1 # Ocean Interpreter - Stoney 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 second version of the interpreter exists to test out the
33 structured statement providing conditions and iteration, and simple
34 variable scoping. Clearly we need some minimal other functionality so
35 that values can be tested and instructions iterated over. All that
36 functionality is clearly not normative at this stage (not that
37 anything is **really** normative yet) and will change, so early test
38 code will certainly break in later versions.
40 The under-test parts of the language are:
42 - conditional/looping structured statements
43 - the `use` statement which is needed for that
44 - Variable binding using ":=" and "::=", and assignment using "=".
46 Elements which are present to make a usable language are:
48 - "blocks" of multiple statements.
49 - `pass`: a statement which does nothing.
50 - expressions: `+`, `-`, `*`, `/`, `%` can apply to numbers and `++` can
51 catenate strings. `and`, `or`, `not` manipulate Booleans, and
52 normal comparison operators can work on all three types.
53 - `print`: will print the values in a list of expressions.
54 - `program`: is given a list of identifiers to initialize from
59 Versions of the interpreter which obviously do not support a complete
60 language will be named after creeks and streams. This one is Stoney
63 Once we have something reasonably resembling a complete language, the
64 names of rivers will be used.
65 Early versions of the compiler will be named after seas. Major
66 releases of the compiler will be named after oceans. Hopefully I will
67 be finished once I get to the Pacific Ocean release.
71 As well as parsing and executing a program, the interpreter can print
72 out the program from the parsed internal structure. This is useful
73 for validating the parsing.
74 So the main requirements of the interpreter are:
76 - Parse the program, possibly with tracing,
77 - Analyse the parsed program to ensure consistency,
79 - Execute the program.
81 This is all performed by a single C program extracted with
84 There will be two formats for printing the program: a default and one
85 that uses bracketing. So a `--bracket` command line option is needed
86 for that. Normally the first code section found is used, however an
87 alternate section can be requested so that a file (such as this one)
88 can contain multiple programs This is effected with the `--section`
91 This code must be compiled with `-fplan9-extensions` so that anonymous
92 structures can be used.
94 ###### File: oceani.mk
96 myCFLAGS := -Wall -g -fplan9-extensions
97 CFLAGS := $(filter-out $(myCFLAGS),$(CFLAGS)) $(myCFLAGS)
98 myLDLIBS:= libparser.o libscanner.o libmdcode.o -licuuc
99 LDLIBS := $(filter-out $(myLDLIBS),$(LDLIBS)) $(myLDLIBS)
101 all :: $(LDLIBS) oceani
102 oceani.c oceani.h : oceani.mdc parsergen
103 ./parsergen -o oceani --LALR --tag Parser oceani.mdc
104 oceani.mk: oceani.mdc md2c
107 oceani: oceani.o $(LDLIBS)
108 $(CC) $(CFLAGS) -o oceani oceani.o $(LDLIBS)
110 ###### Parser: header
113 struct parse_context {
114 struct token_config config;
123 #define container_of(ptr, type, member) ({ \
124 const typeof( ((type *)0)->member ) *__mptr = (ptr); \
125 (type *)( (char *)__mptr - offsetof(type,member) );})
127 #define config2context(_conf) container_of(_conf, struct parse_context, \
136 #include <sys/mman.h>
155 static char Usage[] = "Usage: oceani --trace --print --noexec --brackets"
156 "--section=SectionName prog.ocn\n";
157 static const struct option long_options[] = {
158 {"trace", 0, NULL, 't'},
159 {"print", 0, NULL, 'p'},
160 {"noexec", 0, NULL, 'n'},
161 {"brackets", 0, NULL, 'b'},
162 {"section", 1, NULL, 's'},
165 const char *options = "tpnbs";
166 int main(int argc, char *argv[])
172 char *section = NULL;
173 struct parse_context context = {
175 .ignored = (1 << TK_line_comment)
176 | (1 << TK_block_comment),
177 .number_chars = ".,_+-",
182 int doprint=0, dotrace=0, doexec=1, brackets=0;
184 while ((opt = getopt_long(argc, argv, options, long_options, NULL))
187 case 't': dotrace=1; break;
188 case 'p': doprint=1; break;
189 case 'n': doexec=0; break;
190 case 'b': brackets=1; break;
191 case 's': section = optarg; break;
192 default: fprintf(stderr, Usage);
196 if (optind >= argc) {
197 fprintf(stderr, "oceani: no input file given\n");
200 fd = open(argv[optind], O_RDONLY);
202 fprintf(stderr, "oceani: cannot open %s\n", argv[optind]);
205 context.file_name = argv[optind];
206 len = lseek(fd, 0, 2);
207 file = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
208 s = code_extract(file, file+len, NULL);
210 fprintf(stderr, "oceani: could not find any code in %s\n",
215 ## context initialization
219 for (ss = s; ss; ss = ss->next) {
220 struct text sec = ss->section;
221 if (sec.len == strlen(section) &&
222 strncmp(sec.txt, section, sec.len) == 0)
226 parse_oceani(ss->code, &context.config,
227 dotrace ? stderr : NULL);
229 fprintf(stderr, "oceani: cannot find section %s\n",
234 parse_oceani(s->code, &context.config,
235 dotrace ? stderr : NULL);
237 fprintf(stderr, "oceani: no program found.\n");
238 context.parse_error = 1;
240 if (context.prog && doprint)
241 print_exec(context.prog, 0, brackets);
242 if (context.prog && doexec && !context.parse_error) {
243 if (!analyse_prog(context.prog, &context)) {
244 fprintf(stderr, "oceani: type error in program - not running.\n");
247 interp_prog(context.prog, argv+optind+1);
250 free_exec(context.prog);
253 struct section *t = s->next;
259 ## free context types
260 exit(context.parse_error ? 1 : 0);
265 The four requirements of parse, analyse, print, interpret apply to
266 each language element individually so that is how most of the code
269 Three of the four are fairly self explanatory. The one that requires
270 a little explanation is the analysis step.
272 The current language design does not require the types of variables to
273 be declared, but they must still have a single type. Different
274 operations impose different requirements on the variables, for example
275 addition requires both arguments to be numeric, and assignment
276 requires the variable on the left to have the same type as the
277 expression on the right.
279 Analysis involves propagating these type requirements around and
280 consequently setting the type of each variable. If any requirements
281 are violated (e.g. a string is compared with a number) or if a
282 variable needs to have two different types, then an error is raised
283 and the program will not run.
285 If the same variable is declared in both branchs of an 'if/else', or
286 in all cases of a 'switch' then the multiple instances may be merged
287 into just one variable if the variable is references after the
288 conditional statement. When this happens, the types must naturally be
289 consistent across all the branches. When the variable is not used
290 outside the if, the variables in the different branches are distinct
291 and can be of different types.
293 Determining the types of all variables early is important for
294 processing command line arguments. These can be assigned to any type
295 of variable, but we must first know the correct type so any required
296 conversion can happen. If a variable is associated with a command
297 line argument but no type can be interpreted (e.g. the variable is
298 only ever used in a `print` statement), then the type is set to
301 Undeclared names may only appear in "use" statements and "case" expressions.
302 These names are given a type of "label" and a unique value.
303 This allows them to fill the role of a name in an enumerated type, which
304 is useful for testing the `switch` statement.
306 As we will see, the condition part of a `while` statement can return
307 either a Boolean or some other type. This requires that the expect
308 type that gets passed around comprises a type (`enum vtype`) and a
309 flag to indicate that `Vbool` is also permitted.
311 As there are, as yet, no distinct types that are compatible, there
312 isn't much subtlety in the analysis. When we have distinct number
313 types, this will become more interesting.
317 When analysis discovers an inconsistency it needs to report an error;
318 just refusing to run the code ensures that the error doesn't cascade,
319 but by itself it isn't very useful. A clear understand of the sort of
320 error message that are useful will help guide the process of analysis.
322 At a simplistic level, the only sort of error that type analysis can
323 report is that the type of some construct doesn't match a contextual
324 requirement. For example, in `4 + "hello"` the addition provides a
325 contextual requirement for numbers, but `"hello"` is not a number. In
326 this particular example no further information is needed as the types
327 are obvious from local information. When a variable is involved that
328 isn't the case. It may be helpful to explain why the variable has a
329 particular type, by indicating the location where the type was set,
330 whether by declaration or usage.
332 Using a recursive-descent analysis we can easily detect a problem at
333 multiple locations. In "`hello:= "there"; 4 + hello`" the addition
334 will detect that one argument is not a number and the usage of `hello`
335 will detect that a number was wanted, but not provided. In this
336 (early) version of the language, we will generate error reports at
337 multiple locations, so the use of `hello` will report an error and
338 explain were the value was set, and the addition will report an error
339 and say why numbers are needed. To be able to report locations for
340 errors, each language element will need to record a file location
341 (line and column) and each variable will need to record the language
342 element where its type was set. For now we will assume that each line
343 of an error message indicates one location in the file, and up to 2
344 types. So we provide a `printf`-like function which takes a format, a
345 language (a `struct exec` which has not yet been introduced), and 2
346 types. "`%1`" reports the first type, "`%2`" reports the second. We
347 will need a function to print the location, once we know how that is
348 stored. As will be explained later, there are sometimes extra rules for
349 type matching and they might affect error messages, we need to pass those
352 As well as type errors, we sometimes need to report problems with
353 tokens, which might be unexpected or might name a type that has not
354 been defined. For these we have `tok_err()` which reports an error
355 with a given token. Each of the error functions sets the flag in the
356 context so indicate that parsing failed.
360 static void fput_loc(struct exec *loc, FILE *f);
362 ###### core functions
364 static void type_err(struct parse_context *c,
365 char *fmt, struct exec *loc,
366 struct type *t1, int rules, struct type *t2)
368 fprintf(stderr, "%s:", c->file_name);
369 fput_loc(loc, stderr);
370 for (; *fmt ; fmt++) {
377 case '%': fputc(*fmt, stderr); break; // NOTEST
378 default: fputc('?', stderr); break; // NOTEST
380 type_print(t1, stderr);
383 type_print(t2, stderr);
392 static void tok_err(struct parse_context *c, char *fmt, struct token *t)
394 fprintf(stderr, "%s:%d:%d: %s: %.*s\n", c->file_name, t->line, t->col, fmt,
395 t->txt.len, t->txt.txt);
401 One last introductory step before detailing the language elements and
402 providing their four requirements is to establish the data structures
403 to store these elements.
405 There are two key objects that we need to work with: executable
406 elements which comprise the program, and values which the program
407 works with. Between these are the variables in their various scopes
408 which hold the values, and types which classify the values stored and
409 manipulatd by executables.
413 Values come in a wide range of types, with more likely to be added.
414 Each type needs to be able to parse and print its own values (for
415 convenience at least) as well as to compare two values, at least for
416 equality and possibly for order. For now, values might need to be
417 duplicated and freed, though eventually such manipulations will be
418 better integrated into the language.
420 Rather than requiring every numeric type to support all numeric
421 operations (add, multiple, etc), we allow types to be able to present
422 as one of a few standard types: integer, float, and fraction. The
423 existance of these conversion functions enable types to determine if
424 they are compatible with other types.
426 Named type are stored in a simple linked list. Objects of each type are "values"
427 which are often passed around by value.
434 ## value union fields
441 struct value (*init)(struct type *type);
442 struct value (*prepare)(struct type *type);
443 struct value (*parse)(struct type *type, char *str);
444 void (*print)(struct value val);
445 void (*print_type)(struct type *type, FILE *f);
446 int (*cmp_order)(struct value v1, struct value v2);
447 int (*cmp_eq)(struct value v1, struct value v2);
448 struct value (*dup)(struct value val);
449 void (*free)(struct value val);
450 int (*compat)(struct type *this, struct type *other);
451 long long (*to_int)(struct value *v);
452 double (*to_float)(struct value *v);
453 int (*to_mpq)(mpq_t *q, struct value *v);
461 struct type *typelist;
465 static struct type *find_type(struct parse_context *c, struct text s)
467 struct type *l = c->typelist;
470 text_cmp(l->name, s) != 0)
475 static struct type *add_type(struct parse_context *c, struct text s,
480 n = calloc(1, sizeof(*n));
483 n->next = c->typelist;
488 static void free_type(struct type *t)
490 /* The type is always a reference to something in the
491 * context, so we don't need to free anything.
495 static void free_value(struct value v)
501 static int type_compat(struct type *require, struct type *have, int rules)
503 if ((rules & Rboolok) && have == Tbool)
505 if ((rules & Rnolabel) && have == Tlabel)
507 if (!require || !have)
511 return require->compat(require, have);
513 return require == have;
516 static void type_print(struct type *type, FILE *f)
519 fputs("*unknown*type*", f);
520 else if (type->name.len)
521 fprintf(f, "%.*s", type->name.len, type->name.txt);
522 else if (type->print_type)
523 type->print_type(type, f);
525 fputs("*invalid*type*", f); // NOTEST
528 static struct value val_prepare(struct type *type)
533 return type->prepare(type);
538 static struct value val_init(struct type *type)
543 return type->init(type);
548 static struct value dup_value(struct value v)
551 return v.type->dup(v);
555 static int value_cmp(struct value left, struct value right)
557 if (left.type && left.type->cmp_order)
558 return left.type->cmp_order(left, right);
559 if (left.type && left.type->cmp_eq)
560 return left.type->cmp_eq(left, right);
564 static void print_value(struct value v)
566 if (v.type && v.type->print)
569 printf("*Unknown*"); // NOTEST
572 static struct value parse_value(struct type *type, char *arg)
576 if (type && type->parse)
577 return type->parse(type, arg);
578 rv.type = NULL; // NOTEST
584 static void free_value(struct value v);
585 static int type_compat(struct type *require, struct type *have, int rules);
586 static void type_print(struct type *type, FILE *f);
587 static struct value val_init(struct type *type);
588 static struct value dup_value(struct value v);
589 static int value_cmp(struct value left, struct value right);
590 static void print_value(struct value v);
591 static struct value parse_value(struct type *type, char *arg);
593 ###### free context types
595 while (context.typelist) {
596 struct type *t = context.typelist;
598 context.typelist = t->next;
604 Values of the base types can be numbers, which we represent as
605 multi-precision fractions, strings, Booleans and labels. When
606 analysing the program we also need to allow for places where no value
607 is meaningful (type `Tnone`) and where we don't know what type to
608 expect yet (type is `NULL`).
610 Values are never shared, they are always copied when used, and freed
611 when no longer needed.
613 When propagating type information around the program, we need to
614 determine if two types are compatible, where type `NULL` is compatible
615 with anything. There are two special cases with type compatibility,
616 both related to the Conditional Statement which will be described
617 later. In some cases a Boolean can be accepted as well as some other
618 primary type, and in others any type is acceptable except a label (`Vlabel`).
619 A separate function encode these cases will simplify some code later.
621 When assigning command line arguments to variables, we need to be able
622 to parse each type from a string.
630 myLDLIBS := libnumber.o libstring.o -lgmp
631 LDLIBS := $(filter-out $(myLDLIBS),$(LDLIBS)) $(myLDLIBS)
633 ###### type union fields
634 enum vtype {Vnone, Vstr, Vnum, Vbool, Vlabel} vtype;
636 ###### value union fields
643 static void _free_value(struct value v)
645 switch (v.type->vtype) {
647 case Vstr: free(v.str.txt); break;
648 case Vnum: mpq_clear(v.num); break;
654 ###### value functions
656 static struct value _val_prepare(struct type *type)
661 switch(type->vtype) {
665 memset(&rv.num, 0, sizeof(rv.num));
681 static struct value _val_init(struct type *type)
686 switch(type->vtype) {
687 case Vnone: // NOTEST
690 mpq_init(rv.num); break;
692 rv.str.txt = malloc(1);
698 case Vlabel: // NOTEST
699 rv.label = NULL; // NOTEST
705 static struct value _dup_value(struct value v)
709 switch (rv.type->vtype) {
710 case Vnone: // NOTEST
720 mpq_set(rv.num, v.num);
723 rv.str.len = v.str.len;
724 rv.str.txt = malloc(rv.str.len);
725 memcpy(rv.str.txt, v.str.txt, v.str.len);
731 static int _value_cmp(struct value left, struct value right)
734 if (left.type != right.type)
735 return left.type - right.type; // NOTEST
736 switch (left.type->vtype) {
737 case Vlabel: cmp = left.label == right.label ? 0 : 1; break;
738 case Vnum: cmp = mpq_cmp(left.num, right.num); break;
739 case Vstr: cmp = text_cmp(left.str, right.str); break;
740 case Vbool: cmp = left.bool - right.bool; break;
741 case Vnone: cmp = 0; // NOTEST
746 static void _print_value(struct value v)
748 switch (v.type->vtype) {
749 case Vnone: // NOTEST
750 printf("*no-value*"); break; // NOTEST
751 case Vlabel: // NOTEST
752 printf("*label-%p*", v.label); break; // NOTEST
754 printf("%.*s", v.str.len, v.str.txt); break;
756 printf("%s", v.bool ? "True":"False"); break;
761 mpf_set_q(fl, v.num);
762 gmp_printf("%Fg", fl);
769 static struct value _parse_value(struct type *type, char *arg)
777 switch(type->vtype) {
778 case Vlabel: // NOTEST
779 case Vnone: // NOTEST
780 val.type = NULL; // NOTEST
783 val.str.len = strlen(arg);
784 val.str.txt = malloc(val.str.len);
785 memcpy(val.str.txt, arg, val.str.len);
792 tx.txt = arg; tx.len = strlen(tx.txt);
793 if (number_parse(val.num, tail, tx) == 0)
796 mpq_neg(val.num, val.num);
798 printf("Unsupported suffix: %s\n", arg);
803 if (strcasecmp(arg, "true") == 0 ||
804 strcmp(arg, "1") == 0)
806 else if (strcasecmp(arg, "false") == 0 ||
807 strcmp(arg, "0") == 0)
810 printf("Bad bool: %s\n", arg);
818 static void _free_value(struct value v);
820 static struct type base_prototype = {
822 .prepare = _val_prepare,
823 .parse = _parse_value,
824 .print = _print_value,
825 .cmp_order = _value_cmp,
826 .cmp_eq = _value_cmp,
831 static struct type *Tbool, *Tstr, *Tnum, *Tnone, *Tlabel;
834 static struct type *add_base_type(struct parse_context *c, char *n, enum vtype vt)
836 struct text txt = { n, strlen(n) };
839 t = add_type(c, txt, &base_prototype);
844 ###### context initialization
846 Tbool = add_base_type(&context, "Boolean", Vbool);
847 Tstr = add_base_type(&context, "string", Vstr);
848 Tnum = add_base_type(&context, "number", Vnum);
849 Tnone = add_base_type(&context, "none", Vnone);
850 Tlabel = add_base_type(&context, "label", Vlabel);
854 Variables are scoped named values. We store the names in a linked
855 list of "bindings" sorted lexically, and use sequential search and
862 struct binding *next; // in lexical order
866 This linked list is stored in the parse context so that "reduce"
867 functions can find or add variables, and so the analysis phase can
868 ensure that every variable gets a type.
872 struct binding *varlist; // In lexical order
876 static struct binding *find_binding(struct parse_context *c, struct text s)
878 struct binding **l = &c->varlist;
883 (cmp = text_cmp((*l)->name, s)) < 0)
887 n = calloc(1, sizeof(*n));
894 Each name can be linked to multiple variables defined in different
895 scopes. Each scope starts where the name is declared and continues
896 until the end of the containing code block. Scopes of a given name
897 cannot nest, so a declaration while a name is in-scope is an error.
899 ###### binding fields
900 struct variable *var;
904 struct variable *previous;
906 struct binding *name;
907 struct exec *where_decl;// where name was declared
908 struct exec *where_set; // where type was set
912 While the naming seems strange, we include local constants in the
913 definition of variables. A name declared `var := value` can
914 subsequently be changed, but a name declared `var ::= value` cannot -
917 ###### variable fields
920 Scopes in parallel branches can be partially merged. More
921 specifically, if a given name is declared in both branches of an
922 if/else then its scope is a candidate for merging. Similarly if
923 every branch of an exhaustive switch (e.g. has an "else" clause)
924 declares a given name, then the scopes from the branches are
925 candidates for merging.
927 Note that names declared inside a loop (which is only parallel to
928 itself) are never visible after the loop. Similarly names defined in
929 scopes which are not parallel, such as those started by `for` and
930 `switch`, are never visible after the scope. Only variables defined in
931 both `then` and `else` (including the implicit then after an `if`, and
932 excluding `then` used with `for`) and in all `case`s and `else` of a
933 `switch` or `while` can be visible beyond the `if`/`switch`/`while`.
935 Labels, which are a bit like variables, follow different rules.
936 Labels are not explicitly declared, but if an undeclared name appears
937 in a context where a label is legal, that effectively declares the
938 name as a label. The declaration remains in force (or in scope) at
939 least to the end of the immediately containing block and conditionally
940 in any larger containing block which does not declare the name in some
941 other way. Importantly, the conditional scope extension happens even
942 if the label is only used in one parallel branch of a conditional --
943 when used in one branch it is treated as having been declared in all
946 Merge candidates are tentatively visible beyond the end of the
947 branching statement which creates them. If the name is used, the
948 merge is affirmed and they become a single variable visible at the
949 outer layer. If not - if it is redeclared first - the merge lapses.
951 To track scopes we have an extra stack, implemented as a linked list,
952 which roughly parallels the parse stack and which is used exclusively
953 for scoping. When a new scope is opened, a new frame is pushed and
954 the child-count of the parent frame is incremented. This child-count
955 is used to distinguish between the first of a set of parallel scopes,
956 in which declared variables must not be in scope, and subsequent
957 branches, whether they must already be conditionally scoped.
959 To push a new frame *before* any code in the frame is parsed, we need a
960 grammar reduction. This is most easily achieved with a grammar
961 element which derives the empty string, and creates the new scope when
962 it is recognized. This can be placed, for example, between a keyword
963 like "if" and the code following it.
967 struct scope *parent;
973 struct scope *scope_stack;
976 static void scope_pop(struct parse_context *c)
978 struct scope *s = c->scope_stack;
980 c->scope_stack = s->parent;
985 static void scope_push(struct parse_context *c)
987 struct scope *s = calloc(1, sizeof(*s));
989 c->scope_stack->child_count += 1;
990 s->parent = c->scope_stack;
998 OpenScope -> ${ scope_push(config2context(config)); }$
1001 Each variable records a scope depth and is in one of four states:
1003 - "in scope". This is the case between the declaration of the
1004 variable and the end of the containing block, and also between
1005 the usage with affirms a merge and the end of that block.
1007 The scope depth is not greater than the current parse context scope
1008 nest depth. When the block of that depth closes, the state will
1009 change. To achieve this, all "in scope" variables are linked
1010 together as a stack in nesting order.
1012 - "pending". The "in scope" block has closed, but other parallel
1013 scopes are still being processed. So far, every parallel block at
1014 the same level that has closed has declared the name.
1016 The scope depth is the depth of the last parallel block that
1017 enclosed the declaration, and that has closed.
1019 - "conditionally in scope". The "in scope" block and all parallel
1020 scopes have closed, and no further mention of the name has been
1021 seen. This state includes a secondary nest depth which records the
1022 outermost scope seen since the variable became conditionally in
1023 scope. If a use of the name is found, the variable becomes "in
1024 scope" and that secondary depth becomes the recorded scope depth.
1025 If the name is declared as a new variable, the old variable becomes
1026 "out of scope" and the recorded scope depth stays unchanged.
1028 - "out of scope". The variable is neither in scope nor conditionally
1029 in scope. It is permanently out of scope now and can be removed from
1030 the "in scope" stack.
1033 ###### variable fields
1034 int depth, min_depth;
1035 enum { OutScope, PendingScope, CondScope, InScope } scope;
1036 struct variable *in_scope;
1038 ###### parse context
1040 struct variable *in_scope;
1042 All variables with the same name are linked together using the
1043 'previous' link. Those variable that have
1044 been affirmatively merged all have a 'merged' pointer that points to
1045 one primary variable - the most recently declared instance. When
1046 merging variables, we need to also adjust the 'merged' pointer on any
1047 other variables that had previously been merged with the one that will
1048 no longer be primary.
1050 ###### variable fields
1051 struct variable *merged;
1053 ###### ast functions
1055 static void variable_merge(struct variable *primary, struct variable *secondary)
1059 if (primary->merged)
1061 primary = primary->merged;
1063 for (v = primary->previous; v; v=v->previous)
1064 if (v == secondary || v == secondary->merged ||
1065 v->merged == secondary ||
1066 (v->merged && v->merged == secondary->merged)) {
1067 v->scope = OutScope;
1068 v->merged = primary;
1072 ###### free context vars
1074 while (context.varlist) {
1075 struct binding *b = context.varlist;
1076 struct variable *v = b->var;
1077 context.varlist = b->next;
1080 struct variable *t = v;
1088 #### Manipulating Bindings
1090 When a name is conditionally visible, a new declaration discards the
1091 old binding - the condition lapses. Conversely a usage of the name
1092 affirms the visibility and extends it to the end of the containing
1093 block - i.e. the block that contains both the original declaration and
1094 the latest usage. This is determined from `min_depth`. When a
1095 conditionally visible variable gets affirmed like this, it is also
1096 merged with other conditionally visible variables with the same name.
1098 When we parse a variable declaration we either signal an error if the
1099 name is currently bound, or create a new variable at the current nest
1100 depth if the name is unbound or bound to a conditionally scoped or
1101 pending-scope variable. If the previous variable was conditionally
1102 scoped, it and its homonyms becomes out-of-scope.
1104 When we parse a variable reference (including non-declarative
1105 assignment) we signal an error if the name is not bound or is bound to
1106 a pending-scope variable; update the scope if the name is bound to a
1107 conditionally scoped variable; or just proceed normally if the named
1108 variable is in scope.
1110 When we exit a scope, any variables bound at this level are either
1111 marked out of scope or pending-scoped, depending on whether the
1112 scope was sequential or parallel.
1114 When exiting a parallel scope we check if there are any variables that
1115 were previously pending and are still visible. If there are, then
1116 there weren't redeclared in the most recent scope, so they cannot be
1117 merged and must become out-of-scope. If it is not the first of
1118 parallel scopes (based on `child_count`), we check that there was a
1119 previous binding that is still pending-scope. If there isn't, the new
1120 variable must now be out-of-scope.
1122 When exiting a sequential scope that immediately enclosed parallel
1123 scopes, we need to resolve any pending-scope variables. If there was
1124 no `else` clause, and we cannot determine that the `switch` was exhaustive,
1125 we need to mark all pending-scope variable as out-of-scope. Otherwise
1126 all pending-scope variables become conditionally scoped.
1129 enum closetype { CloseSequential, CloseParallel, CloseElse };
1131 ###### ast functions
1133 static struct variable *var_decl(struct parse_context *c, struct text s)
1135 struct binding *b = find_binding(c, s);
1136 struct variable *v = b->var;
1138 switch (v ? v->scope : OutScope) {
1140 /* Caller will report the error */
1144 v && v->scope == CondScope;
1146 v->scope = OutScope;
1150 v = calloc(1, sizeof(*v));
1151 v->previous = b->var;
1154 v->min_depth = v->depth = c->scope_depth;
1156 v->in_scope = c->in_scope;
1158 v->val = val_prepare(NULL);
1162 static struct variable *var_ref(struct parse_context *c, struct text s)
1164 struct binding *b = find_binding(c, s);
1165 struct variable *v = b->var;
1166 struct variable *v2;
1168 switch (v ? v->scope : OutScope) {
1171 /* Signal an error - once that is possible */
1174 /* All CondScope variables of this name need to be merged
1175 * and become InScope
1177 v->depth = v->min_depth;
1179 for (v2 = v->previous;
1180 v2 && v2->scope == CondScope;
1182 variable_merge(v, v2);
1190 static void var_block_close(struct parse_context *c, enum closetype ct)
1192 /* close of all variables that are in_scope */
1193 struct variable *v, **vp, *v2;
1196 for (vp = &c->in_scope;
1197 v = *vp, v && v->depth > c->scope_depth && v->min_depth > c->scope_depth;
1201 case CloseParallel: /* handle PendingScope */
1205 if (c->scope_stack->child_count == 1)
1206 v->scope = PendingScope;
1207 else if (v->previous &&
1208 v->previous->scope == PendingScope)
1209 v->scope = PendingScope;
1210 else if (v->val.type == Tlabel)
1211 v->scope = PendingScope;
1212 else if (v->name->var == v)
1213 v->scope = OutScope;
1214 if (ct == CloseElse) {
1215 /* All Pending variables with this name
1216 * are now Conditional */
1218 v2 && v2->scope == PendingScope;
1220 v2->scope = CondScope;
1225 v2 && v2->scope == PendingScope;
1227 if (v2->val.type != Tlabel)
1228 v2->scope = OutScope;
1230 case OutScope: break;
1233 case CloseSequential:
1234 if (v->val.type == Tlabel)
1235 v->scope = PendingScope;
1238 v->scope = OutScope;
1241 /* There was no 'else', so we can only become
1242 * conditional if we know the cases were exhaustive,
1243 * and that doesn't mean anything yet.
1244 * So only labels become conditional..
1247 v2 && v2->scope == PendingScope;
1249 if (v2->val.type == Tlabel) {
1250 v2->scope = CondScope;
1251 v2->min_depth = c->scope_depth;
1253 v2->scope = OutScope;
1256 case OutScope: break;
1260 if (v->scope == OutScope)
1269 Executables can be lots of different things. In many cases an
1270 executable is just an operation combined with one or two other
1271 executables. This allows for expressions and lists etc. Other times
1272 an executable is something quite specific like a constant or variable
1273 name. So we define a `struct exec` to be a general executable with a
1274 type, and a `struct binode` which is a subclass of `exec`, forms a
1275 node in a binary tree, and holds an operation. There will be other
1276 subclasses, and to access these we need to be able to `cast` the
1277 `exec` into the various other types.
1280 #define cast(structname, pointer) ({ \
1281 const typeof( ((struct structname *)0)->type) *__mptr = &(pointer)->type; \
1282 if (__mptr && *__mptr != X##structname) abort(); \
1283 (struct structname *)( (char *)__mptr);})
1285 #define new(structname) ({ \
1286 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1287 __ptr->type = X##structname; \
1288 __ptr->line = -1; __ptr->column = -1; \
1291 #define new_pos(structname, token) ({ \
1292 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1293 __ptr->type = X##structname; \
1294 __ptr->line = token.line; __ptr->column = token.col; \
1303 enum exec_types type;
1311 struct exec *left, *right;
1314 ###### ast functions
1316 static int __fput_loc(struct exec *loc, FILE *f)
1320 if (loc->line >= 0) {
1321 fprintf(f, "%d:%d: ", loc->line, loc->column);
1324 if (loc->type == Xbinode)
1325 return __fput_loc(cast(binode,loc)->left, f) ||
1326 __fput_loc(cast(binode,loc)->right, f);
1329 static void fput_loc(struct exec *loc, FILE *f)
1331 if (!__fput_loc(loc, f))
1332 fprintf(f, "??:??: "); // NOTEST
1335 Each different type of `exec` node needs a number of functions
1336 defined, a bit like methods. We must be able to be able to free it,
1337 print it, analyse it and execute it. Once we have specific `exec`
1338 types we will need to parse them too. Let's take this a bit more
1343 The parser generator requires a `free_foo` function for each struct
1344 that stores attributes and they will be `exec`s and subtypes there-of.
1345 So we need `free_exec` which can handle all the subtypes, and we need
1348 ###### ast functions
1350 static void free_binode(struct binode *b)
1355 free_exec(b->right);
1359 ###### core functions
1360 static void free_exec(struct exec *e)
1369 ###### forward decls
1371 static void free_exec(struct exec *e);
1373 ###### free exec cases
1374 case Xbinode: free_binode(cast(binode, e)); break;
1378 Printing an `exec` requires that we know the current indent level for
1379 printing line-oriented components. As will become clear later, we
1380 also want to know what sort of bracketing to use.
1382 ###### ast functions
1384 static void do_indent(int i, char *str)
1391 ###### core functions
1392 static void print_binode(struct binode *b, int indent, int bracket)
1396 ## print binode cases
1400 static void print_exec(struct exec *e, int indent, int bracket)
1406 print_binode(cast(binode, e), indent, bracket); break;
1411 ###### forward decls
1413 static void print_exec(struct exec *e, int indent, int bracket);
1417 As discussed, analysis involves propagating type requirements around
1418 the program and looking for errors.
1420 So `propagate_types` is passed an expected type (being a `struct type`
1421 pointer together with some `val_rules` flags) that the `exec` is
1422 expected to return, and returns the type that it does return, either
1423 of which can be `NULL` signifying "unknown". An `ok` flag is passed
1424 by reference. It is set to `0` when an error is found, and `2` when
1425 any change is made. If it remains unchanged at `1`, then no more
1426 propagation is needed.
1430 enum val_rules {Rnolabel = 1<<0, Rboolok = 1<<1, Rnoconstant = 2<<1};
1434 if (rules & Rnolabel)
1435 fputs(" (labels not permitted)", stderr);
1438 ###### core functions
1440 static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1441 struct type *type, int rules)
1448 switch (prog->type) {
1451 struct binode *b = cast(binode, prog);
1453 ## propagate binode cases
1457 ## propagate exec cases
1464 Interpreting an `exec` doesn't require anything but the `exec`. State
1465 is stored in variables and each variable will be directly linked from
1466 within the `exec` tree. The exception to this is the whole `program`
1467 which needs to look at command line arguments. The `program` will be
1468 interpreted separately.
1470 Each `exec` can return a value, which may be `Tnone` but must be non-NULL;
1472 ###### core functions
1475 struct value val, *lval;
1478 static struct lrval _interp_exec(struct exec *e);
1480 static struct value interp_exec(struct exec *e)
1482 struct lrval ret = _interp_exec(e);
1485 return dup_value(*ret.lval);
1490 static struct value *linterp_exec(struct exec *e)
1492 struct lrval ret = _interp_exec(e);
1497 static struct lrval _interp_exec(struct exec *e)
1500 struct value rv, *lrv = NULL;
1511 struct binode *b = cast(binode, e);
1512 struct value left, right, *lleft;
1513 left.type = right.type = Tnone;
1515 ## interp binode cases
1517 free_value(left); free_value(right);
1520 ## interp exec cases
1529 Now that we have the shape of the interpreter in place we can add some
1530 complex types and connected them in to the data structures and the
1531 different phases of parse, analyse, print, interpret.
1533 For now, just arrays.
1537 Arrays can be declared by giving a size and a type, as `[size]type' so
1538 `freq:[26]number` declares `freq` to be an array of 26 numbers. The
1539 size can be an arbitrary expression which is evaluated when the name
1542 Arrays cannot be assigned. When pointers are introduced we will also
1543 introduce array slices which can refer to part or all of an array -
1544 the assignment syntax will create a slice. For now, an array can only
1545 ever be referenced by the name it is declared with. It is likely that
1546 a "`copy`" primitive will eventually be define which can be used to
1547 make a copy of an array with controllable depth.
1549 ###### type union fields
1553 struct variable *vsize;
1554 struct type *member;
1557 ###### value union fields
1559 struct value *elmnts;
1562 ###### value functions
1564 static struct value array_prepare(struct type *type)
1569 ret.array.elmnts = NULL;
1573 static struct value array_init(struct type *type)
1579 if (type->array.vsize) {
1582 mpz_tdiv_q(q, mpq_numref(type->array.vsize->val.num),
1583 mpq_denref(type->array.vsize->val.num));
1584 type->array.size = mpz_get_si(q);
1587 ret.array.elmnts = calloc(type->array.size,
1588 sizeof(ret.array.elmnts[0]));
1589 for (i = 0; ret.array.elmnts && i < type->array.size; i++)
1590 ret.array.elmnts[i] = val_init(type->array.member);
1594 static void array_free(struct value val)
1598 if (val.array.elmnts)
1599 for (i = 0; i < val.type->array.size; i++)
1600 free_value(val.array.elmnts[i]);
1601 free(val.array.elmnts);
1604 static int array_compat(struct type *require, struct type *have)
1606 if (have->compat != require->compat)
1608 /* Both are arrays, so we can look at details */
1609 if (!type_compat(require->array.member, have->array.member, 0))
1611 if (require->array.vsize == NULL && have->array.vsize == NULL)
1612 return require->array.size == have->array.size;
1614 return require->array.vsize == have->array.vsize;
1617 static void array_print_type(struct type *type, FILE *f)
1620 if (type->array.vsize) {
1621 struct binding *b = type->array.vsize->name;
1622 fprintf(f, "%.*s]", b->name.len, b->name.txt);
1624 fprintf(f, "%d]", type->array.size);
1625 type_print(type->array.member, f);
1628 static struct type array_prototype = {
1629 .prepare = array_prepare,
1631 .print_type = array_print_type,
1632 .compat = array_compat,
1638 | [ NUMBER ] Type ${
1639 $0 = calloc(1, sizeof(struct type));
1640 *($0) = array_prototype;
1641 $0->array.member = $<4;
1642 $0->array.vsize = NULL;
1644 struct parse_context *c = config2context(config);
1647 if (number_parse(num, tail, $2.txt) == 0)
1648 tok_err(c, "error: unrecognised number", &$2);
1650 tok_err(c, "error: unsupported number suffix", &$2);
1652 $0->array.size = mpz_get_ui(mpq_numref(num));
1653 if (mpz_cmp_ui(mpq_denref(num), 1) != 0) {
1654 tok_err(c, "error: array size must be an integer",
1656 } else if (mpz_cmp_ui(mpq_numref(num), 1UL << 30) >= 0)
1657 tok_err(c, "error: array size is too large",
1661 $0->next= c->anon_typelist;
1662 c->anon_typelist = $0;
1666 | [ IDENTIFIER ] Type ${ {
1667 struct parse_context *c = config2context(config);
1668 struct variable *v = var_ref(c, $2.txt);
1671 tok_err(config2context(config), "error: name undeclared", &$2);
1672 else if (!v->constant)
1673 tok_err(config2context(config), "error: array size must be a constant", &$2);
1675 $0 = calloc(1, sizeof(struct type));
1676 *($0) = array_prototype;
1677 $0->array.member = $<4;
1679 $0->array.vsize = v;
1680 $0->next= c->anon_typelist;
1681 c->anon_typelist = $0;
1684 ###### parse context
1686 struct type *anon_typelist;
1688 ###### free context types
1690 while (context.anon_typelist) {
1691 struct type *t = context.anon_typelist;
1693 context.anon_typelist = t->next;
1700 ###### variable grammar
1702 | Variable [ Expression ] ${ {
1703 struct binode *b = new(binode);
1710 ###### print binode cases
1712 print_exec(b->left, -1, 0);
1714 print_exec(b->right, -1, 0);
1718 ###### propagate binode cases
1720 /* left must be an array, right must be a number,
1721 * result is the member type of the array
1723 propagate_types(b->right, c, ok, Tnum, 0);
1724 t = propagate_types(b->left, c, ok, NULL, rules & Rnoconstant);
1725 if (!t || t->compat != array_compat) {
1726 type_err(c, "error: %1 cannot be indexed", prog, t, 0, NULL);
1730 if (!type_compat(type, t->array.member, rules)) {
1731 type_err(c, "error: have %1 but need %2", prog,
1732 t->array.member, rules, type);
1735 return t->array.member;
1739 ###### interp binode cases
1744 lleft = linterp_exec(b->left);
1745 right = interp_exec(b->right);
1747 mpz_tdiv_q(q, mpq_numref(right.num), mpq_denref(right.num));
1751 if (i >= 0 && i < lleft->type->array.size)
1752 lrv = &lleft->array.elmnts[i];
1754 rv = val_init(lleft->type->array.member);
1758 ## Language elements
1760 Each language element needs to be parsed, printed, analysed,
1761 interpreted, and freed. There are several, so let's just start with
1762 the easy ones and work our way up.
1766 We have already met values as separate objects. When manifest
1767 constants appear in the program text, that must result in an executable
1768 which has a constant value. So the `val` structure embeds a value in
1784 $0 = new_pos(val, $1);
1785 $0->val.type = Tbool;
1789 $0 = new_pos(val, $1);
1790 $0->val.type = Tbool;
1794 $0 = new_pos(val, $1);
1795 $0->val.type = Tnum;
1798 if (number_parse($0->val.num, tail, $1.txt) == 0)
1799 mpq_init($0->val.num);
1801 tok_err(config2context(config), "error: unsupported number suffix",
1806 $0 = new_pos(val, $1);
1807 $0->val.type = Tstr;
1810 string_parse(&$1, '\\', &$0->val.str, tail);
1812 tok_err(config2context(config), "error: unsupported string suffix",
1817 $0 = new_pos(val, $1);
1818 $0->val.type = Tstr;
1821 string_parse(&$1, '\\', &$0->val.str, tail);
1823 tok_err(config2context(config), "error: unsupported string suffix",
1828 ###### print exec cases
1831 struct val *v = cast(val, e);
1832 if (v->val.type == Tstr)
1834 print_value(v->val);
1835 if (v->val.type == Tstr)
1840 ###### propagate exec cases
1843 struct val *val = cast(val, prog);
1844 if (!type_compat(type, val->val.type, rules)) {
1845 type_err(c, "error: expected %1%r found %2",
1846 prog, type, rules, val->val.type);
1849 return val->val.type;
1852 ###### interp exec cases
1854 rv = dup_value(cast(val, e)->val);
1857 ###### ast functions
1858 static void free_val(struct val *v)
1866 ###### free exec cases
1867 case Xval: free_val(cast(val, e)); break;
1869 ###### ast functions
1870 // Move all nodes from 'b' to 'rv', reversing the order.
1871 // In 'b' 'left' is a list, and 'right' is the last node.
1872 // In 'rv', left' is the first node and 'right' is a list.
1873 static struct binode *reorder_bilist(struct binode *b)
1875 struct binode *rv = NULL;
1878 struct exec *t = b->right;
1882 b = cast(binode, b->left);
1892 Just as we used a `val` to wrap a value into an `exec`, we similarly
1893 need a `var` to wrap a `variable` into an exec. While each `val`
1894 contained a copy of the value, each `var` hold a link to the variable
1895 because it really is the same variable no matter where it appears.
1896 When a variable is used, we need to remember to follow the `->merged`
1897 link to find the primary instance.
1905 struct variable *var;
1911 VariableDecl -> IDENTIFIER : ${ {
1912 struct variable *v = var_decl(config2context(config), $1.txt);
1913 $0 = new_pos(var, $1);
1918 v = var_ref(config2context(config), $1.txt);
1920 type_err(config2context(config), "error: variable '%v' redeclared",
1921 $0, Tnone, 0, Tnone);
1922 type_err(config2context(config), "info: this is where '%v' was first declared",
1923 v->where_decl, Tnone, 0, Tnone);
1926 | IDENTIFIER :: ${ {
1927 struct variable *v = var_decl(config2context(config), $1.txt);
1928 $0 = new_pos(var, $1);
1934 v = var_ref(config2context(config), $1.txt);
1936 type_err(config2context(config), "error: variable '%v' redeclared",
1937 $0, Tnone, 0, Tnone);
1938 type_err(config2context(config), "info: this is where '%v' was first declared",
1939 v->where_decl, Tnone, 0, Tnone);
1942 | IDENTIFIER : Type ${ {
1943 struct variable *v = var_decl(config2context(config), $1.txt);
1944 $0 = new_pos(var, $1);
1949 v->val = val_prepare($<3);
1951 v = var_ref(config2context(config), $1.txt);
1953 type_err(config2context(config), "error: variable '%v' redeclared",
1954 $0, Tnone, 0, Tnone);
1955 type_err(config2context(config), "info: this is where '%v' was first declared",
1956 v->where_decl, Tnone, 0, Tnone);
1959 | IDENTIFIER :: Type ${ {
1960 struct variable *v = var_decl(config2context(config), $1.txt);
1961 $0 = new_pos(var, $1);
1966 v->val = val_prepare($<3);
1969 v = var_ref(config2context(config), $1.txt);
1971 type_err(config2context(config), "error: variable '%v' redeclared",
1972 $0, Tnone, 0, Tnone);
1973 type_err(config2context(config), "info: this is where '%v' was first declared",
1974 v->where_decl, Tnone, 0, Tnone);
1979 Variable -> IDENTIFIER ${ {
1980 struct variable *v = var_ref(config2context(config), $1.txt);
1981 $0 = new_pos(var, $1);
1983 /* This might be a label - allocate a var just in case */
1984 v = var_decl(config2context(config), $1.txt);
1986 v->val = val_prepare(Tlabel);
1987 v->val.label = &v->val;
1991 cast(var, $0)->var = v;
1996 Type -> IDENTIFIER ${
1997 $0 = find_type(config2context(config), $1.txt);
1999 tok_err(config2context(config),
2000 "error: undefined type", &$1);
2007 ###### print exec cases
2010 struct var *v = cast(var, e);
2012 struct binding *b = v->var->name;
2013 printf("%.*s", b->name.len, b->name.txt);
2020 if (loc->type == Xvar) {
2021 struct var *v = cast(var, loc);
2023 struct binding *b = v->var->name;
2024 fprintf(stderr, "%.*s", b->name.len, b->name.txt);
2026 fputs("???", stderr); // NOTEST
2028 fputs("NOTVAR", stderr); // NOTEST
2031 ###### propagate exec cases
2035 struct var *var = cast(var, prog);
2036 struct variable *v = var->var;
2038 type_err(c, "%d:BUG: no variable!!", prog, Tnone, 0, Tnone); // NOTEST
2040 return Tnone; // NOTEST
2044 if (v->constant && (rules & Rnoconstant)) {
2045 type_err(c, "error: Cannot assign to a constant: %v",
2046 prog, NULL, 0, NULL);
2047 type_err(c, "info: name was defined as a constant here",
2048 v->where_decl, NULL, 0, NULL);
2052 if (v->val.type == NULL) {
2053 if (type && *ok != 0) {
2054 v->val = val_prepare(type);
2055 v->where_set = prog;
2060 if (!type_compat(type, v->val.type, rules)) {
2061 type_err(c, "error: expected %1%r but variable '%v' is %2", prog,
2062 type, rules, v->val.type);
2063 type_err(c, "info: this is where '%v' was set to %1", v->where_set,
2064 v->val.type, rules, Tnone);
2072 ###### interp exec cases
2075 struct var *var = cast(var, e);
2076 struct variable *v = var->var;
2084 ###### ast functions
2086 static void free_var(struct var *v)
2091 ###### free exec cases
2092 case Xvar: free_var(cast(var, e)); break;
2094 ### Expressions: Conditional
2096 Our first user of the `binode` will be conditional expressions, which
2097 is a bit odd as they actually have three components. That will be
2098 handled by having 2 binodes for each expression. The conditional
2099 expression is the lowest precedence operatior, so it gets to define
2100 what an "Expression" is. The next level up is "BoolExpr", which
2103 Conditional expressions are of the form "value `if` condition `else`
2104 other_value". There is no associativite with this operator: the
2105 values and conditions can only be other conditional expressions if
2106 they are enclosed in parentheses. Allowing nesting without
2107 parentheses would be too confusing.
2115 Expression -> BoolExpr if BoolExpr else BoolExpr ${ {
2116 struct binode *b1 = new(binode);
2117 struct binode *b2 = new(binode);
2126 | BoolExpr ${ $0 = $<1; }$
2128 ###### print binode cases
2131 b2 = cast(binode, b->right);
2132 print_exec(b2->left, -1, 0);
2134 print_exec(b->left, -1, 0);
2136 print_exec(b2->right, -1, 0);
2139 ###### propagate binode cases
2142 /* cond must be Tbool, others must match */
2143 struct binode *b2 = cast(binode, b->right);
2146 propagate_types(b->left, c, ok, Tbool, 0);
2147 t = propagate_types(b2->left, c, ok, type, Rnolabel);
2148 t2 = propagate_types(b2->right, c, ok, type ?: t, Rnolabel);
2152 ###### interp binode cases
2155 struct binode *b2 = cast(binode, b->right);
2156 left = interp_exec(b->left);
2158 rv = interp_exec(b2->left);
2160 rv = interp_exec(b2->right);
2164 ### Expressions: Boolean
2166 The next class of expressions to use the `binode` will be Boolean
2167 expressions. As I haven't implemented precedence in the parser
2168 generator yet, we need different names for each precedence level used
2169 by expressions. The outer most or lowest level precedence are
2170 conditional expressions are Boolean operators which form an `BoolExpr`
2171 out of `BTerm`s and `BFact`s. As well as `or` `and`, and `not` we
2172 have `and then` and `or else` which only evaluate the second operand
2173 if the result would make a difference.
2185 BoolExpr -> BoolExpr or BTerm ${ {
2186 struct binode *b = new(binode);
2192 | BoolExpr or else BTerm ${ {
2193 struct binode *b = new(binode);
2199 | BTerm ${ $0 = $<1; }$
2201 BTerm -> BTerm and BFact ${ {
2202 struct binode *b = new(binode);
2208 | BTerm and then BFact ${ {
2209 struct binode *b = new(binode);
2215 | BFact ${ $0 = $<1; }$
2217 BFact -> not BFact ${ {
2218 struct binode *b = new(binode);
2225 ###### print binode cases
2227 print_exec(b->left, -1, 0);
2229 print_exec(b->right, -1, 0);
2232 print_exec(b->left, -1, 0);
2233 printf(" and then ");
2234 print_exec(b->right, -1, 0);
2237 print_exec(b->left, -1, 0);
2239 print_exec(b->right, -1, 0);
2242 print_exec(b->left, -1, 0);
2243 printf(" or else ");
2244 print_exec(b->right, -1, 0);
2248 print_exec(b->right, -1, 0);
2251 ###### propagate binode cases
2257 /* both must be Tbool, result is Tbool */
2258 propagate_types(b->left, c, ok, Tbool, 0);
2259 propagate_types(b->right, c, ok, Tbool, 0);
2260 if (type && type != Tbool) {
2261 type_err(c, "error: %1 operation found where %2 expected", prog,
2267 ###### interp binode cases
2269 rv = interp_exec(b->left);
2270 right = interp_exec(b->right);
2271 rv.bool = rv.bool && right.bool;
2274 rv = interp_exec(b->left);
2276 rv = interp_exec(b->right);
2279 rv = interp_exec(b->left);
2280 right = interp_exec(b->right);
2281 rv.bool = rv.bool || right.bool;
2284 rv = interp_exec(b->left);
2286 rv = interp_exec(b->right);
2289 rv = interp_exec(b->right);
2293 ### Expressions: Comparison
2295 Of slightly higher precedence that Boolean expressions are
2297 A comparison takes arguments of any type, but the two types must be
2300 To simplify the parsing we introduce an `eop` which can record an
2301 expression operator.
2308 ###### ast functions
2309 static void free_eop(struct eop *e)
2324 | Expr CMPop Expr ${ {
2325 struct binode *b = new(binode);
2331 | Expr ${ $0 = $<1; }$
2336 CMPop -> < ${ $0.op = Less; }$
2337 | > ${ $0.op = Gtr; }$
2338 | <= ${ $0.op = LessEq; }$
2339 | >= ${ $0.op = GtrEq; }$
2340 | == ${ $0.op = Eql; }$
2341 | != ${ $0.op = NEql; }$
2343 ###### print binode cases
2351 print_exec(b->left, -1, 0);
2353 case Less: printf(" < "); break;
2354 case LessEq: printf(" <= "); break;
2355 case Gtr: printf(" > "); break;
2356 case GtrEq: printf(" >= "); break;
2357 case Eql: printf(" == "); break;
2358 case NEql: printf(" != "); break;
2359 default: abort(); // NOTEST
2361 print_exec(b->right, -1, 0);
2364 ###### propagate binode cases
2371 /* Both must match but not be labels, result is Tbool */
2372 t = propagate_types(b->left, c, ok, NULL, Rnolabel);
2374 propagate_types(b->right, c, ok, t, 0);
2376 t = propagate_types(b->right, c, ok, NULL, Rnolabel);
2378 t = propagate_types(b->left, c, ok, t, 0);
2380 if (!type_compat(type, Tbool, 0)) {
2381 type_err(c, "error: Comparison returns %1 but %2 expected", prog,
2382 Tbool, rules, type);
2387 ###### interp binode cases
2396 left = interp_exec(b->left);
2397 right = interp_exec(b->right);
2398 cmp = value_cmp(left, right);
2401 case Less: rv.bool = cmp < 0; break;
2402 case LessEq: rv.bool = cmp <= 0; break;
2403 case Gtr: rv.bool = cmp > 0; break;
2404 case GtrEq: rv.bool = cmp >= 0; break;
2405 case Eql: rv.bool = cmp == 0; break;
2406 case NEql: rv.bool = cmp != 0; break;
2407 default: rv.bool = 0; break; // NOTEST
2412 ### Expressions: The rest
2414 The remaining expressions with the highest precedence are arithmetic
2415 and string concatenation. They are `Expr`, `Term`, and `Factor`.
2416 The `Factor` is where the `Value` and `Variable` that we already have
2419 `+` and `-` are both infix and prefix operations (where they are
2420 absolute value and negation). These have different operator names.
2422 We also have a 'Bracket' operator which records where parentheses were
2423 found. This makes it easy to reproduce these when printing. Once
2424 precedence is handled better I might be able to discard this.
2436 Expr -> Expr Eop Term ${ {
2437 struct binode *b = new(binode);
2443 | Term ${ $0 = $<1; }$
2445 Term -> Term Top Factor ${ {
2446 struct binode *b = new(binode);
2452 | Factor ${ $0 = $<1; }$
2454 Factor -> ( Expression ) ${ {
2455 struct binode *b = new_pos(binode, $1);
2461 struct binode *b = new(binode);
2466 | Value ${ $0 = $<1; }$
2467 | Variable ${ $0 = $<1; }$
2470 Eop -> + ${ $0.op = Plus; }$
2471 | - ${ $0.op = Minus; }$
2473 Uop -> + ${ $0.op = Absolute; }$
2474 | - ${ $0.op = Negate; }$
2476 Top -> * ${ $0.op = Times; }$
2477 | / ${ $0.op = Divide; }$
2478 | % ${ $0.op = Rem; }$
2479 | ++ ${ $0.op = Concat; }$
2481 ###### print binode cases
2488 print_exec(b->left, indent, 0);
2490 case Plus: fputs(" + ", stdout); break;
2491 case Minus: fputs(" - ", stdout); break;
2492 case Times: fputs(" * ", stdout); break;
2493 case Divide: fputs(" / ", stdout); break;
2494 case Rem: fputs(" % ", stdout); break;
2495 case Concat: fputs(" ++ ", stdout); break;
2496 default: abort(); // NOTEST
2498 print_exec(b->right, indent, 0);
2502 print_exec(b->right, indent, 0);
2506 print_exec(b->right, indent, 0);
2510 print_exec(b->right, indent, 0);
2514 ###### propagate binode cases
2520 /* both must be numbers, result is Tnum */
2523 /* as propagate_types ignores a NULL,
2524 * unary ops fit here too */
2525 propagate_types(b->left, c, ok, Tnum, 0);
2526 propagate_types(b->right, c, ok, Tnum, 0);
2527 if (!type_compat(type, Tnum, 0)) {
2528 type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
2535 /* both must be Tstr, result is Tstr */
2536 propagate_types(b->left, c, ok, Tstr, 0);
2537 propagate_types(b->right, c, ok, Tstr, 0);
2538 if (!type_compat(type, Tstr, 0)) {
2539 type_err(c, "error: Concat returns %1 but %2 expected", prog,
2546 return propagate_types(b->right, c, ok, type, 0);
2548 ###### interp binode cases
2551 rv = interp_exec(b->left);
2552 right = interp_exec(b->right);
2553 mpq_add(rv.num, rv.num, right.num);
2556 rv = interp_exec(b->left);
2557 right = interp_exec(b->right);
2558 mpq_sub(rv.num, rv.num, right.num);
2561 rv = interp_exec(b->left);
2562 right = interp_exec(b->right);
2563 mpq_mul(rv.num, rv.num, right.num);
2566 rv = interp_exec(b->left);
2567 right = interp_exec(b->right);
2568 mpq_div(rv.num, rv.num, right.num);
2573 left = interp_exec(b->left);
2574 right = interp_exec(b->right);
2575 mpz_init(l); mpz_init(r); mpz_init(rem);
2576 mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
2577 mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
2578 mpz_tdiv_r(rem, l, r);
2579 rv = val_init(Tnum);
2580 mpq_set_z(rv.num, rem);
2581 mpz_clear(r); mpz_clear(l); mpz_clear(rem);
2585 rv = interp_exec(b->right);
2586 mpq_neg(rv.num, rv.num);
2589 rv = interp_exec(b->right);
2590 mpq_abs(rv.num, rv.num);
2593 rv = interp_exec(b->right);
2596 left = interp_exec(b->left);
2597 right = interp_exec(b->right);
2599 rv.str = text_join(left.str, right.str);
2603 ###### value functions
2605 static struct text text_join(struct text a, struct text b)
2608 rv.len = a.len + b.len;
2609 rv.txt = malloc(rv.len);
2610 memcpy(rv.txt, a.txt, a.len);
2611 memcpy(rv.txt+a.len, b.txt, b.len);
2616 ### Blocks, Statements, and Statement lists.
2618 Now that we have expressions out of the way we need to turn to
2619 statements. There are simple statements and more complex statements.
2620 Simple statements do not contain newlines, complex statements do.
2622 Statements often come in sequences and we have corresponding simple
2623 statement lists and complex statement lists.
2624 The former comprise only simple statements separated by semicolons.
2625 The later comprise complex statements and simple statement lists. They are
2626 separated by newlines. Thus the semicolon is only used to separate
2627 simple statements on the one line. This may be overly restrictive,
2628 but I'm not sure I ever want a complex statement to share a line with
2631 Note that a simple statement list can still use multiple lines if
2632 subsequent lines are indented, so
2634 ###### Example: wrapped simple statement list
2639 is a single simple statement list. This might allow room for
2640 confusion, so I'm not set on it yet.
2642 A simple statement list needs no extra syntax. A complex statement
2643 list has two syntactic forms. It can be enclosed in braces (much like
2644 C blocks), or it can be introduced by a colon and continue until an
2645 unindented newline (much like Python blocks). With this extra syntax
2646 it is referred to as a block.
2648 Note that a block does not have to include any newlines if it only
2649 contains simple statements. So both of:
2651 if condition: a=b; d=f
2653 if condition { a=b; print f }
2657 In either case the list is constructed from a `binode` list with
2658 `Block` as the operator. When parsing the list it is most convenient
2659 to append to the end, so a list is a list and a statement. When using
2660 the list it is more convenient to consider a list to be a statement
2661 and a list. So we need a function to re-order a list.
2662 `reorder_bilist` serves this purpose.
2664 The only stand-alone statement we introduce at this stage is `pass`
2665 which does nothing and is represented as a `NULL` pointer in a `Block`
2666 list. Other stand-alone statements will follow once the infrastructure
2686 Block -> Open Statementlist Close ${ $0 = $<2; }$
2687 | Open Newlines Statementlist Close ${ $0 = $<3; }$
2688 | Open SimpleStatements } ${ $0 = reorder_bilist($<2); }$
2689 | Open Newlines SimpleStatements } ${ $0 = reorder_bilist($<3); }$
2690 | : Statementlist ${ $0 = $<2; }$
2691 | : SimpleStatements ${ $0 = reorder_bilist($<2); }$
2693 Statementlist -> ComplexStatements ${ $0 = reorder_bilist($<1); }$
2695 ComplexStatements -> ComplexStatements ComplexStatement ${
2701 | ComplexStatements NEWLINE ${ $0 = $<1; }$
2702 | ComplexStatement ${
2710 ComplexStatement -> SimpleStatements NEWLINE ${
2711 $0 = reorder_bilist($<1);
2713 ## ComplexStatement Grammar
2716 SimpleStatements -> SimpleStatements ; SimpleStatement ${
2722 | SimpleStatement ${
2728 | SimpleStatements ; ${ $0 = $<1; }$
2730 SimpleStatement -> pass ${ $0 = NULL; }$
2731 ## SimpleStatement Grammar
2733 ###### print binode cases
2737 if (b->left == NULL)
2740 print_exec(b->left, indent, 0);
2743 print_exec(b->right, indent, 0);
2746 // block, one per line
2747 if (b->left == NULL)
2748 do_indent(indent, "pass\n");
2750 print_exec(b->left, indent, bracket);
2752 print_exec(b->right, indent, bracket);
2756 ###### propagate binode cases
2759 /* If any statement returns something other than Tnone
2760 * or Tbool then all such must return same type.
2761 * As each statement may be Tnone or something else,
2762 * we must always pass NULL (unknown) down, otherwise an incorrect
2763 * error might occur. We never return Tnone unless it is
2768 for (e = b; e; e = cast(binode, e->right)) {
2769 t = propagate_types(e->left, c, ok, NULL, rules);
2770 if ((rules & Rboolok) && t == Tbool)
2772 if (t && t != Tnone && t != Tbool) {
2775 else if (t != type) {
2776 type_err(c, "error: expected %1%r, found %2",
2777 e->left, type, rules, t);
2785 ###### interp binode cases
2787 while (rv.type == Tnone &&
2790 rv = interp_exec(b->left);
2791 b = cast(binode, b->right);
2795 ### The Print statement
2797 `print` is a simple statement that takes a comma-separated list of
2798 expressions and prints the values separated by spaces and terminated
2799 by a newline. No control of formatting is possible.
2801 `print` faces the same list-ordering issue as blocks, and uses the
2807 ###### SimpleStatement Grammar
2809 | print ExpressionList ${
2810 $0 = reorder_bilist($<2);
2812 | print ExpressionList , ${
2817 $0 = reorder_bilist($0);
2828 ExpressionList -> ExpressionList , Expression ${
2841 ###### print binode cases
2844 do_indent(indent, "print");
2848 print_exec(b->left, -1, 0);
2852 b = cast(binode, b->right);
2858 ###### propagate binode cases
2861 /* don't care but all must be consistent */
2862 propagate_types(b->left, c, ok, NULL, Rnolabel);
2863 propagate_types(b->right, c, ok, NULL, Rnolabel);
2866 ###### interp binode cases
2872 for ( ; b; b = cast(binode, b->right))
2876 left = interp_exec(b->left);
2889 ###### Assignment statement
2891 An assignment will assign a value to a variable, providing it hasn't
2892 be declared as a constant. The analysis phase ensures that the type
2893 will be correct so the interpreter just needs to perform the
2894 calculation. There is a form of assignment which declares a new
2895 variable as well as assigning a value. If a name is assigned before
2896 it is declared, and error will be raised as the name is created as
2897 `Tlabel` and it is illegal to assign to such names.
2903 ###### SimpleStatement Grammar
2904 | Variable = Expression ${
2910 | VariableDecl = Expression ${
2918 if ($1->var->where_set == NULL) {
2919 type_err(config2context(config), "Variable declared with no type or value: %v",
2929 ###### print binode cases
2932 do_indent(indent, "");
2933 print_exec(b->left, indent, 0);
2935 print_exec(b->right, indent, 0);
2942 struct variable *v = cast(var, b->left)->var;
2943 do_indent(indent, "");
2944 print_exec(b->left, indent, 0);
2945 if (cast(var, b->left)->var->constant) {
2946 if (v->where_decl == v->where_set) {
2948 type_print(v->val.type, stdout);
2953 if (v->where_decl == v->where_set) {
2955 type_print(v->val.type, stdout);
2962 print_exec(b->right, indent, 0);
2969 ###### propagate binode cases
2973 /* Both must match and not be labels,
2974 * Type must support 'dup',
2975 * For Assign, left must not be constant.
2978 t = propagate_types(b->left, c, ok, NULL,
2979 Rnolabel | (b->op == Assign ? Rnoconstant : 0));
2984 if (propagate_types(b->right, c, ok, t, 0) != t)
2985 if (b->left->type == Xvar)
2986 type_err(c, "info: variable '%v' was set as %1 here.",
2987 cast(var, b->left)->var->where_set, t, rules, Tnone);
2989 t = propagate_types(b->right, c, ok, NULL, Rnolabel);
2991 propagate_types(b->left, c, ok, t,
2992 (b->op == Assign ? Rnoconstant : 0));
2994 if (t && t->dup == NULL) {
2995 type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
3002 ###### interp binode cases
3005 lleft = linterp_exec(b->left);
3006 right = interp_exec(b->right);
3011 free_value(right); // NOTEST
3017 struct variable *v = cast(var, b->left)->var;
3021 right = interp_exec(b->right);
3023 right = val_init(v->val.type);
3030 ### The `use` statement
3032 The `use` statement is the last "simple" statement. It is needed when
3033 the condition in a conditional statement is a block. `use` works much
3034 like `return` in C, but only completes the `condition`, not the whole
3040 ###### SimpleStatement Grammar
3042 $0 = new_pos(binode, $1);
3047 ###### print binode cases
3050 do_indent(indent, "use ");
3051 print_exec(b->right, -1, 0);
3056 ###### propagate binode cases
3059 /* result matches value */
3060 return propagate_types(b->right, c, ok, type, 0);
3062 ###### interp binode cases
3065 rv = interp_exec(b->right);
3068 ### The Conditional Statement
3070 This is the biggy and currently the only complex statement. This
3071 subsumes `if`, `while`, `do/while`, `switch`, and some parts of `for`.
3072 It is comprised of a number of parts, all of which are optional though
3073 set combinations apply. Each part is (usually) a key word (`then` is
3074 sometimes optional) followed by either an expression or a code block,
3075 except the `casepart` which is a "key word and an expression" followed
3076 by a code block. The code-block option is valid for all parts and,
3077 where an expression is also allowed, the code block can use the `use`
3078 statement to report a value. If the code block does not report a value
3079 the effect is similar to reporting `True`.
3081 The `else` and `case` parts, as well as `then` when combined with
3082 `if`, can contain a `use` statement which will apply to some
3083 containing conditional statement. `for` parts, `do` parts and `then`
3084 parts used with `for` can never contain a `use`, except in some
3085 subordinate conditional statement.
3087 If there is a `forpart`, it is executed first, only once.
3088 If there is a `dopart`, then it is executed repeatedly providing
3089 always that the `condpart` or `cond`, if present, does not return a non-True
3090 value. `condpart` can fail to return any value if it simply executes
3091 to completion. This is treated the same as returning `True`.
3093 If there is a `thenpart` it will be executed whenever the `condpart`
3094 or `cond` returns True (or does not return any value), but this will happen
3095 *after* `dopart` (when present).
3097 If `elsepart` is present it will be executed at most once when the
3098 condition returns `False` or some value that isn't `True` and isn't
3099 matched by any `casepart`. If there are any `casepart`s, they will be
3100 executed when the condition returns a matching value.
3102 The particular sorts of values allowed in case parts has not yet been
3103 determined in the language design, so nothing is prohibited.
3105 The various blocks in this complex statement potentially provide scope
3106 for variables as described earlier. Each such block must include the
3107 "OpenScope" nonterminal before parsing the block, and must call
3108 `var_block_close()` when closing the block.
3110 The code following "`if`", "`switch`" and "`for`" does not get its own
3111 scope, but is in a scope covering the whole statement, so names
3112 declared there cannot be redeclared elsewhere. Similarly the
3113 condition following "`while`" is in a scope the covers the body
3114 ("`do`" part) of the loop, and which does not allow conditional scope
3115 extension. Code following "`then`" (both looping and non-looping),
3116 "`else`" and "`case`" each get their own local scope.
3118 The type requirements on the code block in a `whilepart` are quite
3119 unusal. It is allowed to return a value of some identifiable type, in
3120 which case the loop aborts and an appropriate `casepart` is run, or it
3121 can return a Boolean, in which case the loop either continues to the
3122 `dopart` (on `True`) or aborts and runs the `elsepart` (on `False`).
3123 This is different both from the `ifpart` code block which is expected to
3124 return a Boolean, or the `switchpart` code block which is expected to
3125 return the same type as the casepart values. The correct analysis of
3126 the type of the `whilepart` code block is the reason for the
3127 `Rboolok` flag which is passed to `propagate_types()`.
3129 The `cond_statement` cannot fit into a `binode` so a new `exec` is
3138 struct exec *action;
3139 struct casepart *next;
3141 struct cond_statement {
3143 struct exec *forpart, *condpart, *dopart, *thenpart, *elsepart;
3144 struct casepart *casepart;
3147 ###### ast functions
3149 static void free_casepart(struct casepart *cp)
3153 free_exec(cp->value);
3154 free_exec(cp->action);
3161 static void free_cond_statement(struct cond_statement *s)
3165 free_exec(s->forpart);
3166 free_exec(s->condpart);
3167 free_exec(s->dopart);
3168 free_exec(s->thenpart);
3169 free_exec(s->elsepart);
3170 free_casepart(s->casepart);
3174 ###### free exec cases
3175 case Xcond_statement: free_cond_statement(cast(cond_statement, e)); break;
3177 ###### ComplexStatement Grammar
3178 | CondStatement ${ $0 = $<1; }$
3183 // both ForThen and Whilepart open scopes, and CondSuffix only
3184 // closes one - so in the first branch here we have another to close.
3185 CondStatement -> ForThen WhilePart CondSuffix ${
3187 $0->forpart = $1.forpart; $1.forpart = NULL;
3188 $0->thenpart = $1.thenpart; $1.thenpart = NULL;
3189 $0->condpart = $2.condpart; $2.condpart = NULL;
3190 $0->dopart = $2.dopart; $2.dopart = NULL;
3191 var_block_close(config2context(config), CloseSequential);
3193 | WhilePart CondSuffix ${
3195 $0->condpart = $1.condpart; $1.condpart = NULL;
3196 $0->dopart = $1.dopart; $1.dopart = NULL;
3198 | SwitchPart CondSuffix ${
3202 | IfPart IfSuffix ${
3204 $0->condpart = $1.condpart; $1.condpart = NULL;
3205 $0->thenpart = $1.thenpart; $1.thenpart = NULL;
3206 // This is where we close an "if" statement
3207 var_block_close(config2context(config), CloseSequential);
3210 CondSuffix -> IfSuffix ${
3212 // This is where we close scope of the whole
3213 // "for" or "while" statement
3214 var_block_close(config2context(config), CloseSequential);
3216 | CasePart CondSuffix ${
3218 $1->next = $0->casepart;
3223 CasePart -> Newlines case Expression OpenScope Block ${
3224 $0 = calloc(1,sizeof(struct casepart));
3227 var_block_close(config2context(config), CloseParallel);
3229 | case Expression OpenScope Block ${
3230 $0 = calloc(1,sizeof(struct casepart));
3233 var_block_close(config2context(config), CloseParallel);
3237 IfSuffix -> Newlines ${ $0 = new(cond_statement); }$
3238 | Newlines else OpenScope Block ${
3239 $0 = new(cond_statement);
3241 var_block_close(config2context(config), CloseElse);
3243 | else OpenScope Block ${
3244 $0 = new(cond_statement);
3246 var_block_close(config2context(config), CloseElse);
3248 | Newlines else OpenScope CondStatement ${
3249 $0 = new(cond_statement);
3251 var_block_close(config2context(config), CloseElse);
3253 | else OpenScope CondStatement ${
3254 $0 = new(cond_statement);
3256 var_block_close(config2context(config), CloseElse);
3261 // These scopes are closed in CondSuffix
3262 ForPart -> for OpenScope SimpleStatements ${
3263 $0 = reorder_bilist($<3);
3265 | for OpenScope Block ${
3269 ThenPart -> then OpenScope SimpleStatements ${
3270 $0 = reorder_bilist($<3);
3271 var_block_close(config2context(config), CloseSequential);
3273 | then OpenScope Block ${
3275 var_block_close(config2context(config), CloseSequential);
3278 ThenPartNL -> ThenPart OptNL ${
3282 // This scope is closed in CondSuffix
3283 WhileHead -> while OpenScope Block ${
3288 ForThen -> ForPart OptNL ThenPartNL ${
3296 // This scope is closed in CondSuffix
3297 WhilePart -> while OpenScope Expression Block ${
3298 $0.type = Xcond_statement;
3302 | WhileHead OptNL do Block ${
3303 $0.type = Xcond_statement;
3308 IfPart -> if OpenScope Expression OpenScope Block ${
3309 $0.type = Xcond_statement;
3312 var_block_close(config2context(config), CloseParallel);
3314 | if OpenScope Block OptNL then OpenScope Block ${
3315 $0.type = Xcond_statement;
3318 var_block_close(config2context(config), CloseParallel);
3322 // This scope is closed in CondSuffix
3323 SwitchPart -> switch OpenScope Expression ${
3326 | switch OpenScope Block ${
3330 ###### print exec cases
3332 case Xcond_statement:
3334 struct cond_statement *cs = cast(cond_statement, e);
3335 struct casepart *cp;
3337 do_indent(indent, "for");
3338 if (bracket) printf(" {\n"); else printf(":\n");
3339 print_exec(cs->forpart, indent+1, bracket);
3342 do_indent(indent, "} then {\n");
3344 do_indent(indent, "then:\n");
3345 print_exec(cs->thenpart, indent+1, bracket);
3347 if (bracket) do_indent(indent, "}\n");
3351 if (cs->condpart && cs->condpart->type == Xbinode &&
3352 cast(binode, cs->condpart)->op == Block) {
3354 do_indent(indent, "while {\n");
3356 do_indent(indent, "while:\n");
3357 print_exec(cs->condpart, indent+1, bracket);
3359 do_indent(indent, "} do {\n");
3361 do_indent(indent, "do:\n");
3362 print_exec(cs->dopart, indent+1, bracket);
3364 do_indent(indent, "}\n");
3366 do_indent(indent, "while ");
3367 print_exec(cs->condpart, 0, bracket);
3372 print_exec(cs->dopart, indent+1, bracket);
3374 do_indent(indent, "}\n");
3379 do_indent(indent, "switch");
3381 do_indent(indent, "if");
3382 if (cs->condpart && cs->condpart->type == Xbinode &&
3383 cast(binode, cs->condpart)->op == Block) {
3388 print_exec(cs->condpart, indent+1, bracket);
3390 do_indent(indent, "}\n");
3392 do_indent(indent, "then:\n");
3393 print_exec(cs->thenpart, indent+1, bracket);
3397 print_exec(cs->condpart, 0, bracket);
3403 print_exec(cs->thenpart, indent+1, bracket);
3405 do_indent(indent, "}\n");
3410 for (cp = cs->casepart; cp; cp = cp->next) {
3411 do_indent(indent, "case ");
3412 print_exec(cp->value, -1, 0);
3417 print_exec(cp->action, indent+1, bracket);
3419 do_indent(indent, "}\n");
3422 do_indent(indent, "else");
3427 print_exec(cs->elsepart, indent+1, bracket);
3429 do_indent(indent, "}\n");
3434 ###### propagate exec cases
3435 case Xcond_statement:
3437 // forpart and dopart must return Tnone
3438 // thenpart must return Tnone if there is a dopart,
3439 // otherwise it is like elsepart.
3441 // be bool if there is no casepart
3442 // match casepart->values if there is a switchpart
3443 // either be bool or match casepart->value if there
3445 // elsepart and casepart->action must match the return type
3446 // expected of this statement.
3447 struct cond_statement *cs = cast(cond_statement, prog);
3448 struct casepart *cp;
3450 t = propagate_types(cs->forpart, c, ok, Tnone, 0);
3451 if (!type_compat(Tnone, t, 0))
3453 t = propagate_types(cs->dopart, c, ok, Tnone, 0);
3454 if (!type_compat(Tnone, t, 0))
3457 t = propagate_types(cs->thenpart, c, ok, Tnone, 0);
3458 if (!type_compat(Tnone, t, 0))
3461 if (cs->casepart == NULL)
3462 propagate_types(cs->condpart, c, ok, Tbool, 0);
3464 /* Condpart must match case values, with bool permitted */
3466 for (cp = cs->casepart;
3467 cp && !t; cp = cp->next)
3468 t = propagate_types(cp->value, c, ok, NULL, 0);
3469 if (!t && cs->condpart)
3470 t = propagate_types(cs->condpart, c, ok, NULL, Rboolok);
3471 // Now we have a type (I hope) push it down
3473 for (cp = cs->casepart; cp; cp = cp->next)
3474 propagate_types(cp->value, c, ok, t, 0);
3475 propagate_types(cs->condpart, c, ok, t, Rboolok);
3478 // (if)then, else, and case parts must return expected type.
3479 if (!cs->dopart && !type)
3480 type = propagate_types(cs->thenpart, c, ok, NULL, rules);
3482 type = propagate_types(cs->elsepart, c, ok, NULL, rules);
3483 for (cp = cs->casepart;
3486 type = propagate_types(cp->action, c, ok, NULL, rules);
3489 propagate_types(cs->thenpart, c, ok, type, rules);
3490 propagate_types(cs->elsepart, c, ok, type, rules);
3491 for (cp = cs->casepart; cp ; cp = cp->next)
3492 propagate_types(cp->action, c, ok, type, rules);
3498 ###### interp exec cases
3499 case Xcond_statement:
3501 struct value v, cnd;
3502 struct casepart *cp;
3503 struct cond_statement *c = cast(cond_statement, e);
3506 interp_exec(c->forpart);
3509 cnd = interp_exec(c->condpart);
3512 if (!(cnd.type == Tnone ||
3513 (cnd.type == Tbool && cnd.bool != 0)))
3515 // cnd is Tnone or Tbool, doesn't need to be freed
3517 interp_exec(c->dopart);
3520 rv = interp_exec(c->thenpart);
3521 if (rv.type != Tnone || !c->dopart)
3525 } while (c->dopart);
3527 for (cp = c->casepart; cp; cp = cp->next) {
3528 v = interp_exec(cp->value);
3529 if (value_cmp(v, cnd) == 0) {
3532 rv = interp_exec(cp->action);
3539 rv = interp_exec(c->elsepart);
3546 ### Top level structure
3548 All the language elements so far can be used in various places. Now
3549 it is time to clarify what those places are.
3551 At the top level of a file there will be a number of declarations.
3552 Many of the things that can be declared haven't been described yet,
3553 such as functions, procedures, imports, named types, and probably
3555 For now there are two sorts of things that can appear at the top
3556 level. They are predefined constants and the main program. While the
3557 syntax will allow the main program to appear multiple times, that will
3558 trigger an error if it is actually attempted.
3560 The various declarations do not return anything. They store the
3561 various declarations in the parse context.
3563 ###### Parser: grammar
3566 Ocean -> DeclarationList
3568 DeclarationList -> Declaration
3569 | DeclarationList Declaration
3571 Declaration -> DeclareConstant
3575 ## top level grammar
3577 ### Finally the whole program.
3579 Somewhat reminiscent of Pascal a (current) Ocean program starts with
3580 the keyword "program" and a list of variable names which are assigned
3581 values from command line arguments. Following this is a `block` which
3582 is the code to execute. Unlike Pascal, constants and other
3583 declarations come *before* the program.
3585 As this is the top level, several things are handled a bit
3587 The whole program is not interpreted by `interp_exec` as that isn't
3588 passed the argument list which the program requires. Similarly type
3589 analysis is a bit more interesting at this level.
3594 ###### top level grammar
3596 DeclareProgram -> Program ${ {
3597 struct parse_context *c = config2context(config);
3599 type_err(c, "Program defined a second time",
3607 Program -> program OpenScope Varlist Block OptNL ${
3610 $0->left = reorder_bilist($<3);
3612 var_block_close(config2context(config), CloseSequential);
3613 if (config2context(config)->scope_stack) abort();
3616 tok_err(config2context(config),
3617 "error: unhandled parse error", &$1);
3620 Varlist -> Varlist ArgDecl ${
3629 ArgDecl -> IDENTIFIER ${ {
3630 struct variable *v = var_decl(config2context(config), $1.txt);
3637 ###### print binode cases
3639 do_indent(indent, "program");
3640 for (b2 = cast(binode, b->left); b2; b2 = cast(binode, b2->right)) {
3642 print_exec(b2->left, 0, 0);
3648 print_exec(b->right, indent+1, bracket);
3650 do_indent(indent, "}\n");
3653 ###### propagate binode cases
3654 case Program: abort(); // NOTEST
3656 ###### core functions
3658 static int analyse_prog(struct exec *prog, struct parse_context *c)
3660 struct binode *b = cast(binode, prog);
3667 propagate_types(b->right, c, &ok, Tnone, 0);
3672 for (b = cast(binode, b->left); b; b = cast(binode, b->right)) {
3673 struct var *v = cast(var, b->left);
3674 if (!v->var->val.type) {
3675 v->var->where_set = b;
3676 v->var->val = val_prepare(Tstr);
3679 b = cast(binode, prog);
3682 propagate_types(b->right, c, &ok, Tnone, 0);
3687 /* Make sure everything is still consistent */
3688 propagate_types(b->right, c, &ok, Tnone, 0);
3692 static void interp_prog(struct exec *prog, char **argv)
3694 struct binode *p = cast(binode, prog);
3700 al = cast(binode, p->left);
3702 struct var *v = cast(var, al->left);
3703 struct value *vl = &v->var->val;
3705 if (argv[0] == NULL) {
3706 printf("Not enough args\n");
3709 al = cast(binode, al->right);
3711 *vl = parse_value(vl->type, argv[0]);
3712 if (vl->type == NULL)
3716 v = interp_exec(p->right);
3720 ###### interp binode cases
3721 case Program: abort(); // NOTEST
3723 ## And now to test it out.
3725 Having a language requires having a "hello world" program. I'll
3726 provide a little more than that: a program that prints "Hello world"
3727 finds the GCD of two numbers, prints the first few elements of
3728 Fibonacci, and performs a binary search for a number.
3730 ###### File: oceani.mk
3733 @echo "===== TEST ====="
3734 ./oceani --section "test: hello" oceani.mdc 55 33
3739 print "Hello World, what lovely oceans you have!"
3740 /* When a variable is defined in both branches of an 'if',
3741 * and used afterwards, the variables are merged.
3747 print "Is", A, "bigger than", B,"? ", bigger
3748 /* If a variable is not used after the 'if', no
3749 * merge happens, so types can be different
3752 double:string = "yes"
3753 print A, "is more than twice", B, "?", double
3756 print "double", B, "is", double
3761 if a > 0 and then b > 0:
3767 print "GCD of", A, "and", B,"is", a
3769 print a, "is not positive, cannot calculate GCD"
3771 print b, "is not positive, cannot calculate GCD"
3776 print "Fibonacci:", f1,f2,
3777 then togo = togo - 1
3785 /* Binary search... */
3790 mid := (lo + hi) / 2
3802 print "Yay, I found", target
3804 print "Closest I found was", mid
3809 for i:=1; then i = i + 1; while i < size:
3810 n := list[i-1] * list[i-1]
3811 list[i] = (n / 100) % 10000
3813 print "Before sort:"
3814 for i:=0; then i = i + 1; while i < size:
3815 print "list[",i,"]=",list[i]
3817 for i := 1; then i=i+1; while i < size:
3818 for j:=i-1; then j=j-1; while j >= 0:
3819 if list[j] > list[j+1]:
3824 for i:=0; then i = i + 1; while i < size:
3825 print "list[",i,"]=",list[i]