parsing we introduce an `eop` which can record an
2650 expression operator.
2657 ###### ast functions
2658 static void free_eop(struct eop *e)
2673 | Expr CMPop Expr ${ {
2674 struct binode *b = new(binode);
2680 | Expr ${ $0 = $<1; }$
2685 CMPop -> < ${ $0.op = Less; }$
2686 | > ${ $0.op = Gtr; }$
2687 | <= ${ $0.op = LessEq; }$
2688 | >= ${ $0.op = GtrEq; }$
2689 | == ${ $0.op = Eql; }$
2690 | != ${ $0.op = NEql; }$
2692 ###### print binode cases
2700 print_exec(b->left, -1, 0);
2702 case Less: printf(" < "); break;
2703 case LessEq: printf(" <= "); break;
2704 case Gtr: printf(" > "); break;
2705 case GtrEq: printf(" >= "); break;
2706 case Eql: printf(" == "); break;
2707 case NEql: printf(" != "); break;
2708 default: abort(); // NOTEST
2710 print_exec(b->right, -1, 0);
2713 ###### propagate binode cases
2720 /* Both must match but not be labels, result is Tbool */
2721 t = propagate_types(b->left, c, ok, NULL, Rnolabel);
2723 propagate_types(b->right, c, ok, t, 0);
2725 t = propagate_types(b->right, c, ok, NULL, Rnolabel);
2727 t = propagate_types(b->left, c, ok, t, 0);
2729 if (!type_compat(type, Tbool, 0)) {
2730 type_err(c, "error: Comparison returns %1 but %2 expected", prog,
2731 Tbool, rules, type);
2736 ###### interp binode cases
2745 left = interp_exec(b->left);
2746 right = interp_exec(b->right);
2747 cmp = value_cmp(left, right);
2750 case Less: rv.bool = cmp < 0; break;
2751 case LessEq: rv.bool = cmp <= 0; break;
2752 case Gtr: rv.bool = cmp > 0; break;
2753 case GtrEq: rv.bool = cmp >= 0; break;
2754 case Eql: rv.bool = cmp == 0; break;
2755 case NEql: rv.bool = cmp != 0; break;
2756 default: rv.bool = 0; break; // NOTEST
2761 ### Expressions: The rest
2763 The remaining expressions with the highest precedence are arithmetic
2764 and string concatenation. They are `Expr`, `Term`, and `Factor`.
2765 The `Factor` is where the `Value` and `Variable` that we already have
2768 `+` and `-` are both infix and prefix operations (where they are
2769 absolute value and negation). These have different operator names.
2771 We also have a 'Bracket' operator which records where parentheses were
2772 found. This makes it easy to reproduce these when printing. Once
2773 precedence is handled better I might be able to discard this.
2785 Expr -> Expr Eop Term ${ {
2786 struct binode *b = new(binode);
2792 | Term ${ $0 = $<1; }$
2794 Term -> Term Top Factor ${ {
2795 struct binode *b = new(binode);
2801 | Factor ${ $0 = $<1; }$
2803 Factor -> ( Expression ) ${ {
2804 struct binode *b = new_pos(binode, $1);
2810 struct binode *b = new(binode);
2815 | Value ${ $0 = $<1; }$
2816 | Variable ${ $0 = $<1; }$
2819 Eop -> + ${ $0.op = Plus; }$
2820 | - ${ $0.op = Minus; }$
2822 Uop -> + ${ $0.op = Absolute; }$
2823 | - ${ $0.op = Negate; }$
2825 Top -> * ${ $0.op = Times; }$
2826 | / ${ $0.op = Divide; }$
2827 | % ${ $0.op = Rem; }$
2828 | ++ ${ $0.op = Concat; }$
2830 ###### print binode cases
2837 print_exec(b->left, indent, 0);
2839 case Plus: fputs(" + ", stdout); break;
2840 case Minus: fputs(" - ", stdout); break;
2841 case Times: fputs(" * ", stdout); break;
2842 case Divide: fputs(" / ", stdout); break;
2843 case Rem: fputs(" % ", stdout); break;
2844 case Concat: fputs(" ++ ", stdout); break;
2845 default: abort(); // NOTEST
2847 print_exec(b->right, indent, 0);
2851 print_exec(b->right, indent, 0);
2855 print_exec(b->right, indent, 0);
2859 print_exec(b->right, indent, 0);
2863 ###### propagate binode cases
2869 /* both must be numbers, result is Tnum */
2872 /* as propagate_types ignores a NULL,
2873 * unary ops fit here too */
2874 propagate_types(b->left, c, ok, Tnum, 0);
2875 propagate_types(b->right, c, ok, Tnum, 0);
2876 if (!type_compat(type, Tnum, 0)) {
2877 type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
2884 /* both must be Tstr, result is Tstr */
2885 propagate_types(b->left, c, ok, Tstr, 0);
2886 propagate_types(b->right, c, ok, Tstr, 0);
2887 if (!type_compat(type, Tstr, 0)) {
2888 type_err(c, "error: Concat returns %1 but %2 expected", prog,
2895 return propagate_types(b->right, c, ok, type, 0);
2897 ###### interp binode cases
2900 rv = interp_exec(b->left);
2901 right = interp_exec(b->right);
2902 mpq_add(rv.num, rv.num, right.num);
2905 rv = interp_exec(b->left);
2906 right = interp_exec(b->right);
2907 mpq_sub(rv.num, rv.num, right.num);
2910 rv = interp_exec(b->left);
2911 right = interp_exec(b->right);
2912 mpq_mul(rv.num, rv.num, right.num);
2915 rv = interp_exec(b->left);
2916 right = interp_exec(b->right);
2917 mpq_div(rv.num, rv.num, right.num);
2922 left = interp_exec(b->left);
2923 right = interp_exec(b->right);
2924 mpz_init(l); mpz_init(r); mpz_init(rem);
2925 mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
2926 mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
2927 mpz_tdiv_r(rem, l, r);
2928 rv = val_init(Tnum);
2929 mpq_set_z(rv.num, rem);
2930 mpz_clear(r); mpz_clear(l); mpz_clear(rem);
2934 rv = interp_exec(b->right);
2935 mpq_neg(rv.num, rv.num);
2938 rv = interp_exec(b->right);
2939 mpq_abs(rv.num, rv.num);
2942 rv = interp_exec(b->right);
2945 left = interp_exec(b->left);
2946 right = interp_exec(b->right);
2948 rv.str = text_join(left.str, right.str);
2952 ###### value functions
2954 static struct text text_join(struct text a, struct text b)
2957 rv.len = a.len + b.len;
2958 rv.txt = malloc(rv.len);
2959 memcpy(rv.txt, a.txt, a.len);
2960 memcpy(rv.txt+a.len, b.txt, b.len);
2964 ### Blocks, Statements, and Statement lists.
2966 Now that we have expressions out of the way we need to turn to
2967 statements. There are simple statements and more complex statements.
2968 Simple statements do not contain (syntactic) newlines, complex statements do.
2970 Statements often come in sequences and we have corresponding simple
2971 statement lists and complex statement lists.
2972 The former comprise only simple statements separated by semicolons.
2973 The later comprise complex statements and simple statement lists. They are
2974 separated by newlines. Thus the semicolon is only used to separate
2975 simple statements on the one line. This may be overly restrictive,
2976 but I'm not sure I ever want a complex statement to share a line with
2979 Note that a simple statement list can still use multiple lines if
2980 subsequent lines are indented, so
2982 ###### Example: wrapped simple statement list
2987 is a single simple statement list. This might allow room for
2988 confusion, so I'm not set on it yet.
2990 A simple statement list needs no extra syntax. A complex statement
2991 list has two syntactic forms. It can be enclosed in braces (much like
2992 C blocks), or it can be introduced by a colon and continue until an
2993 unindented newline (much like Python blocks). With this extra syntax
2994 it is referred to as a block.
2996 Note that a block does not have to include any newlines if it only
2997 contains simple statements. So both of:
2999 if condition: a=b; d=f
3001 if condition { a=b; print f }
3005 In either case the list is constructed from a `binode` list with
3006 `Block` as the operator. When parsing the list it is most convenient
3007 to append to the end, so a list is a list and a statement. When using
3008 the list it is more convenient to consider a list to be a statement
3009 and a list. So we need a function to re-order a list.
3010 `reorder_bilist` serves this purpose.
3012 The only stand-alone statement we introduce at this stage is `pass`
3013 which does nothing and is represented as a `NULL` pointer in a `Block`
3014 list. Other stand-alone statements will follow once the infrastructure
3034 Block -> Open Statementlist Close ${ $0 = $<2; }$
3035 | Open Newlines Statementlist Close ${ $0 = $<3; }$
3036 | Open SimpleStatements } ${ $0 = reorder_bilist($<2); }$
3037 | Open Newlines SimpleStatements } ${ $0 = reorder_bilist($<3); }$
3038 | : Statementlist ${ $0 = $<2; }$
3039 | : SimpleStatements ${ $0 = reorder_bilist($<2); }$
3041 Statementlist -> ComplexStatements ${ $0 = reorder_bilist($<1); }$
3043 ComplexStatements -> ComplexStatements ComplexStatement ${
3049 | ComplexStatements NEWLINE ${ $0 = $<1; }$
3050 | ComplexStatement ${
3058 ComplexStatement -> SimpleStatements NEWLINE ${
3059 $0 = reorder_bilist($<1);
3061 ## ComplexStatement Grammar
3064 SimpleStatements -> SimpleStatements ; SimpleStatement ${
3070 | SimpleStatement ${
3076 | SimpleStatements ; ${ $0 = $<1; }$
3078 SimpleStatement -> pass ${ $0 = NULL; }$
3079 ## SimpleStatement Grammar
3081 ###### print binode cases
3085 if (b->left == NULL)
3088 print_exec(b->left, indent, 0);
3091 print_exec(b->right, indent, 0);
3094 // block, one per line
3095 if (b->left == NULL)
3096 do_indent(indent, "pass\n");
3098 print_exec(b->left, indent, bracket);
3100 print_exec(b->right, indent, bracket);
3104 ###### propagate binode cases
3107 /* If any statement returns something other than Tnone
3108 * or Tbool then all such must return same type.
3109 * As each statement may be Tnone or something else,
3110 * we must always pass NULL (unknown) down, otherwise an incorrect
3111 * error might occur. We never return Tnone unless it is
3116 for (e = b; e; e = cast(binode, e->right)) {
3117 t = propagate_types(e->left, c, ok, NULL, rules);
3118 if ((rules & Rboolok) && t == Tbool)
3120 if (t && t != Tnone && t != Tbool) {
3123 else if (t != type) {
3124 type_err(c, "error: expected %1%r, found %2",
3125 e->left, type, rules, t);
3133 ###### interp binode cases
3135 while (rv.type == Tnone &&
3138 rv = interp_exec(b->left);
3139 b = cast(binode, b->right);
3143 ### The Print statement
3145 `print` is a simple statement that takes a comma-separated list of
3146 expressions and prints the values separated by spaces and terminated
3147 by a newline. No control of formatting is possible.
3149 `print` faces the same list-ordering issue as blocks, and uses the
3155 ###### SimpleStatement Grammar
3157 | print ExpressionList ${
3158 $0 = reorder_bilist($<2);
3160 | print ExpressionList , ${
3165 $0 = reorder_bilist($0);
3176 ExpressionList -> ExpressionList , Expression ${
3189 ###### print binode cases
3192 do_indent(indent, "print");
3196 print_exec(b->left, -1, 0);
3200 b = cast(binode, b->right);
3206 ###### propagate binode cases
3209 /* don't care but all must be consistent */
3210 propagate_types(b->left, c, ok, NULL, Rnolabel);
3211 propagate_types(b->right, c, ok, NULL, Rnolabel);
3214 ###### interp binode cases
3220 for ( ; b; b = cast(binode, b->right))
3224 left = interp_exec(b->left);
3237 ###### Assignment statement
3239 An assignment will assign a value to a variable, providing it hasn't
3240 be declared as a constant. The analysis phase ensures that the type
3241 will be correct so the interpreter just needs to perform the
3242 calculation. There is a form of assignment which declares a new
3243 variable as well as assigning a value. If a name is assigned before
3244 it is declared, and error will be raised as the name is created as
3245 `Tlabel` and it is illegal to assign to such names.
3251 ###### SimpleStatement Grammar
3252 | Variable = Expression ${
3258 | VariableDecl = Expression ${
3266 if ($1->var->where_set == NULL) {
3267 type_err(config2context(config),
3268 "Variable declared with no type or value: %v",
3278 ###### print binode cases
3281 do_indent(indent, "");
3282 print_exec(b->left, indent, 0);
3284 print_exec(b->right, indent, 0);
3291 struct variable *v = cast(var, b->left)->var;
3292 do_indent(indent, "");
3293 print_exec(b->left, indent, 0);
3294 if (cast(var, b->left)->var->constant) {
3295 if (v->where_decl == v->where_set) {
3297 type_print(v->val.type, stdout);
3302 if (v->where_decl == v->where_set) {
3304 type_print(v->val.type, stdout);
3311 print_exec(b->right, indent, 0);
3318 ###### propagate binode cases
3322 /* Both must match and not be labels,
3323 * Type must support 'dup',
3324 * For Assign, left must not be constant.
3327 t = propagate_types(b->left, c, ok, NULL,
3328 Rnolabel | (b->op == Assign ? Rnoconstant : 0));
3333 if (propagate_types(b->right, c, ok, t, 0) != t)
3334 if (b->left->type == Xvar)
3335 type_err(c, "info: variable '%v' was set as %1 here.",
3336 cast(var, b->left)->var->where_set, t, rules, NULL);
3338 t = propagate_types(b->right, c, ok, NULL, Rnolabel);
3340 propagate_types(b->left, c, ok, t,
3341 (b->op == Assign ? Rnoconstant : 0));
3343 if (t && t->dup == NULL) {
3344 type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
3351 ###### interp binode cases
3354 lleft = linterp_exec(b->left);
3355 right = interp_exec(b->right);
3360 free_value(right); // NOTEST
3366 struct variable *v = cast(var, b->left)->var;
3370 right = interp_exec(b->right);
3372 right = val_init(v->val.type);
3379 ### The `use` statement
3381 The `use` statement is the last "simple" statement. It is needed when
3382 the condition in a conditional statement is a block. `use` works much
3383 like `return` in C, but only completes the `condition`, not the whole
3389 ###### SimpleStatement Grammar
3391 $0 = new_pos(binode, $1);
3396 ###### print binode cases
3399 do_indent(indent, "use ");
3400 print_exec(b->right, -1, 0);
3405 ###### propagate binode cases
3408 /* result matches value */
3409 return propagate_types(b->right, c, ok, type, 0);
3411 ###### interp binode cases
3414 rv = interp_exec(b->right);
3417 ### The Conditional Statement
3419 This is the biggy and currently the only complex statement. This
3420 subsumes `if`, `while`, `do/while`, `switch`, and some parts of `for`.
3421 It is comprised of a number of parts, all of which are optional though
3422 set combinations apply. Each part is (usually) a key word (`then` is
3423 sometimes optional) followed by either an expression or a code block,
3424 except the `casepart` which is a "key word and an expression" followed
3425 by a code block. The code-block option is valid for all parts and,
3426 where an expression is also allowed, the code block can use the `use`
3427 statement to report a value. If the code block does not report a value
3428 the effect is similar to reporting `True`.
3430 The `else` and `case` parts, as well as `then` when combined with
3431 `if`, can contain a `use` statement which will apply to some
3432 containing conditional statement. `for` parts, `do` parts and `then`
3433 parts used with `for` can never contain a `use`, except in some
3434 subordinate conditional statement.
3436 If there is a `forpart`, it is executed first, only once.
3437 If there is a `dopart`, then it is executed repeatedly providing
3438 always that the `condpart` or `cond`, if present, does not return a non-True
3439 value. `condpart` can fail to return any value if it simply executes
3440 to completion. This is treated the same as returning `True`.
3442 If there is a `thenpart` it will be executed whenever the `condpart`
3443 or `cond` returns True (or does not return any value), but this will happen
3444 *after* `dopart` (when present).
3446 If `elsepart` is present it will be executed at most once when the
3447 condition returns `False` or some value that isn't `True` and isn't
3448 matched by any `casepart`. If there are any `casepart`s, they will be
3449 executed when the condition returns a matching value.
3451 The particular sorts of values allowed in case parts has not yet been
3452 determined in the language design, so nothing is prohibited.
3454 The various blocks in this complex statement potentially provide scope
3455 for variables as described earlier. Each such block must include the
3456 "OpenScope" nonterminal before parsing the block, and must call
3457 `var_block_close()` when closing the block.
3459 The code following "`if`", "`switch`" and "`for`" does not get its own
3460 scope, but is in a scope covering the whole statement, so names
3461 declared there cannot be redeclared elsewhere. Similarly the
3462 condition following "`while`" is in a scope the covers the body
3463 ("`do`" part) of the loop, and which does not allow conditional scope
3464 extension. Code following "`then`" (both looping and non-looping),
3465 "`else`" and "`case`" each get their own local scope.
3467 The type requirements on the code block in a `whilepart` are quite
3468 unusal. It is allowed to return a value of some identifiable type, in
3469 which case the loop aborts and an appropriate `casepart` is run, or it
3470 can return a Boolean, in which case the loop either continues to the
3471 `dopart` (on `True`) or aborts and runs the `elsepart` (on `False`).
3472 This is different both from the `ifpart` code block which is expected to
3473 return a Boolean, or the `switchpart` code block which is expected to
3474 return the same type as the casepart values. The correct analysis of
3475 the type of the `whilepart` code block is the reason for the
3476 `Rboolok` flag which is passed to `propagate_types()`.
3478 The `cond_statement` cannot fit into a `binode` so a new `exec` is
3487 struct exec *action;
3488 struct casepart *next;
3490 struct cond_statement {
3492 struct exec *forpart, *condpart, *dopart, *thenpart, *elsepart;
3493 struct casepart *casepart;
3496 ###### ast functions
3498 static void free_casepart(struct casepart *cp)
3502 free_exec(cp->value);
3503 free_exec(cp->action);
3510 static void free_cond_statement(struct cond_statement *s)
3514 free_exec(s->forpart);
3515 free_exec(s->condpart);
3516 free_exec(s->dopart);
3517 free_exec(s->thenpart);
3518 free_exec(s->elsepart);
3519 free_casepart(s->casepart);
3523 ###### free exec cases
3524 case Xcond_statement: free_cond_statement(cast(cond_statement, e)); break;
3526 ###### ComplexStatement Grammar
3527 | CondStatement ${ $0 = $<1; }$
3532 // both ForThen and Whilepart open scopes, and CondSuffix only
3533 // closes one - so in the first branch here we have another to close.
3534 CondStatement -> ForThen WhilePart CondSuffix ${
3536 $0->forpart = $1.forpart; $1.forpart = NULL;
3537 $0->thenpart = $1.thenpart; $1.thenpart = NULL;
3538 $0->condpart = $2.condpart; $2.condpart = NULL;
3539 $0->dopart = $2.dopart; $2.dopart = NULL;
3540 var_block_close(config2context(config), CloseSequential);
3542 | WhilePart CondSuffix ${
3544 $0->condpart = $1.condpart; $1.condpart = NULL;
3545 $0->dopart = $1.dopart; $1.dopart = NULL;
3547 | SwitchPart CondSuffix ${
3551 | IfPart IfSuffix ${
3553 $0->condpart = $1.condpart; $1.condpart = NULL;
3554 $0->thenpart = $1.thenpart; $1.thenpart = NULL;
3555 // This is where we close an "if" statement
3556 var_block_close(config2context(config), CloseSequential);
3559 CondSuffix -> IfSuffix ${
3561 // This is where we close scope of the whole
3562 // "for" or "while" statement
3563 var_block_close(config2context(config), CloseSequential);
3565 | CasePart CondSuffix ${
3567 $1->next = $0->casepart;
3572 CasePart -> Newlines case Expression OpenScope Block ${
3573 $0 = calloc(1,sizeof(struct casepart));
3576 var_block_close(config2context(config), CloseParallel);
3578 | case Expression OpenScope Block ${
3579 $0 = calloc(1,sizeof(struct casepart));
3582 var_block_close(config2context(config), CloseParallel);
3586 IfSuffix -> Newlines ${ $0 = new(cond_statement); }$
3587 | Newlines else OpenScope Block ${
3588 $0 = new(cond_statement);
3590 var_block_close(config2context(config), CloseElse);
3592 | else OpenScope Block ${
3593 $0 = new(cond_statement);
3595 var_block_close(config2context(config), CloseElse);
3597 | Newlines else OpenScope CondStatement ${
3598 $0 = new(cond_statement);
3600 var_block_close(config2context(config), CloseElse);
3602 | else OpenScope CondStatement ${
3603 $0 = new(cond_statement);
3605 var_block_close(config2context(config), CloseElse);
3610 // These scopes are closed in CondSuffix
3611 ForPart -> for OpenScope SimpleStatements ${
3612 $0 = reorder_bilist($<3);
3614 | for OpenScope Block ${
3618 ThenPart -> then OpenScope SimpleStatements ${
3619 $0 = reorder_bilist($<3);
3620 var_block_close(config2context(config), CloseSequential);
3622 | then OpenScope Block ${
3624 var_block_close(config2context(config), CloseSequential);
3627 ThenPartNL -> ThenPart OptNL ${
3631 // This scope is closed in CondSuffix
3632 WhileHead -> while OpenScope Block ${
3637 ForThen -> ForPart OptNL ThenPartNL ${
3645 // This scope is closed in CondSuffix
3646 WhilePart -> while OpenScope Expression Block ${
3647 $0.type = Xcond_statement;
3651 | WhileHead OptNL do Block ${
3652 $0.type = Xcond_statement;
3657 IfPart -> if OpenScope Expression OpenScope Block ${
3658 $0.type = Xcond_statement;
3661 var_block_close(config2context(config), CloseParallel);
3663 | if OpenScope Block OptNL then OpenScope Block ${
3664 $0.type = Xcond_statement;
3667 var_block_close(config2context(config), CloseParallel);
3671 // This scope is closed in CondSuffix
3672 SwitchPart -> switch OpenScope Expression ${
3675 | switch OpenScope Block ${
3679 ###### print exec cases
3681 case Xcond_statement:
3683 struct cond_statement *cs = cast(cond_statement, e);
3684 struct casepart *cp;
3686 do_indent(indent, "for");
3687 if (bracket) printf(" {\n"); else printf(":\n");
3688 print_exec(cs->forpart, indent+1, bracket);
3691 do_indent(indent, "} then {\n");
3693 do_indent(indent, "then:\n");
3694 print_exec(cs->thenpart, indent+1, bracket);
3696 if (bracket) do_indent(indent, "}\n");
3700 if (cs->condpart && cs->condpart->type == Xbinode &&
3701 cast(binode, cs->condpart)->op == Block) {
3703 do_indent(indent, "while {\n");
3705 do_indent(indent, "while:\n");
3706 print_exec(cs->condpart, indent+1, bracket);
3708 do_indent(indent, "} do {\n");
3710 do_indent(indent, "do:\n");
3711 print_exec(cs->dopart, indent+1, bracket);
3713 do_indent(indent, "}\n");
3715 do_indent(indent, "while ");
3716 print_exec(cs->condpart, 0, bracket);
3721 print_exec(cs->dopart, indent+1, bracket);
3723 do_indent(indent, "}\n");
3728 do_indent(indent, "switch");
3730 do_indent(indent, "if");
3731 if (cs->condpart && cs->condpart->type == Xbinode &&
3732 cast(binode, cs->condpart)->op == Block) {
3737 print_exec(cs->condpart, indent+1, bracket);
3739 do_indent(indent, "}\n");
3741 do_indent(indent, "then:\n");
3742 print_exec(cs->thenpart, indent+1, bracket);
3746 print_exec(cs->condpart, 0, bracket);
3752 print_exec(cs->thenpart, indent+1, bracket);
3754 do_indent(indent, "}\n");
3759 for (cp = cs->casepart; cp; cp = cp->next) {
3760 do_indent(indent, "case ");
3761 print_exec(cp->value, -1, 0);
3766 print_exec(cp->action, indent+1, bracket);
3768 do_indent(indent, "}\n");
3771 do_indent(indent, "else");
3776 print_exec(cs->elsepart, indent+1, bracket);
3778 do_indent(indent, "}\n");
3783 ###### propagate exec cases
3784 case Xcond_statement:
3786 // forpart and dopart must return Tnone
3787 // thenpart must return Tnone if there is a dopart,
3788 // otherwise it is like elsepart.
3790 // be bool if there is no casepart
3791 // match casepart->values if there is a switchpart
3792 // either be bool or match casepart->value if there
3794 // elsepart and casepart->action must match the return type
3795 // expected of this statement.
3796 struct cond_statement *cs = cast(cond_statement, prog);
3797 struct casepart *cp;
3799 t = propagate_types(cs->forpart, c, ok, Tnone, 0);
3800 if (!type_compat(Tnone, t, 0))
3802 t = propagate_types(cs->dopart, c, ok, Tnone, 0);
3803 if (!type_compat(Tnone, t, 0))
3806 t = propagate_types(cs->thenpart, c, ok, Tnone, 0);
3807 if (!type_compat(Tnone, t, 0))
3810 if (cs->casepart == NULL)
3811 propagate_types(cs->condpart, c, ok, Tbool, 0);
3813 /* Condpart must match case values, with bool permitted */
3815 for (cp = cs->casepart;
3816 cp && !t; cp = cp->next)
3817 t = propagate_types(cp->value, c, ok, NULL, 0);
3818 if (!t && cs->condpart)
3819 t = propagate_types(cs->condpart, c, ok, NULL, Rboolok);
3820 // Now we have a type (I hope) push it down
3822 for (cp = cs->casepart; cp; cp = cp->next)
3823 propagate_types(cp->value, c, ok, t, 0);
3824 propagate_types(cs->condpart, c, ok, t, Rboolok);
3827 // (if)then, else, and case parts must return expected type.
3828 if (!cs->dopart && !type)
3829 type = propagate_types(cs->thenpart, c, ok, NULL, rules);
3831 type = propagate_types(cs->elsepart, c, ok, NULL, rules);
3832 for (cp = cs->casepart;
3835 type = propagate_types(cp->action, c, ok, NULL, rules);
3838 propagate_types(cs->thenpart, c, ok, type, rules);
3839 propagate_types(cs->elsepart, c, ok, type, rules);
3840 for (cp = cs->casepart; cp ; cp = cp->next)
3841 propagate_types(cp->action, c, ok, type, rules);
3847 ###### interp exec cases
3848 case Xcond_statement:
3850 struct value v, cnd;
3851 struct casepart *cp;
3852 struct cond_statement *c = cast(cond_statement, e);
3855 interp_exec(c->forpart);
3858 cnd = interp_exec(c->condpart);
3861 if (!(cnd.type == Tnone ||
3862 (cnd.type == Tbool && cnd.bool != 0)))
3864 // cnd is Tnone or Tbool, doesn't need to be freed
3866 interp_exec(c->dopart);
3869 rv = interp_exec(c->thenpart);
3870 if (rv.type != Tnone || !c->dopart)
3874 } while (c->dopart);
3876 for (cp = c->casepart; cp; cp = cp->next) {
3877 v = interp_exec(cp->value);
3878 if (value_cmp(v, cnd) == 0) {
3881 rv = interp_exec(cp->action);
3888 rv = interp_exec(c->elsepart);
3895 ### Top level structure
3897 All the language elements so far can be used in various places. Now
3898 it is time to clarify what those places are.
3900 At the top level of a file there will be a number of declarations.
3901 Many of the things that can be declared haven't been described yet,
3902 such as functions, procedures, imports, and probably more.
3903 For now there are two sorts of things that can appear at the top
3904 level. They are predefined constants, `struct` types, and the main
3905 program. While the syntax will allow the main program to appear
3906 multiple times, that will trigger an error if it is actually attempted.
3908 The various declarations do not return anything. They store the
3909 various declarations in the parse context.
3911 ###### Parser: grammar
3914 Ocean -> DeclarationList
3916 DeclarationList -> Declaration
3917 | DeclarationList Declaration
3919 Declaration -> DeclareConstant
3924 ## top level grammar
3926 ### The `const` section
3928 As well as being defined in with the code that uses them, constants
3929 can be declared at the top level. These have full-file scope, so they
3930 are always `InScope`. The value of a top level constant can be given
3931 as an expression, and this is evaluated immediately rather than in the
3932 later interpretation stage. Once we add functions to the language, we
3933 will need rules concern which, if any, can be used to define a top
3936 Constants are defined in a section that starts with the reserved word
3937 `const` and then has a block with a list of assignment statements.
3938 For syntactic consistency, these must use the double-colon syntax to
3939 make it clear that they are constants. Type can also be given: if
3940 not, the type will be determined during analysis, as with other
3943 As the types constants are inserted at the head of a list, printing
3944 them in the same order that they were read is not straight forward.
3945 We take a quadratic approach here and count the number of constants
3946 (variables of depth 0), then count down from there, each time
3947 searching through for the Nth constant for decreasing N.
3949 ###### top level grammar
3951 DeclareConstant -> const Open ConstList Close
3952 | const Open Newlines ConstList Close
3953 | const Open SimpleConstList }
3954 | const Open Newlines SimpleConstList }
3956 | const SimpleConstList
3958 ConstList -> ComplexConsts
3959 ComplexConsts -> ComplexConst ComplexConsts
3961 ComplexConst -> SimpleConstList NEWLINE
3962 SimpleConstList -> Const ; SimpleConstList
3964 | Const ; SimpleConstList ;
3967 CType -> Type ${ $0 = $<1; }$
3970 Const -> IDENTIFIER :: CType = Expression ${ {
3974 v = var_decl(config2context(config), $1.txt);
3976 struct var *var = new_pos(var, $1);
3977 v->where_decl = var;
3982 v = var_ref(config2context(config), $1.txt);
3983 tok_err(config2context(config), "error: name already declared", &$1);
3984 type_err(config2context(config), "info: this is where '%v' was first declared",
3985 v->where_decl, NULL, 0, NULL);
3989 propagate_types($5, config2context(config), &ok, $3, 0);
3992 config2context(config)->parse_error = 1;
3994 v->val = interp_exec($5);
3998 ###### print const decls
4003 while (target != 0) {
4005 for (v = context.in_scope; v; v=v->in_scope)
4006 if (v->depth == 0) {
4017 printf(" %.*s :: ", v->name->name.len, v->name->name.txt);
4018 type_print(v->val.type, stdout);
4020 if (v->val.type == Tstr)
4022 print_value(v->val);
4023 if (v->val.type == Tstr)
4031 ### Finally the whole program.
4033 Somewhat reminiscent of Pascal a (current) Ocean program starts with
4034 the keyword "program" and a list of variable names which are assigned
4035 values from command line arguments. Following this is a `block` which
4036 is the code to execute. Unlike Pascal, constants and other
4037 declarations come *before* the program.
4039 As this is the top level, several things are handled a bit
4041 The whole program is not interpreted by `interp_exec` as that isn't
4042 passed the argument list which the program requires. Similarly type
4043 analysis is a bit more interesting at this level.
4048 ###### top level grammar
4050 DeclareProgram -> Program ${ {
4051 struct parse_context *c = config2context(config);
4053 type_err(c, "Program defined a second time",
4061 Program -> program OpenScope Varlist Block OptNL ${
4064 $0->left = reorder_bilist($<3);
4066 var_block_close(config2context(config), CloseSequential);
4067 if (config2context(config)->scope_stack) abort();
4070 tok_err(config2context(config),
4071 "error: unhandled parse error", &$1);
4074 Varlist -> Varlist ArgDecl ${
4083 ArgDecl -> IDENTIFIER ${ {
4084 struct variable *v = var_decl(config2context(config), $1.txt);
4091 ###### print binode cases
4093 do_indent(indent, "program");
4094 for (b2 = cast(binode, b->left); b2; b2 = cast(binode, b2->right)) {
4096 print_exec(b2->left, 0, 0);
4102 print_exec(b->right, indent+1, bracket);
4104 do_indent(indent, "}\n");
4107 ###### propagate binode cases
4108 case Program: abort(); // NOTEST
4110 ###### core functions
4112 static int analyse_prog(struct exec *prog, struct parse_context *c)
4114 struct binode *b = cast(binode, prog);
4121 propagate_types(b->right, c, &ok, Tnone, 0);
4126 for (b = cast(binode, b->left); b; b = cast(binode, b->right)) {
4127 struct var *v = cast(var, b->left);
4128 if (!v->var->val.type) {
4129 v->var->where_set = b;
4130 v->var->val = val_prepare(Tstr);
4133 b = cast(binode, prog);
4136 propagate_types(b->right, c, &ok, Tnone, 0);
4141 /* Make sure everything is still consistent */
4142 propagate_types(b->right, c, &ok, Tnone, 0);
4146 static void interp_prog(struct exec *prog, char **argv)
4148 struct binode *p = cast(binode, prog);
4154 al = cast(binode, p->left);
4156 struct var *v = cast(var, al->left);
4157 struct value *vl = &v->var->val;
4159 if (argv[0] == NULL) {
4160 printf("Not enough args\n");
4163 al = cast(binode, al->right);
4165 *vl = parse_value(vl->type, argv[0]);
4166 if (vl->type == NULL)
4170 v = interp_exec(p->right);
4174 ###### interp binode cases
4175 case Program: abort(); // NOTEST
4177 ## And now to test it out.
4179 Having a language requires having a "hello world" program. I'll
4180 provide a little more than that: a program that prints "Hello world"
4181 finds the GCD of two numbers, prints the first few elements of
4182 Fibonacci, performs a binary search for a number, and a few other
4183 things which will likely grow as the languages grows.
4185 ###### File: oceani.mk
4188 @echo "===== TEST ====="
4189 ./oceani --section "test: hello" oceani.mdc 55 33
4195 four ::= 2 + 2 ; five ::= 10/2
4196 const pie ::= "I like Pie";
4197 cake ::= "The cake is"
4206 print "Hello World, what lovely oceans you have!"
4207 print "Are there", five, "?"
4208 print pi, pie, "but", cake
4210 /* When a variable is defined in both branches of an 'if',
4211 * and used afterwards, the variables are merged.
4217 print "Is", A, "bigger than", B,"? ", bigger
4218 /* If a variable is not used after the 'if', no
4219 * merge happens, so types can be different
4222 double:string = "yes"
4223 print A, "is more than twice", B, "?", double
4226 print "double", B, "is", double
4231 if a > 0 and then b > 0:
4237 print "GCD of", A, "and", B,"is", a
4239 print a, "is not positive, cannot calculate GCD"
4241 print b, "is not positive, cannot calculate GCD"
4246 print "Fibonacci:", f1,f2,
4247 then togo = togo - 1
4255 /* Binary search... */
4260 mid := (lo + hi) / 2
4272 print "Yay, I found", target
4274 print "Closest I found was", mid
4279 // "middle square" PRNG. Not particularly good, but one my
4280 // Dad taught me - the first one I ever heard of.
4281 for i:=1; then i = i + 1; while i < size:
4282 n := list[i-1] * list[i-1]
4283 list[i] = (n / 100) % 10000
4285 print "Before sort:",
4286 for i:=0; then i = i + 1; while i < size:
4290 for i := 1; then i=i+1; while i < size:
4291 for j:=i-1; then j=j-1; while j >= 0:
4292 if list[j] > list[j+1]:
4296 print " After sort:",
4297 for i:=0; then i = i + 1; while i < size:
4303 bob.alive = (bob.name == "Hello")
4304 print "bob", "is" if bob.alive else "isn't", "alive"