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, \
126 ###### Parser: reduce
127 struct parse_context *c = config2context(config);
135 #include <sys/mman.h>
154 static char Usage[] =
155 "Usage: oceani --trace --print --noexec --brackets --section=SectionName prog.ocn\n";
156 static const struct option long_options[] = {
157 {"trace", 0, NULL, 't'},
158 {"print", 0, NULL, 'p'},
159 {"noexec", 0, NULL, 'n'},
160 {"brackets", 0, NULL, 'b'},
161 {"section", 1, NULL, 's'},
164 const char *options = "tpnbs";
165 int main(int argc, char *argv[])
170 struct section *s, *ss;
171 char *section = NULL;
172 struct parse_context context = {
174 .ignored = (1 << TK_mark),
175 .number_chars = ".,_+- ",
180 int doprint=0, dotrace=0, doexec=1, brackets=0;
182 while ((opt = getopt_long(argc, argv, options, long_options, NULL))
185 case 't': dotrace=1; break;
186 case 'p': doprint=1; break;
187 case 'n': doexec=0; break;
188 case 'b': brackets=1; break;
189 case 's': section = optarg; break;
190 default: fprintf(stderr, Usage);
194 if (optind >= argc) {
195 fprintf(stderr, "oceani: no input file given\n");
198 fd = open(argv[optind], O_RDONLY);
200 fprintf(stderr, "oceani: cannot open %s\n", argv[optind]);
203 context.file_name = argv[optind];
204 len = lseek(fd, 0, 2);
205 file = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
206 s = code_extract(file, file+len, NULL);
208 fprintf(stderr, "oceani: could not find any code in %s\n",
213 ## context initialization
216 for (ss = s; ss; ss = ss->next) {
217 struct text sec = ss->section;
218 if (sec.len == strlen(section) &&
219 strncmp(sec.txt, section, sec.len) == 0)
223 fprintf(stderr, "oceani: cannot find section %s\n",
229 parse_oceani(ss->code, &context.config, dotrace ? stderr : NULL);
232 fprintf(stderr, "oceani: no program found.\n");
233 context.parse_error = 1;
235 if (context.prog && doprint) {
238 print_exec(context.prog, 0, brackets);
240 if (context.prog && doexec && !context.parse_error) {
241 if (!analyse_prog(context.prog, &context)) {
242 fprintf(stderr, "oceani: type error in program - not running.\n");
245 interp_prog(context.prog, argv+optind+1);
247 free_exec(context.prog);
250 struct section *t = s->next;
256 ## free context types
257 exit(context.parse_error ? 1 : 0);
262 The four requirements of parse, analyse, print, interpret apply to
263 each language element individually so that is how most of the code
266 Three of the four are fairly self explanatory. The one that requires
267 a little explanation is the analysis step.
269 The current language design does not require the types of variables to
270 be declared, but they must still have a single type. Different
271 operations impose different requirements on the variables, for example
272 addition requires both arguments to be numeric, and assignment
273 requires the variable on the left to have the same type as the
274 expression on the right.
276 Analysis involves propagating these type requirements around and
277 consequently setting the type of each variable. If any requirements
278 are violated (e.g. a string is compared with a number) or if a
279 variable needs to have two different types, then an error is raised
280 and the program will not run.
282 If the same variable is declared in both branchs of an 'if/else', or
283 in all cases of a 'switch' then the multiple instances may be merged
284 into just one variable if the variable is referenced after the
285 conditional statement. When this happens, the types must naturally be
286 consistent across all the branches. When the variable is not used
287 outside the if, the variables in the different branches are distinct
288 and can be of different types.
290 Undeclared names may only appear in "use" statements and "case" expressions.
291 These names are given a type of "label" and a unique value.
292 This allows them to fill the role of a name in an enumerated type, which
293 is useful for testing the `switch` statement.
295 As we will see, the condition part of a `while` statement can return
296 either a Boolean or some other type. This requires that the expected
297 type that gets passed around comprises a type and a flag to indicate
298 that `Tbool` is also permitted.
300 As there are, as yet, no distinct types that are compatible, there
301 isn't much subtlety in the analysis. When we have distinct number
302 types, this will become more interesting.
306 When analysis discovers an inconsistency it needs to report an error;
307 just refusing to run the code ensures that the error doesn't cascade,
308 but by itself it isn't very useful. A clear understanding of the sort
309 of error message that are useful will help guide the process of
312 At a simplistic level, the only sort of error that type analysis can
313 report is that the type of some construct doesn't match a contextual
314 requirement. For example, in `4 + "hello"` the addition provides a
315 contextual requirement for numbers, but `"hello"` is not a number. In
316 this particular example no further information is needed as the types
317 are obvious from local information. When a variable is involved that
318 isn't the case. It may be helpful to explain why the variable has a
319 particular type, by indicating the location where the type was set,
320 whether by declaration or usage.
322 Using a recursive-descent analysis we can easily detect a problem at
323 multiple locations. In "`hello:= "there"; 4 + hello`" the addition
324 will detect that one argument is not a number and the usage of `hello`
325 will detect that a number was wanted, but not provided. In this
326 (early) version of the language, we will generate error reports at
327 multiple locations, so the use of `hello` will report an error and
328 explain were the value was set, and the addition will report an error
329 and say why numbers are needed. To be able to report locations for
330 errors, each language element will need to record a file location
331 (line and column) and each variable will need to record the language
332 element where its type was set. For now we will assume that each line
333 of an error message indicates one location in the file, and up to 2
334 types. So we provide a `printf`-like function which takes a format, a
335 location (a `struct exec` which has not yet been introduced), and 2
336 types. "`%1`" reports the first type, "`%2`" reports the second. We
337 will need a function to print the location, once we know how that is
338 stored. e As will be explained later, there are sometimes extra rules for
339 type matching and they might affect error messages, we need to pass those
342 As well as type errors, we sometimes need to report problems with
343 tokens, which might be unexpected or might name a type that has not
344 been defined. For these we have `tok_err()` which reports an error
345 with a given token. Each of the error functions sets the flag in the
346 context so indicate that parsing failed.
350 static void fput_loc(struct exec *loc, FILE *f);
352 ###### core functions
354 static void type_err(struct parse_context *c,
355 char *fmt, struct exec *loc,
356 struct type *t1, int rules, struct type *t2)
358 fprintf(stderr, "%s:", c->file_name);
359 fput_loc(loc, stderr);
360 for (; *fmt ; fmt++) {
367 case '%': fputc(*fmt, stderr); break; // NOTEST
368 default: fputc('?', stderr); break; // NOTEST
370 type_print(t1, stderr);
373 type_print(t2, stderr);
382 static void tok_err(struct parse_context *c, char *fmt, struct token *t)
384 fprintf(stderr, "%s:%d:%d: %s: %.*s\n", c->file_name, t->line, t->col, fmt,
385 t->txt.len, t->txt.txt);
389 ## Entities: declared and predeclared.
391 There are various "things" that the language and/or the interpreter
392 needs to know about to parse and execute a program. These include
393 types, variables, values, and executable code. These are all lumped
394 together under the term "entities" (calling them "objects" would be
395 confusing) and introduced here. The following section will present the
396 different specific code elements which comprise or manipulate these
401 Values come in a wide range of types, with more likely to be added.
402 Each type needs to be able to print its own values (for convenience at
403 least) as well as to compare two values, at least for equality and
404 possibly for order. For now, values might need to be duplicated and
405 freed, though eventually such manipulations will be better integrated
408 Rather than requiring every numeric type to support all numeric
409 operations (add, multiple, etc), we allow types to be able to present
410 as one of a few standard types: integer, float, and fraction. The
411 existence of these conversion functions eventually enable types to
412 determine if they are compatible with other types, though such types
413 have not yet been implemented.
415 Named type are stored in a simple linked list. Objects of each type are
416 "values" which are often passed around by value.
423 ## value union fields
431 void (*init)(struct type *type, struct value *val);
432 void (*print)(struct type *type, struct value *val);
433 void (*print_type)(struct type *type, FILE *f);
434 int (*cmp_order)(struct type *t1, struct type *t2,
435 struct value *v1, struct value *v2);
436 int (*cmp_eq)(struct type *t1, struct type *t2,
437 struct value *v1, struct value *v2);
438 void (*dup)(struct type *type, struct value *vold, struct value *vnew);
439 void (*free)(struct type *type, struct value *val);
440 void (*free_type)(struct type *t);
441 long long (*to_int)(struct value *v);
442 double (*to_float)(struct value *v);
443 int (*to_mpq)(mpq_t *q, struct value *v);
452 struct type *typelist;
456 static struct type *find_type(struct parse_context *c, struct text s)
458 struct type *l = c->typelist;
461 text_cmp(l->name, s) != 0)
466 static struct type *add_type(struct parse_context *c, struct text s,
471 n = calloc(1, sizeof(*n));
474 n->next = c->typelist;
479 static void free_type(struct type *t)
481 /* The type is always a reference to something in the
482 * context, so we don't need to free anything.
486 static void free_value(struct type *type, struct value *v)
492 static void type_print(struct type *type, FILE *f)
495 fputs("*unknown*type*", f);
496 else if (type->name.len)
497 fprintf(f, "%.*s", type->name.len, type->name.txt);
498 else if (type->print_type)
499 type->print_type(type, f);
501 fputs("*invalid*type*", f); // NOTEST
504 static void val_init(struct type *type, struct value *val)
506 if (type && type->init)
507 type->init(type, val);
510 static void dup_value(struct type *type,
511 struct value *vold, struct value *vnew)
513 if (type && type->dup)
514 type->dup(type, vold, vnew);
517 static int value_cmp(struct type *tl, struct type *tr,
518 struct value *left, struct value *right)
520 if (tl && tl->cmp_order)
521 return tl->cmp_order(tl, tr, left, right);
522 if (tl && tl->cmp_eq)
523 return tl->cmp_eq(tl, tr, left, right);
527 static void print_value(struct type *type, struct value *v)
529 if (type && type->print)
530 type->print(type, v);
532 printf("*Unknown*"); // NOTEST
535 static struct value *val_alloc(struct type *t, struct value *init)
541 ret = calloc(1, t->size);
543 memcpy(ret, init, t->size);
551 static void free_value(struct type *type, struct value *v);
552 static int type_compat(struct type *require, struct type *have, int rules);
553 static void type_print(struct type *type, FILE *f);
554 static void val_init(struct type *type, struct value *v);
555 static void dup_value(struct type *type,
556 struct value *vold, struct value *vnew);
557 static int value_cmp(struct type *tl, struct type *tr,
558 struct value *left, struct value *right);
559 static void print_value(struct type *type, struct value *v);
561 ###### free context types
563 while (context.typelist) {
564 struct type *t = context.typelist;
566 context.typelist = t->next;
574 Values of the base types can be numbers, which we represent as
575 multi-precision fractions, strings, Booleans and labels. When
576 analysing the program we also need to allow for places where no value
577 is meaningful (type `Tnone`) and where we don't know what type to
578 expect yet (type is `NULL`).
580 Values are never shared, they are always copied when used, and freed
581 when no longer needed.
583 When propagating type information around the program, we need to
584 determine if two types are compatible, where type `NULL` is compatible
585 with anything. There are two special cases with type compatibility,
586 both related to the Conditional Statement which will be described
587 later. In some cases a Boolean can be accepted as well as some other
588 primary type, and in others any type is acceptable except a label (`Vlabel`).
589 A separate function encoding these cases will simplify some code later.
593 int (*compat)(struct type *this, struct type *other);
597 static int type_compat(struct type *require, struct type *have, int rules)
599 if ((rules & Rboolok) && have == Tbool)
601 if ((rules & Rnolabel) && have == Tlabel)
603 if (!require || !have)
607 return require->compat(require, have);
609 return require == have;
614 #include "parse_string.h"
615 #include "parse_number.h"
618 myLDLIBS := libnumber.o libstring.o -lgmp
619 LDLIBS := $(filter-out $(myLDLIBS),$(LDLIBS)) $(myLDLIBS)
621 ###### type union fields
622 enum vtype {Vnone, Vstr, Vnum, Vbool, Vlabel} vtype;
624 ###### value union fields
631 static void _free_value(struct type *type, struct value *v)
635 switch (type->vtype) {
637 case Vstr: free(v->str.txt); break;
638 case Vnum: mpq_clear(v->num); break;
644 ###### value functions
646 static void _val_init(struct type *type, struct value *val)
648 switch(type->vtype) {
649 case Vnone: // NOTEST
652 mpq_init(val->num); break;
654 val->str.txt = malloc(1);
660 case Vlabel: // NOTEST
661 val->label = NULL; // NOTEST
666 static void _dup_value(struct type *type,
667 struct value *vold, struct value *vnew)
669 switch (type->vtype) {
670 case Vnone: // NOTEST
673 vnew->label = vold->label;
676 vnew->bool = vold->bool;
680 mpq_set(vnew->num, vold->num);
683 vnew->str.len = vold->str.len;
684 vnew->str.txt = malloc(vnew->str.len);
685 memcpy(vnew->str.txt, vold->str.txt, vnew->str.len);
690 static int _value_cmp(struct type *tl, struct type *tr,
691 struct value *left, struct value *right)
695 return tl - tr; // NOTEST
697 case Vlabel: cmp = left->label == right->label ? 0 : 1; break;
698 case Vnum: cmp = mpq_cmp(left->num, right->num); break;
699 case Vstr: cmp = text_cmp(left->str, right->str); break;
700 case Vbool: cmp = left->bool - right->bool; break;
701 case Vnone: cmp = 0; // NOTEST
706 static void _print_value(struct type *type, struct value *v)
708 switch (type->vtype) {
709 case Vnone: // NOTEST
710 printf("*no-value*"); break; // NOTEST
711 case Vlabel: // NOTEST
712 printf("*label-%p*", v->label); break; // NOTEST
714 printf("%.*s", v->str.len, v->str.txt); break;
716 printf("%s", v->bool ? "True":"False"); break;
721 mpf_set_q(fl, v->num);
722 gmp_printf("%Fg", fl);
729 static void _free_value(struct type *type, struct value *v);
731 static struct type base_prototype = {
733 .print = _print_value,
734 .cmp_order = _value_cmp,
735 .cmp_eq = _value_cmp,
740 static struct type *Tbool, *Tstr, *Tnum, *Tnone, *Tlabel;
743 static struct type *add_base_type(struct parse_context *c, char *n,
744 enum vtype vt, int size)
746 struct text txt = { n, strlen(n) };
749 t = add_type(c, txt, &base_prototype);
752 t->align = size > sizeof(void*) ? sizeof(void*) : size;
753 if (t->size & (t->align - 1))
754 t->size = (t->size | (t->align - 1)) + 1;
758 ###### context initialization
760 Tbool = add_base_type(&context, "Boolean", Vbool, sizeof(char));
761 Tstr = add_base_type(&context, "string", Vstr, sizeof(struct text));
762 Tnum = add_base_type(&context, "number", Vnum, sizeof(mpq_t));
763 Tnone = add_base_type(&context, "none", Vnone, 0);
764 Tlabel = add_base_type(&context, "label", Vlabel, sizeof(void*));
768 Variables are scoped named values. We store the names in a linked list
769 of "bindings" sorted in lexical order, and use sequential search and
776 struct binding *next; // in lexical order
780 This linked list is stored in the parse context so that "reduce"
781 functions can find or add variables, and so the analysis phase can
782 ensure that every variable gets a type.
786 struct binding *varlist; // In lexical order
790 static struct binding *find_binding(struct parse_context *c, struct text s)
792 struct binding **l = &c->varlist;
797 (cmp = text_cmp((*l)->name, s)) < 0)
801 n = calloc(1, sizeof(*n));
808 Each name can be linked to multiple variables defined in different
809 scopes. Each scope starts where the name is declared and continues
810 until the end of the containing code block. Scopes of a given name
811 cannot nest, so a declaration while a name is in-scope is an error.
813 ###### binding fields
814 struct variable *var;
818 struct variable *previous;
821 struct binding *name;
822 struct exec *where_decl;// where name was declared
823 struct exec *where_set; // where type was set
827 While the naming seems strange, we include local constants in the
828 definition of variables. A name declared `var := value` can
829 subsequently be changed, but a name declared `var ::= value` cannot -
832 ###### variable fields
835 Scopes in parallel branches can be partially merged. More
836 specifically, if a given name is declared in both branches of an
837 if/else then its scope is a candidate for merging. Similarly if
838 every branch of an exhaustive switch (e.g. has an "else" clause)
839 declares a given name, then the scopes from the branches are
840 candidates for merging.
842 Note that names declared inside a loop (which is only parallel to
843 itself) are never visible after the loop. Similarly names defined in
844 scopes which are not parallel, such as those started by `for` and
845 `switch`, are never visible after the scope. Only variables defined in
846 both `then` and `else` (including the implicit then after an `if`, and
847 excluding `then` used with `for`) and in all `case`s and `else` of a
848 `switch` or `while` can be visible beyond the `if`/`switch`/`while`.
850 Labels, which are a bit like variables, follow different rules.
851 Labels are not explicitly declared, but if an undeclared name appears
852 in a context where a label is legal, that effectively declares the
853 name as a label. The declaration remains in force (or in scope) at
854 least to the end of the immediately containing block and conditionally
855 in any larger containing block which does not declare the name in some
856 other way. Importantly, the conditional scope extension happens even
857 if the label is only used in one parallel branch of a conditional --
858 when used in one branch it is treated as having been declared in all
861 Merge candidates are tentatively visible beyond the end of the
862 branching statement which creates them. If the name is used, the
863 merge is affirmed and they become a single variable visible at the
864 outer layer. If not - if it is redeclared first - the merge lapses.
866 To track scopes we have an extra stack, implemented as a linked list,
867 which roughly parallels the parse stack and which is used exclusively
868 for scoping. When a new scope is opened, a new frame is pushed and
869 the child-count of the parent frame is incremented. This child-count
870 is used to distinguish between the first of a set of parallel scopes,
871 in which declared variables must not be in scope, and subsequent
872 branches, whether they may already be conditionally scoped.
874 To push a new frame *before* any code in the frame is parsed, we need a
875 grammar reduction. This is most easily achieved with a grammar
876 element which derives the empty string, and creates the new scope when
877 it is recognised. This can be placed, for example, between a keyword
878 like "if" and the code following it.
882 struct scope *parent;
888 struct scope *scope_stack;
891 static void scope_pop(struct parse_context *c)
893 struct scope *s = c->scope_stack;
895 c->scope_stack = s->parent;
900 static void scope_push(struct parse_context *c)
902 struct scope *s = calloc(1, sizeof(*s));
904 c->scope_stack->child_count += 1;
905 s->parent = c->scope_stack;
913 OpenScope -> ${ scope_push(c); }$
914 ClosePara -> ${ var_block_close(c, CloseParallel); }$
916 Each variable records a scope depth and is in one of four states:
918 - "in scope". This is the case between the declaration of the
919 variable and the end of the containing block, and also between
920 the usage with affirms a merge and the end of that block.
922 The scope depth is not greater than the current parse context scope
923 nest depth. When the block of that depth closes, the state will
924 change. To achieve this, all "in scope" variables are linked
925 together as a stack in nesting order.
927 - "pending". The "in scope" block has closed, but other parallel
928 scopes are still being processed. So far, every parallel block at
929 the same level that has closed has declared the name.
931 The scope depth is the depth of the last parallel block that
932 enclosed the declaration, and that has closed.
934 - "conditionally in scope". The "in scope" block and all parallel
935 scopes have closed, and no further mention of the name has been
936 seen. This state includes a secondary nest depth which records the
937 outermost scope seen since the variable became conditionally in
938 scope. If a use of the name is found, the variable becomes "in
939 scope" and that secondary depth becomes the recorded scope depth.
940 If the name is declared as a new variable, the old variable becomes
941 "out of scope" and the recorded scope depth stays unchanged.
943 - "out of scope". The variable is neither in scope nor conditionally
944 in scope. It is permanently out of scope now and can be removed from
945 the "in scope" stack.
947 ###### variable fields
948 int depth, min_depth;
949 enum { OutScope, PendingScope, CondScope, InScope } scope;
950 struct variable *in_scope;
954 struct variable *in_scope;
956 All variables with the same name are linked together using the
957 'previous' link. Those variable that have been affirmatively merged all
958 have a 'merged' pointer that points to one primary variable - the most
959 recently declared instance. When merging variables, we need to also
960 adjust the 'merged' pointer on any other variables that had previously
961 been merged with the one that will no longer be primary.
963 A variable that is no longer the most recent instance of a name may
964 still have "pending" scope, if it might still be merged with most
965 recent instance. These variables don't really belong in the
966 "in_scope" list, but are not immediately removed when a new instance
967 is found. Instead, they are detected and ignored when considering the
968 list of in_scope names.
970 ###### variable fields
971 struct variable *merged;
975 static void variable_merge(struct variable *primary, struct variable *secondary)
981 primary = primary->merged;
983 for (v = primary->previous; v; v=v->previous)
984 if (v == secondary || v == secondary->merged ||
985 v->merged == secondary ||
986 (v->merged && v->merged == secondary->merged)) {
992 ###### free context vars
994 while (context.varlist) {
995 struct binding *b = context.varlist;
996 struct variable *v = b->var;
997 context.varlist = b->next;
1000 struct variable *t = v;
1003 free_value(t->type, t->val);
1006 // This is a global constant
1007 free_exec(t->where_decl);
1012 #### Manipulating Bindings
1014 When a name is conditionally visible, a new declaration discards the
1015 old binding - the condition lapses. Conversely a usage of the name
1016 affirms the visibility and extends it to the end of the containing
1017 block - i.e. the block that contains both the original declaration and
1018 the latest usage. This is determined from `min_depth`. When a
1019 conditionally visible variable gets affirmed like this, it is also
1020 merged with other conditionally visible variables with the same name.
1022 When we parse a variable declaration we either report an error if the
1023 name is currently bound, or create a new variable at the current nest
1024 depth if the name is unbound or bound to a conditionally scoped or
1025 pending-scope variable. If the previous variable was conditionally
1026 scoped, it and its homonyms becomes out-of-scope.
1028 When we parse a variable reference (including non-declarative assignment
1029 "foo = bar") we report an error if the name is not bound or is bound to
1030 a pending-scope variable; update the scope if the name is bound to a
1031 conditionally scoped variable; or just proceed normally if the named
1032 variable is in scope.
1034 When we exit a scope, any variables bound at this level are either
1035 marked out of scope or pending-scoped, depending on whether the scope
1036 was sequential or parallel. Here a "parallel" scope means the "then"
1037 or "else" part of a conditional, or any "case" or "else" branch of a
1038 switch. Other scopes are "sequential".
1040 When exiting a parallel scope we check if there are any variables that
1041 were previously pending and are still visible. If there are, then
1042 there weren't redeclared in the most recent scope, so they cannot be
1043 merged and must become out-of-scope. If it is not the first of
1044 parallel scopes (based on `child_count`), we check that there was a
1045 previous binding that is still pending-scope. If there isn't, the new
1046 variable must now be out-of-scope.
1048 When exiting a sequential scope that immediately enclosed parallel
1049 scopes, we need to resolve any pending-scope variables. If there was
1050 no `else` clause, and we cannot determine that the `switch` was exhaustive,
1051 we need to mark all pending-scope variable as out-of-scope. Otherwise
1052 all pending-scope variables become conditionally scoped.
1055 enum closetype { CloseSequential, CloseParallel, CloseElse };
1057 ###### ast functions
1059 static struct variable *var_decl(struct parse_context *c, struct text s)
1061 struct binding *b = find_binding(c, s);
1062 struct variable *v = b->var;
1064 switch (v ? v->scope : OutScope) {
1066 /* Caller will report the error */
1070 v && v->scope == CondScope;
1072 v->scope = OutScope;
1076 v = calloc(1, sizeof(*v));
1077 v->previous = b->var;
1080 v->min_depth = v->depth = c->scope_depth;
1082 v->in_scope = c->in_scope;
1088 static struct variable *var_ref(struct parse_context *c, struct text s)
1090 struct binding *b = find_binding(c, s);
1091 struct variable *v = b->var;
1092 struct variable *v2;
1094 switch (v ? v->scope : OutScope) {
1097 /* Caller will report the error */
1100 /* All CondScope variables of this name need to be merged
1101 * and become InScope
1103 v->depth = v->min_depth;
1105 for (v2 = v->previous;
1106 v2 && v2->scope == CondScope;
1108 variable_merge(v, v2);
1116 static void var_block_close(struct parse_context *c, enum closetype ct)
1118 /* Close off all variables that are in_scope */
1119 struct variable *v, **vp, *v2;
1122 for (vp = &c->in_scope;
1123 v = *vp, v && v->depth > c->scope_depth && v->min_depth > c->scope_depth;
1125 if (v->name->var == v) switch (ct) {
1127 case CloseParallel: /* handle PendingScope */
1131 if (c->scope_stack->child_count == 1)
1132 v->scope = PendingScope;
1133 else if (v->previous &&
1134 v->previous->scope == PendingScope)
1135 v->scope = PendingScope;
1136 else if (v->type == Tlabel)
1137 v->scope = PendingScope;
1138 else if (v->name->var == v)
1139 v->scope = OutScope;
1140 if (ct == CloseElse) {
1141 /* All Pending variables with this name
1142 * are now Conditional */
1144 v2 && v2->scope == PendingScope;
1146 v2->scope = CondScope;
1151 v2 && v2->scope == PendingScope;
1153 if (v2->type != Tlabel)
1154 v2->scope = OutScope;
1156 case OutScope: break;
1159 case CloseSequential:
1160 if (v->type == Tlabel)
1161 v->scope = PendingScope;
1164 v->scope = OutScope;
1167 /* There was no 'else', so we can only become
1168 * conditional if we know the cases were exhaustive,
1169 * and that doesn't mean anything yet.
1170 * So only labels become conditional..
1173 v2 && v2->scope == PendingScope;
1175 if (v2->type == Tlabel) {
1176 v2->scope = CondScope;
1177 v2->min_depth = c->scope_depth;
1179 v2->scope = OutScope;
1182 case OutScope: break;
1186 if (v->scope == OutScope || v->name->var != v)
1195 Executables can be lots of different things. In many cases an
1196 executable is just an operation combined with one or two other
1197 executables. This allows for expressions and lists etc. Other times an
1198 executable is something quite specific like a constant or variable name.
1199 So we define a `struct exec` to be a general executable with a type, and
1200 a `struct binode` which is a subclass of `exec`, forms a node in a
1201 binary tree, and holds an operation. There will be other subclasses,
1202 and to access these we need to be able to `cast` the `exec` into the
1203 various other types. The first field in any `struct exec` is the type
1204 from the `exec_types` enum.
1207 #define cast(structname, pointer) ({ \
1208 const typeof( ((struct structname *)0)->type) *__mptr = &(pointer)->type; \
1209 if (__mptr && *__mptr != X##structname) abort(); \
1210 (struct structname *)( (char *)__mptr);})
1212 #define new(structname) ({ \
1213 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1214 __ptr->type = X##structname; \
1215 __ptr->line = -1; __ptr->column = -1; \
1218 #define new_pos(structname, token) ({ \
1219 struct structname *__ptr = ((struct structname *)calloc(1,sizeof(struct structname))); \
1220 __ptr->type = X##structname; \
1221 __ptr->line = token.line; __ptr->column = token.col; \
1230 enum exec_types type;
1238 struct exec *left, *right;
1241 ###### ast functions
1243 static int __fput_loc(struct exec *loc, FILE *f)
1247 if (loc->line >= 0) {
1248 fprintf(f, "%d:%d: ", loc->line, loc->column);
1251 if (loc->type == Xbinode)
1252 return __fput_loc(cast(binode,loc)->left, f) ||
1253 __fput_loc(cast(binode,loc)->right, f);
1256 static void fput_loc(struct exec *loc, FILE *f)
1258 if (!__fput_loc(loc, f))
1259 fprintf(f, "??:??: "); // NOTEST
1262 Each different type of `exec` node needs a number of functions defined,
1263 a bit like methods. We must be able to free it, print it, analyse it
1264 and execute it. Once we have specific `exec` types we will need to
1265 parse them too. Let's take this a bit more slowly.
1269 The parser generator requires a `free_foo` function for each struct
1270 that stores attributes and they will often be `exec`s and subtypes
1271 there-of. So we need `free_exec` which can handle all the subtypes,
1272 and we need `free_binode`.
1274 ###### ast functions
1276 static void free_binode(struct binode *b)
1281 free_exec(b->right);
1285 ###### core functions
1286 static void free_exec(struct exec *e)
1295 ###### forward decls
1297 static void free_exec(struct exec *e);
1299 ###### free exec cases
1300 case Xbinode: free_binode(cast(binode, e)); break;
1304 Printing an `exec` requires that we know the current indent level for
1305 printing line-oriented components. As will become clear later, we
1306 also want to know what sort of bracketing to use.
1308 ###### ast functions
1310 static void do_indent(int i, char *str)
1317 ###### core functions
1318 static void print_binode(struct binode *b, int indent, int bracket)
1322 ## print binode cases
1326 static void print_exec(struct exec *e, int indent, int bracket)
1332 print_binode(cast(binode, e), indent, bracket); break;
1337 ###### forward decls
1339 static void print_exec(struct exec *e, int indent, int bracket);
1343 As discussed, analysis involves propagating type requirements around the
1344 program and looking for errors.
1346 So `propagate_types` is passed an expected type (being a `struct type`
1347 pointer together with some `val_rules` flags) that the `exec` is
1348 expected to return, and returns the type that it does return, either
1349 of which can be `NULL` signifying "unknown". An `ok` flag is passed
1350 by reference. It is set to `0` when an error is found, and `2` when
1351 any change is made. If it remains unchanged at `1`, then no more
1352 propagation is needed.
1356 enum val_rules {Rnolabel = 1<<0, Rboolok = 1<<1, Rnoconstant = 2<<1};
1360 if (rules & Rnolabel)
1361 fputs(" (labels not permitted)", stderr);
1364 ###### core functions
1366 static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1367 struct type *type, int rules);
1368 static struct type *__propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1369 struct type *type, int rules)
1376 switch (prog->type) {
1379 struct binode *b = cast(binode, prog);
1381 ## propagate binode cases
1385 ## propagate exec cases
1390 static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
1391 struct type *type, int rules)
1393 struct type *ret = __propagate_types(prog, c, ok, type, rules);
1402 Interpreting an `exec` doesn't require anything but the `exec`. State
1403 is stored in variables and each variable will be directly linked from
1404 within the `exec` tree. The exception to this is the whole `program`
1405 which needs to look at command line arguments. The `program` will be
1406 interpreted separately.
1408 Each `exec` can return a value combined with a type in `struct lrval`.
1409 The type may be `Tnone` but must be non-NULL. Some `exec`s will return
1410 the location of a value, which can be updated, in `lval`. Others will
1411 set `lval` to NULL indicating that there is a value of appropriate type
1415 ###### core functions
1419 struct value rval, *lval;
1422 static struct lrval _interp_exec(struct exec *e);
1424 static struct value interp_exec(struct exec *e, struct type **typeret)
1426 struct lrval ret = _interp_exec(e);
1428 if (!ret.type) abort();
1430 *typeret = ret.type;
1432 dup_value(ret.type, ret.lval, &ret.rval);
1436 static struct value *linterp_exec(struct exec *e, struct type **typeret)
1438 struct lrval ret = _interp_exec(e);
1441 *typeret = ret.type;
1445 static struct lrval _interp_exec(struct exec *e)
1448 struct value rv = {}, *lrv = NULL;
1449 struct type *rvtype;
1451 rvtype = ret.type = Tnone;
1461 struct binode *b = cast(binode, e);
1462 struct value left, right, *lleft;
1463 struct type *ltype, *rtype;
1464 ltype = rtype = Tnone;
1466 ## interp binode cases
1468 free_value(ltype, &left);
1469 free_value(rtype, &right);
1472 ## interp exec cases
1482 Now that we have the shape of the interpreter in place we can add some
1483 complex types and connected them in to the data structures and the
1484 different phases of parse, analyse, print, interpret.
1486 Thus far we have arrays and structs.
1488 Some complex types need do not exist in a name table, so they are kept
1489 on a linked list in the context (`anon_typelist`). This allows them to
1490 be freed when parsing is complete.
1494 Arrays can be declared by giving a size and a type, as `[size]type' so
1495 `freq:[26]number` declares `freq` to be an array of 26 numbers. The
1496 size can be either a literal number, or a named constant. Some day an
1497 arbitrary expression will be supported.
1499 Arrays cannot be assigned. When pointers are introduced we will also
1500 introduce array slices which can refer to part or all of an array -
1501 the assignment syntax will create a slice. For now, an array can only
1502 ever be referenced by the name it is declared with. It is likely that
1503 a "`copy`" primitive will eventually be define which can be used to
1504 make a copy of an array with controllable recursive depth.
1506 ###### type union fields
1510 struct variable *vsize;
1511 struct type *member;
1514 ###### value union fields
1517 ###### value functions
1519 static void array_init(struct type *type, struct value *val)
1523 if (type->array.vsize) {
1526 mpz_tdiv_q(q, mpq_numref(type->array.vsize->val->num),
1527 mpq_denref(type->array.vsize->val->num));
1528 type->array.size = mpz_get_si(q);
1531 type->size = type->array.size * type->array.member->size;
1532 type->align = type->array.member->align;
1536 for (i = 0; i < type->array.size; i++) {
1538 v = (void*)val->ptr + i * type->array.member->size;
1539 val_init(type->array.member, v);
1543 static void array_free(struct type *type, struct value *val)
1547 for (i = 0; i < type->array.size; i++) {
1549 v = (void*)val->ptr + i * type->array.member->size;
1550 free_value(type->array.member, v);
1554 static int array_compat(struct type *require, struct type *have)
1556 if (have->compat != require->compat)
1558 /* Both are arrays, so we can look at details */
1559 if (!type_compat(require->array.member, have->array.member, 0))
1561 if (require->array.vsize == NULL && have->array.vsize == NULL)
1562 return require->array.size == have->array.size;
1564 return require->array.vsize == have->array.vsize;
1567 static void array_print_type(struct type *type, FILE *f)
1570 if (type->array.vsize) {
1571 struct binding *b = type->array.vsize->name;
1572 fprintf(f, "%.*s]", b->name.len, b->name.txt);
1574 fprintf(f, "%d]", type->array.size);
1575 type_print(type->array.member, f);
1578 static struct type array_prototype = {
1580 .print_type = array_print_type,
1581 .compat = array_compat,
1587 | [ NUMBER ] Type ${
1588 $0 = calloc(1, sizeof(struct type));
1589 *($0) = array_prototype;
1590 $0->array.member = $<4;
1591 $0->array.vsize = NULL;
1595 if (number_parse(num, tail, $2.txt) == 0)
1596 tok_err(c, "error: unrecognised number", &$2);
1598 tok_err(c, "error: unsupported number suffix", &$2);
1600 $0->array.size = mpz_get_ui(mpq_numref(num));
1601 if (mpz_cmp_ui(mpq_denref(num), 1) != 0) {
1602 tok_err(c, "error: array size must be an integer",
1604 } else if (mpz_cmp_ui(mpq_numref(num), 1UL << 30) >= 0)
1605 tok_err(c, "error: array size is too large",
1609 $0->next = c->anon_typelist;
1610 c->anon_typelist = $0;
1614 | [ IDENTIFIER ] Type ${ {
1615 struct variable *v = var_ref(c, $2.txt);
1618 tok_err(c, "error: name undeclared", &$2);
1619 else if (!v->constant)
1620 tok_err(c, "error: array size must be a constant", &$2);
1622 $0 = calloc(1, sizeof(struct type));
1623 *($0) = array_prototype;
1624 $0->array.member = $<4;
1626 $0->array.vsize = v;
1627 $0->next = c->anon_typelist;
1628 c->anon_typelist = $0;
1631 ###### parse context
1633 struct type *anon_typelist;
1635 ###### free context types
1637 while (context.anon_typelist) {
1638 struct type *t = context.anon_typelist;
1640 context.anon_typelist = t->next;
1647 ###### variable grammar
1649 | Variable [ Expression ] ${ {
1650 struct binode *b = new(binode);
1657 ###### print binode cases
1659 print_exec(b->left, -1, bracket);
1661 print_exec(b->right, -1, bracket);
1665 ###### propagate binode cases
1667 /* left must be an array, right must be a number,
1668 * result is the member type of the array
1670 propagate_types(b->right, c, ok, Tnum, 0);
1671 t = propagate_types(b->left, c, ok, NULL, rules & Rnoconstant);
1672 if (!t || t->compat != array_compat) {
1673 type_err(c, "error: %1 cannot be indexed", prog, t, 0, NULL);
1676 if (!type_compat(type, t->array.member, rules)) {
1677 type_err(c, "error: have %1 but need %2", prog,
1678 t->array.member, rules, type);
1680 return t->array.member;
1684 ###### interp binode cases
1689 lleft = linterp_exec(b->left, <ype);
1690 right = interp_exec(b->right, &rtype);
1692 mpz_tdiv_q(q, mpq_numref(right.num), mpq_denref(right.num));
1696 rvtype = ltype->array.member;
1697 if (i >= 0 && i < ltype->array.size)
1698 lrv = (void*)lleft + i * rvtype->size;
1700 val_init(ltype->array.member, &rv);
1707 A `struct` is a data-type that contains one or more other data-types.
1708 It differs from an array in that each member can be of a different
1709 type, and they are accessed by name rather than by number. Thus you
1710 cannot choose an element by calculation, you need to know what you
1713 The language makes no promises about how a given structure will be
1714 stored in memory - it is free to rearrange fields to suit whatever
1715 criteria seems important.
1717 Structs are declared separately from program code - they cannot be
1718 declared in-line in a variable declaration like arrays can. A struct
1719 is given a name and this name is used to identify the type - the name
1720 is not prefixed by the word `struct` as it would be in C.
1722 Structs are only treated as the same if they have the same name.
1723 Simply having the same fields in the same order is not enough. This
1724 might change once we can create structure initializers from a list of
1727 Each component datum is identified much like a variable is declared,
1728 with a name, one or two colons, and a type. The type cannot be omitted
1729 as there is no opportunity to deduce the type from usage. An initial
1730 value can be given following an equals sign, so
1732 ##### Example: a struct type
1738 would declare a type called "complex" which has two number fields,
1739 each initialised to zero.
1741 Struct will need to be declared separately from the code that uses
1742 them, so we will need to be able to print out the declaration of a
1743 struct when reprinting the whole program. So a `print_type_decl` type
1744 function will be needed.
1746 ###### type union fields
1758 ###### type functions
1759 void (*print_type_decl)(struct type *type, FILE *f);
1761 ###### value functions
1763 static void structure_init(struct type *type, struct value *val)
1767 for (i = 0; i < type->structure.nfields; i++) {
1769 v = (void*) val->ptr + type->structure.fields[i].offset;
1770 val_init(type->structure.fields[i].type, v);
1774 static void structure_free(struct type *type, struct value *val)
1778 for (i = 0; i < type->structure.nfields; i++) {
1780 v = (void*)val->ptr + type->structure.fields[i].offset;
1781 free_value(type->structure.fields[i].type, v);
1785 static void structure_free_type(struct type *t)
1788 for (i = 0; i < t->structure.nfields; i++)
1789 if (t->structure.fields[i].init) {
1790 free_value(t->structure.fields[i].type,
1791 t->structure.fields[i].init);
1792 free(t->structure.fields[i].init);
1794 free(t->structure.fields);
1797 static struct type structure_prototype = {
1798 .init = structure_init,
1799 .free = structure_free,
1800 .free_type = structure_free_type,
1801 .print_type_decl = structure_print_type,
1815 ###### free exec cases
1817 free_exec(cast(fieldref, e)->left);
1821 ###### variable grammar
1823 | Variable . IDENTIFIER ${ {
1824 struct fieldref *fr = new_pos(fieldref, $2);
1831 ###### print exec cases
1835 struct fieldref *f = cast(fieldref, e);
1836 print_exec(f->left, -1, bracket);
1837 printf(".%.*s", f->name.len, f->name.txt);
1841 ###### ast functions
1842 static int find_struct_index(struct type *type, struct text field)
1845 for (i = 0; i < type->structure.nfields; i++)
1846 if (text_cmp(type->structure.fields[i].name, field) == 0)
1851 ###### propagate exec cases
1855 struct fieldref *f = cast(fieldref, prog);
1856 struct type *st = propagate_types(f->left, c, ok, NULL, 0);
1859 type_err(c, "error: unknown type for field access", f->left,
1861 else if (st->init != structure_init)
1862 type_err(c, "error: field reference attempted on %1, not a struct",
1863 f->left, st, 0, NULL);
1864 else if (f->index == -2) {
1865 f->index = find_struct_index(st, f->name);
1867 type_err(c, "error: cannot find requested field in %1",
1868 f->left, st, 0, NULL);
1870 if (f->index >= 0) {
1871 struct type *ft = st->structure.fields[f->index].type;
1872 if (!type_compat(type, ft, rules))
1873 type_err(c, "error: have %1 but need %2", prog,
1880 ###### interp exec cases
1883 struct fieldref *f = cast(fieldref, e);
1885 struct value *lleft = linterp_exec(f->left, <ype);
1886 lrv = (void*)lleft->ptr + ltype->structure.fields[f->index].offset;
1887 rvtype = ltype->structure.fields[f->index].type;
1893 struct fieldlist *prev;
1897 ###### ast functions
1898 static void free_fieldlist(struct fieldlist *f)
1902 free_fieldlist(f->prev);
1904 free_value(f->f.type, f->f.init);
1910 ###### top level grammar
1911 DeclareStruct -> struct IDENTIFIER FieldBlock Newlines ${ {
1913 add_type(c, $2.txt, &structure_prototype);
1915 struct fieldlist *f;
1917 for (f = $3; f; f=f->prev)
1920 t->structure.nfields = cnt;
1921 t->structure.fields = calloc(cnt, sizeof(struct field));
1924 int a = f->f.type->align;
1926 t->structure.fields[cnt] = f->f;
1927 if (t->size & (a-1))
1928 t->size = (t->size | (a-1)) + 1;
1929 t->structure.fields[cnt].offset = t->size;
1930 t->size += ((f->f.type->size - 1) | (a-1)) + 1;
1939 FieldBlock -> { IN OptNL FieldLines OUT OptNL } ${ $0 = $<FL; }$
1940 | { SimpleFieldList } ${ $0 = $<SFL; }$
1941 | IN OptNL FieldLines OUT ${ $0 = $<FL; }$
1942 | SimpleFieldList EOL ${ $0 = $<SFL; }$
1944 FieldLines -> SimpleFieldList Newlines ${ $0 = $<SFL; }$
1945 | FieldLines SimpleFieldList Newlines ${
1950 SimpleFieldList -> Field ${ $0 = $<F; }$
1951 | SimpleFieldList ; Field ${
1955 | SimpleFieldList ; ${
1958 | ERROR ${ tok_err(c, "Syntax error in struct field", &$1); }$
1960 Field -> IDENTIFIER : Type = Expression ${ {
1963 $0 = calloc(1, sizeof(struct fieldlist));
1964 $0->f.name = $1.txt;
1969 propagate_types($<5, c, &ok, $3, 0);
1974 struct value vl = interp_exec($5, NULL);
1975 $0->f.init = val_alloc($0->f.type, &vl);
1978 | IDENTIFIER : Type ${
1979 $0 = calloc(1, sizeof(struct fieldlist));
1980 $0->f.name = $1.txt;
1982 $0->f.init = val_alloc($0->f.type, NULL);
1985 ###### forward decls
1986 static void structure_print_type(struct type *t, FILE *f);
1988 ###### value functions
1989 static void structure_print_type(struct type *t, FILE *f)
1993 fprintf(f, "struct %.*s\n", t->name.len, t->name.txt);
1995 for (i = 0; i < t->structure.nfields; i++) {
1996 struct field *fl = t->structure.fields + i;
1997 fprintf(f, " %.*s : ", fl->name.len, fl->name.txt);
1998 type_print(fl->type, f);
1999 if (fl->type->print && fl->init) {
2001 if (fl->type == Tstr)
2003 print_value(fl->type, fl->init);
2004 if (fl->type == Tstr)
2011 ###### print type decls
2016 while (target != 0) {
2018 for (t = context.typelist; t ; t=t->next)
2019 if (t->print_type_decl) {
2028 t->print_type_decl(t, stdout);
2034 ## Executables: the elements of code
2036 Each code element needs to be parsed, printed, analysed,
2037 interpreted, and freed. There are several, so let's just start with
2038 the easy ones and work our way up.
2042 We have already met values as separate objects. When manifest
2043 constants appear in the program text, that must result in an executable
2044 which has a constant value. So the `val` structure embeds a value in
2057 ###### ast functions
2058 struct val *new_val(struct type *T, struct token tk)
2060 struct val *v = new_pos(val, tk);
2069 $0 = new_val(Tbool, $1);
2073 $0 = new_val(Tbool, $1);
2077 $0 = new_val(Tnum, $1);
2080 if (number_parse($0->val.num, tail, $1.txt) == 0)
2081 mpq_init($0->val.num);
2083 tok_err(c, "error: unsupported number suffix",
2088 $0 = new_val(Tstr, $1);
2091 string_parse(&$1, '\\', &$0->val.str, tail);
2093 tok_err(c, "error: unsupported string suffix",
2098 $0 = new_val(Tstr, $1);
2101 string_parse(&$1, '\\', &$0->val.str, tail);
2103 tok_err(c, "error: unsupported string suffix",
2108 ###### print exec cases
2111 struct val *v = cast(val, e);
2112 if (v->vtype == Tstr)
2114 print_value(v->vtype, &v->val);
2115 if (v->vtype == Tstr)
2120 ###### propagate exec cases
2123 struct val *val = cast(val, prog);
2124 if (!type_compat(type, val->vtype, rules))
2125 type_err(c, "error: expected %1%r found %2",
2126 prog, type, rules, val->vtype);
2130 ###### interp exec cases
2132 rvtype = cast(val, e)->vtype;
2133 dup_value(rvtype, &cast(val, e)->val, &rv);
2136 ###### ast functions
2137 static void free_val(struct val *v)
2140 free_value(v->vtype, &v->val);
2144 ###### free exec cases
2145 case Xval: free_val(cast(val, e)); break;
2147 ###### ast functions
2148 // Move all nodes from 'b' to 'rv', reversing their order.
2149 // In 'b' 'left' is a list, and 'right' is the last node.
2150 // In 'rv', left' is the first node and 'right' is a list.
2151 static struct binode *reorder_bilist(struct binode *b)
2153 struct binode *rv = NULL;
2156 struct exec *t = b->right;
2160 b = cast(binode, b->left);
2170 Just as we used a `val` to wrap a value into an `exec`, we similarly
2171 need a `var` to wrap a `variable` into an exec. While each `val`
2172 contained a copy of the value, each `var` holds a link to the variable
2173 because it really is the same variable no matter where it appears.
2174 When a variable is used, we need to remember to follow the `->merged`
2175 link to find the primary instance.
2183 struct variable *var;
2189 VariableDecl -> IDENTIFIER : ${ {
2190 struct variable *v = var_decl(c, $1.txt);
2191 $0 = new_pos(var, $1);
2196 v = var_ref(c, $1.txt);
2198 type_err(c, "error: variable '%v' redeclared",
2200 type_err(c, "info: this is where '%v' was first declared",
2201 v->where_decl, NULL, 0, NULL);
2204 | IDENTIFIER :: ${ {
2205 struct variable *v = var_decl(c, $1.txt);
2206 $0 = new_pos(var, $1);
2212 v = var_ref(c, $1.txt);
2214 type_err(c, "error: variable '%v' redeclared",
2216 type_err(c, "info: this is where '%v' was first declared",
2217 v->where_decl, NULL, 0, NULL);
2220 | IDENTIFIER : Type ${ {
2221 struct variable *v = var_decl(c, $1.txt);
2222 $0 = new_pos(var, $1);
2230 v = var_ref(c, $1.txt);
2232 type_err(c, "error: variable '%v' redeclared",
2234 type_err(c, "info: this is where '%v' was first declared",
2235 v->where_decl, NULL, 0, NULL);
2238 | IDENTIFIER :: Type ${ {
2239 struct variable *v = var_decl(c, $1.txt);
2240 $0 = new_pos(var, $1);
2249 v = var_ref(c, $1.txt);
2251 type_err(c, "error: variable '%v' redeclared",
2253 type_err(c, "info: this is where '%v' was first declared",
2254 v->where_decl, NULL, 0, NULL);
2259 Variable -> IDENTIFIER ${ {
2260 struct variable *v = var_ref(c, $1.txt);
2261 $0 = new_pos(var, $1);
2263 /* This might be a label - allocate a var just in case */
2264 v = var_decl(c, $1.txt);
2272 cast(var, $0)->var = v;
2277 Type -> IDENTIFIER ${
2278 $0 = find_type(c, $1.txt);
2281 "error: undefined type", &$1);
2288 ###### print exec cases
2291 struct var *v = cast(var, e);
2293 struct binding *b = v->var->name;
2294 printf("%.*s", b->name.len, b->name.txt);
2301 if (loc->type == Xvar) {
2302 struct var *v = cast(var, loc);
2304 struct binding *b = v->var->name;
2305 fprintf(stderr, "%.*s", b->name.len, b->name.txt);
2307 fputs("???", stderr); // NOTEST
2309 fputs("NOTVAR", stderr); // NOTEST
2312 ###### propagate exec cases
2316 struct var *var = cast(var, prog);
2317 struct variable *v = var->var;
2319 type_err(c, "%d:BUG: no variable!!", prog, NULL, 0, NULL); // NOTEST
2320 return Tnone; // NOTEST
2324 if (v->constant && (rules & Rnoconstant)) {
2325 type_err(c, "error: Cannot assign to a constant: %v",
2326 prog, NULL, 0, NULL);
2327 type_err(c, "info: name was defined as a constant here",
2328 v->where_decl, NULL, 0, NULL);
2331 if (v->type == Tnone && v->where_decl == prog)
2332 type_err(c, "error: variable used but not declared: %v",
2333 prog, NULL, 0, NULL);
2334 if (v->type == NULL) {
2335 if (type && *ok != 0) {
2338 v->where_set = prog;
2343 if (!type_compat(type, v->type, rules)) {
2344 type_err(c, "error: expected %1%r but variable '%v' is %2", prog,
2345 type, rules, v->type);
2346 type_err(c, "info: this is where '%v' was set to %1", v->where_set,
2347 v->type, rules, NULL);
2354 ###### interp exec cases
2357 struct var *var = cast(var, e);
2358 struct variable *v = var->var;
2367 ###### ast functions
2369 static void free_var(struct var *v)
2374 ###### free exec cases
2375 case Xvar: free_var(cast(var, e)); break;
2377 ### Expressions: Conditional
2379 Our first user of the `binode` will be conditional expressions, which
2380 is a bit odd as they actually have three components. That will be
2381 handled by having 2 binodes for each expression. The conditional
2382 expression is the lowest precedence operator which is why we define it
2383 first - to start the precedence list.
2385 Conditional expressions are of the form "value `if` condition `else`
2386 other_value". They associate to the right, so everything to the right
2387 of `else` is part of an else value, while only a higher-precedence to
2388 the left of `if` is the if values. Between `if` and `else` there is no
2389 room for ambiguity, so a full conditional expression is allowed in
2401 Expression -> Expression if Expression else Expression $$ifelse ${ {
2402 struct binode *b1 = new(binode);
2403 struct binode *b2 = new(binode);
2412 ## expression grammar
2414 ###### print binode cases
2417 b2 = cast(binode, b->right);
2418 if (bracket) printf("(");
2419 print_exec(b2->left, -1, bracket);
2421 print_exec(b->left, -1, bracket);
2423 print_exec(b2->right, -1, bracket);
2424 if (bracket) printf(")");
2427 ###### propagate binode cases
2430 /* cond must be Tbool, others must match */
2431 struct binode *b2 = cast(binode, b->right);
2434 propagate_types(b->left, c, ok, Tbool, 0);
2435 t = propagate_types(b2->left, c, ok, type, Rnolabel);
2436 t2 = propagate_types(b2->right, c, ok, type ?: t, Rnolabel);
2440 ###### interp binode cases
2443 struct binode *b2 = cast(binode, b->right);
2444 left = interp_exec(b->left, <ype);
2446 rv = interp_exec(b2->left, &rvtype);
2448 rv = interp_exec(b2->right, &rvtype);
2452 ### Expressions: Boolean
2454 The next class of expressions to use the `binode` will be Boolean
2455 expressions. "`and then`" and "`or else`" are similar to `and` and `or`
2456 have same corresponding precendence. The difference is that they don't
2457 evaluate the second expression if not necessary.
2466 ###### expr precedence
2471 ###### expression grammar
2472 | Expression or Expression ${ {
2473 struct binode *b = new(binode);
2479 | Expression or else Expression ${ {
2480 struct binode *b = new(binode);
2487 | Expression and Expression ${ {
2488 struct binode *b = new(binode);
2494 | Expression and then Expression ${ {
2495 struct binode *b = new(binode);
2502 | not Expression ${ {
2503 struct binode *b = new(binode);
2509 ###### print binode cases
2511 if (bracket) printf("(");
2512 print_exec(b->left, -1, bracket);
2514 print_exec(b->right, -1, bracket);
2515 if (bracket) printf(")");
2518 if (bracket) printf("(");
2519 print_exec(b->left, -1, bracket);
2520 printf(" and then ");
2521 print_exec(b->right, -1, bracket);
2522 if (bracket) printf(")");
2525 if (bracket) printf("(");
2526 print_exec(b->left, -1, bracket);
2528 print_exec(b->right, -1, bracket);
2529 if (bracket) printf(")");
2532 if (bracket) printf("(");
2533 print_exec(b->left, -1, bracket);
2534 printf(" or else ");
2535 print_exec(b->right, -1, bracket);
2536 if (bracket) printf(")");
2539 if (bracket) printf("(");
2541 print_exec(b->right, -1, bracket);
2542 if (bracket) printf(")");
2545 ###### propagate binode cases
2551 /* both must be Tbool, result is Tbool */
2552 propagate_types(b->left, c, ok, Tbool, 0);
2553 propagate_types(b->right, c, ok, Tbool, 0);
2554 if (type && type != Tbool)
2555 type_err(c, "error: %1 operation found where %2 expected", prog,
2559 ###### interp binode cases
2561 rv = interp_exec(b->left, &rvtype);
2562 right = interp_exec(b->right, &rtype);
2563 rv.bool = rv.bool && right.bool;
2566 rv = interp_exec(b->left, &rvtype);
2568 rv = interp_exec(b->right, NULL);
2571 rv = interp_exec(b->left, &rvtype);
2572 right = interp_exec(b->right, &rtype);
2573 rv.bool = rv.bool || right.bool;
2576 rv = interp_exec(b->left, &rvtype);
2578 rv = interp_exec(b->right, NULL);
2581 rv = interp_exec(b->right, &rvtype);
2585 ### Expressions: Comparison
2587 Of slightly higher precedence that Boolean expressions are Comparisons.
2588 A comparison takes arguments of any comparable type, but the two types
2591 To simplify the parsing we introduce an `eop` which can record an
2592 expression operator, and the `CMPop` non-terminal will match one of them.
2599 ###### ast functions
2600 static void free_eop(struct eop *e)
2614 ###### expr precedence
2615 $LEFT < > <= >= == != CMPop
2617 ###### expression grammar
2618 | Expression CMPop Expression ${ {
2619 struct binode *b = new(binode);
2629 CMPop -> < ${ $0.op = Less; }$
2630 | > ${ $0.op = Gtr; }$
2631 | <= ${ $0.op = LessEq; }$
2632 | >= ${ $0.op = GtrEq; }$
2633 | == ${ $0.op = Eql; }$
2634 | != ${ $0.op = NEql; }$
2636 ###### print binode cases
2644 if (bracket) printf("(");
2645 print_exec(b->left, -1, bracket);
2647 case Less: printf(" < "); break;
2648 case LessEq: printf(" <= "); break;
2649 case Gtr: printf(" > "); break;
2650 case GtrEq: printf(" >= "); break;
2651 case Eql: printf(" == "); break;
2652 case NEql: printf(" != "); break;
2653 default: abort(); // NOTEST
2655 print_exec(b->right, -1, bracket);
2656 if (bracket) printf(")");
2659 ###### propagate binode cases
2666 /* Both must match but not be labels, result is Tbool */
2667 t = propagate_types(b->left, c, ok, NULL, Rnolabel);
2669 propagate_types(b->right, c, ok, t, 0);
2671 t = propagate_types(b->right, c, ok, NULL, Rnolabel);
2673 t = propagate_types(b->left, c, ok, t, 0);
2675 if (!type_compat(type, Tbool, 0))
2676 type_err(c, "error: Comparison returns %1 but %2 expected", prog,
2677 Tbool, rules, type);
2680 ###### interp binode cases
2689 left = interp_exec(b->left, <ype);
2690 right = interp_exec(b->right, &rtype);
2691 cmp = value_cmp(ltype, rtype, &left, &right);
2694 case Less: rv.bool = cmp < 0; break;
2695 case LessEq: rv.bool = cmp <= 0; break;
2696 case Gtr: rv.bool = cmp > 0; break;
2697 case GtrEq: rv.bool = cmp >= 0; break;
2698 case Eql: rv.bool = cmp == 0; break;
2699 case NEql: rv.bool = cmp != 0; break;
2700 default: rv.bool = 0; break; // NOTEST
2705 ### Expressions: The rest
2707 The remaining expressions with the highest precedence are arithmetic,
2708 string concatenation, and string conversion. String concatenation
2709 (`++`) has the same precedence as multiplication and division, but lower
2712 String conversion is a temporary feature until I get a better type
2713 system. `$` is a prefix operator which expects a string and returns
2716 `+` and `-` are both infix and prefix operations (where they are
2717 absolute value and negation). These have different operator names.
2719 We also have a 'Bracket' operator which records where parentheses were
2720 found. This makes it easy to reproduce these when printing. Possibly I
2721 should only insert brackets were needed for precedence.
2731 ###### expr precedence
2737 ###### expression grammar
2738 | Expression Eop Expression ${ {
2739 struct binode *b = new(binode);
2746 | Expression Top Expression ${ {
2747 struct binode *b = new(binode);
2754 | ( Expression ) ${ {
2755 struct binode *b = new_pos(binode, $1);
2760 | Uop Expression ${ {
2761 struct binode *b = new(binode);
2766 | Value ${ $0 = $<1; }$
2767 | Variable ${ $0 = $<1; }$
2770 Eop -> + ${ $0.op = Plus; }$
2771 | - ${ $0.op = Minus; }$
2773 Uop -> + ${ $0.op = Absolute; }$
2774 | - ${ $0.op = Negate; }$
2775 | $ ${ $0.op = StringConv; }$
2777 Top -> * ${ $0.op = Times; }$
2778 | / ${ $0.op = Divide; }$
2779 | % ${ $0.op = Rem; }$
2780 | ++ ${ $0.op = Concat; }$
2782 ###### print binode cases
2789 if (bracket) printf("(");
2790 print_exec(b->left, indent, bracket);
2792 case Plus: fputs(" + ", stdout); break;
2793 case Minus: fputs(" - ", stdout); break;
2794 case Times: fputs(" * ", stdout); break;
2795 case Divide: fputs(" / ", stdout); break;
2796 case Rem: fputs(" % ", stdout); break;
2797 case Concat: fputs(" ++ ", stdout); break;
2798 default: abort(); // NOTEST
2800 print_exec(b->right, indent, bracket);
2801 if (bracket) printf(")");
2806 if (bracket) printf("(");
2808 case Absolute: fputs("+", stdout); break;
2809 case Negate: fputs("-", stdout); break;
2810 case StringConv: fputs("$", stdout); break;
2811 default: abort(); // NOTEST
2813 print_exec(b->right, indent, bracket);
2814 if (bracket) printf(")");
2818 print_exec(b->right, indent, bracket);
2822 ###### propagate binode cases
2828 /* both must be numbers, result is Tnum */
2831 /* as propagate_types ignores a NULL,
2832 * unary ops fit here too */
2833 propagate_types(b->left, c, ok, Tnum, 0);
2834 propagate_types(b->right, c, ok, Tnum, 0);
2835 if (!type_compat(type, Tnum, 0))
2836 type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
2841 /* both must be Tstr, result is Tstr */
2842 propagate_types(b->left, c, ok, Tstr, 0);
2843 propagate_types(b->right, c, ok, Tstr, 0);
2844 if (!type_compat(type, Tstr, 0))
2845 type_err(c, "error: Concat returns %1 but %2 expected", prog,
2850 /* op must be string, result is number */
2851 propagate_types(b->left, c, ok, Tstr, 0);
2852 if (!type_compat(type, Tnum, 0))
2854 "error: Can only convert string to number, not %1",
2855 prog, type, 0, NULL);
2859 return propagate_types(b->right, c, ok, type, 0);
2861 ###### interp binode cases
2864 rv = interp_exec(b->left, &rvtype);
2865 right = interp_exec(b->right, &rtype);
2866 mpq_add(rv.num, rv.num, right.num);
2869 rv = interp_exec(b->left, &rvtype);
2870 right = interp_exec(b->right, &rtype);
2871 mpq_sub(rv.num, rv.num, right.num);
2874 rv = interp_exec(b->left, &rvtype);
2875 right = interp_exec(b->right, &rtype);
2876 mpq_mul(rv.num, rv.num, right.num);
2879 rv = interp_exec(b->left, &rvtype);
2880 right = interp_exec(b->right, &rtype);
2881 mpq_div(rv.num, rv.num, right.num);
2886 left = interp_exec(b->left, <ype);
2887 right = interp_exec(b->right, &rtype);
2888 mpz_init(l); mpz_init(r); mpz_init(rem);
2889 mpz_tdiv_q(l, mpq_numref(left.num), mpq_denref(left.num));
2890 mpz_tdiv_q(r, mpq_numref(right.num), mpq_denref(right.num));
2891 mpz_tdiv_r(rem, l, r);
2892 val_init(Tnum, &rv);
2893 mpq_set_z(rv.num, rem);
2894 mpz_clear(r); mpz_clear(l); mpz_clear(rem);
2899 rv = interp_exec(b->right, &rvtype);
2900 mpq_neg(rv.num, rv.num);
2903 rv = interp_exec(b->right, &rvtype);
2904 mpq_abs(rv.num, rv.num);
2907 rv = interp_exec(b->right, &rvtype);
2910 left = interp_exec(b->left, <ype);
2911 right = interp_exec(b->right, &rtype);
2913 rv.str = text_join(left.str, right.str);
2916 right = interp_exec(b->right, &rvtype);
2920 struct text tx = right.str;
2923 if (tx.txt[0] == '-') {
2928 if (number_parse(rv.num, tail, tx) == 0)
2931 mpq_neg(rv.num, rv.num);
2933 printf("Unsupported suffix: %.*s\n", tx.len, tx.txt);
2937 ###### value functions
2939 static struct text text_join(struct text a, struct text b)
2942 rv.len = a.len + b.len;
2943 rv.txt = malloc(rv.len);
2944 memcpy(rv.txt, a.txt, a.len);
2945 memcpy(rv.txt+a.len, b.txt, b.len);
2949 ### Blocks, Statements, and Statement lists.
2951 Now that we have expressions out of the way we need to turn to
2952 statements. There are simple statements and more complex statements.
2953 Simple statements do not contain (syntactic) newlines, complex statements do.
2955 Statements often come in sequences and we have corresponding simple
2956 statement lists and complex statement lists.
2957 The former comprise only simple statements separated by semicolons.
2958 The later comprise complex statements and simple statement lists. They are
2959 separated by newlines. Thus the semicolon is only used to separate
2960 simple statements on the one line. This may be overly restrictive,
2961 but I'm not sure I ever want a complex statement to share a line with
2964 Note that a simple statement list can still use multiple lines if
2965 subsequent lines are indented, so
2967 ###### Example: wrapped simple statement list
2972 is a single simple statement list. This might allow room for
2973 confusion, so I'm not set on it yet.
2975 A simple statement list needs no extra syntax. A complex statement
2976 list has two syntactic forms. It can be enclosed in braces (much like
2977 C blocks), or it can be introduced by an indent and continue until an
2978 unindented newline (much like Python blocks). With this extra syntax
2979 it is referred to as a block.
2981 Note that a block does not have to include any newlines if it only
2982 contains simple statements. So both of:
2984 if condition: a=b; d=f
2986 if condition { a=b; print f }
2990 In either case the list is constructed from a `binode` list with
2991 `Block` as the operator. When parsing the list it is most convenient
2992 to append to the end, so a list is a list and a statement. When using
2993 the list it is more convenient to consider a list to be a statement
2994 and a list. So we need a function to re-order a list.
2995 `reorder_bilist` serves this purpose.
2997 The only stand-alone statement we introduce at this stage is `pass`
2998 which does nothing and is represented as a `NULL` pointer in a `Block`
2999 list. Other stand-alone statements will follow once the infrastructure
3005 ###### expr precedence
3011 Block -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3012 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3013 | SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3014 | SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3015 | IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3017 OpenBlock -> OpenScope { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3018 | OpenScope { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3019 | OpenScope SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3020 | OpenScope SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3021 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3023 UseBlock -> { OpenScope IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3024 | { OpenScope SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3025 | IN OpenScope OptNL Statementlist OUT ${ $0 = $<Sl; }$
3027 ColonBlock -> { IN OptNL Statementlist OUT OptNL } ${ $0 = $<Sl; }$
3028 | { SimpleStatements } ${ $0 = reorder_bilist($<SS); }$
3029 | : SimpleStatements ; ${ $0 = reorder_bilist($<SS); }$
3030 | : SimpleStatements EOL ${ $0 = reorder_bilist($<SS); }$
3031 | : IN OptNL Statementlist OUT ${ $0 = $<Sl; }$
3033 Statementlist -> ComplexStatements ${ $0 = reorder_bilist($<CS); }$
3035 ComplexStatements -> ComplexStatements ComplexStatement ${
3045 | ComplexStatement ${
3057 ComplexStatement -> SimpleStatements Newlines ${
3058 $0 = reorder_bilist($<SS);
3060 | SimpleStatements ; Newlines ${
3061 $0 = reorder_bilist($<SS);
3063 ## ComplexStatement Grammar
3066 SimpleStatements -> SimpleStatements ; SimpleStatement ${
3072 | SimpleStatement ${
3079 SimpleStatement -> pass ${ $0 = NULL; }$
3080 | ERROR ${ tok_err(c, "Syntax error in statement", &$1); }$
3081 ## SimpleStatement Grammar
3083 ###### print binode cases
3087 if (b->left == NULL)
3090 print_exec(b->left, indent, bracket);
3093 print_exec(b->right, indent, bracket);
3096 // block, one per line
3097 if (b->left == NULL)
3098 do_indent(indent, "pass\n");
3100 print_exec(b->left, indent, bracket);
3102 print_exec(b->right, indent, bracket);
3106 ###### propagate binode cases
3109 /* If any statement returns something other than Tnone
3110 * or Tbool then all such must return same type.
3111 * As each statement may be Tnone or something else,
3112 * we must always pass NULL (unknown) down, otherwise an incorrect
3113 * error might occur. We never return Tnone unless it is
3118 for (e = b; e; e = cast(binode, e->right)) {
3119 t = propagate_types(e->left, c, ok, NULL, rules);
3120 if ((rules & Rboolok) && t == Tbool)
3122 if (t && t != Tnone && t != Tbool) {
3126 type_err(c, "error: expected %1%r, found %2",
3127 e->left, type, rules, t);
3133 ###### interp binode cases
3135 while (rvtype == Tnone &&
3138 rv = interp_exec(b->left, &rvtype);
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 ##### expr precedence
3158 ###### SimpleStatement Grammar
3160 | print ExpressionList ${
3161 $0 = reorder_bilist($<2);
3163 | print ExpressionList , ${
3168 $0 = reorder_bilist($0);
3179 ExpressionList -> ExpressionList , Expression ${
3192 ###### print binode cases
3195 do_indent(indent, "print");
3199 print_exec(b->left, -1, bracket);
3203 b = cast(binode, b->right);
3209 ###### propagate binode cases
3212 /* don't care but all must be consistent */
3213 propagate_types(b->left, c, ok, NULL, Rnolabel);
3214 propagate_types(b->right, c, ok, NULL, Rnolabel);
3217 ###### interp binode cases
3223 for ( ; b; b = cast(binode, b->right))
3227 left = interp_exec(b->left, <ype);
3228 print_value(ltype, &left);
3229 free_value(ltype, &left);
3240 ###### Assignment statement
3242 An assignment will assign a value to a variable, providing it hasn't
3243 been declared as a constant. The analysis phase ensures that the type
3244 will be correct so the interpreter just needs to perform the
3245 calculation. There is a form of assignment which declares a new
3246 variable as well as assigning a value. If a name is assigned before
3247 it is declared, and error will be raised as the name is created as
3248 `Tlabel` and it is illegal to assign to such names.
3254 ###### SimpleStatement Grammar
3255 | Variable = Expression ${
3261 | VariableDecl = Expression ${
3269 if ($1->var->where_set == NULL) {
3271 "Variable declared with no type or value: %v",
3281 ###### print binode cases
3284 do_indent(indent, "");
3285 print_exec(b->left, indent, bracket);
3287 print_exec(b->right, indent, bracket);
3294 struct variable *v = cast(var, b->left)->var;
3295 do_indent(indent, "");
3296 print_exec(b->left, indent, bracket);
3297 if (cast(var, b->left)->var->constant) {
3298 if (v->where_decl == v->where_set) {
3300 type_print(v->type, stdout);
3305 if (v->where_decl == v->where_set) {
3307 type_print(v->type, stdout);
3314 print_exec(b->right, indent, bracket);
3321 ###### propagate binode cases
3325 /* Both must match and not be labels,
3326 * Type must support 'dup',
3327 * For Assign, left must not be constant.
3330 t = propagate_types(b->left, c, ok, NULL,
3331 Rnolabel | (b->op == Assign ? Rnoconstant : 0));
3336 if (propagate_types(b->right, c, ok, t, 0) != t)
3337 if (b->left->type == Xvar)
3338 type_err(c, "info: variable '%v' was set as %1 here.",
3339 cast(var, b->left)->var->where_set, t, rules, NULL);
3341 t = propagate_types(b->right, c, ok, NULL, Rnolabel);
3343 propagate_types(b->left, c, ok, t,
3344 (b->op == Assign ? Rnoconstant : 0));
3346 if (t && t->dup == NULL)
3347 type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
3352 ###### interp binode cases
3355 lleft = linterp_exec(b->left, <ype);
3356 right = interp_exec(b->right, &rtype);
3358 free_value(ltype, lleft);
3359 dup_value(ltype, &right, lleft);
3366 struct variable *v = cast(var, b->left)->var;
3370 right = interp_exec(b->right, &rtype);
3371 free_value(v->type, v->val);
3373 v->val = val_alloc(v->type, &right);
3376 free_value(v->type, v->val);
3377 v->val = val_alloc(v->type, NULL);
3382 ### The `use` statement
3384 The `use` statement is the last "simple" statement. It is needed when
3385 the condition in a conditional statement is a block. `use` works much
3386 like `return` in C, but only completes the `condition`, not the whole
3392 ###### expr precedence
3395 ###### SimpleStatement Grammar
3397 $0 = new_pos(binode, $1);
3400 if ($0->right->type == Xvar) {
3401 struct var *v = cast(var, $0->right);
3402 if (v->var->type == Tnone) {
3403 /* Convert this to a label */
3404 v->var->type = Tlabel;
3405 v->var->val = val_alloc(Tlabel, NULL);
3406 v->var->val->label = v->var->val;
3411 ###### print binode cases
3414 do_indent(indent, "use ");
3415 print_exec(b->right, -1, bracket);
3420 ###### propagate binode cases
3423 /* result matches value */
3424 return propagate_types(b->right, c, ok, type, 0);
3426 ###### interp binode cases
3429 rv = interp_exec(b->right, &rvtype);
3432 ### The Conditional Statement
3434 This is the biggy and currently the only complex statement. This
3435 subsumes `if`, `while`, `do/while`, `switch`, and some parts of `for`.
3436 It is comprised of a number of parts, all of which are optional though
3437 set combinations apply. Each part is (usually) a key word (`then` is
3438 sometimes optional) followed by either an expression or a code block,
3439 except the `casepart` which is a "key word and an expression" followed
3440 by a code block. The code-block option is valid for all parts and,
3441 where an expression is also allowed, the code block can use the `use`
3442 statement to report a value. If the code block does not report a value
3443 the effect is similar to reporting `True`.
3445 The `else` and `case` parts, as well as `then` when combined with
3446 `if`, can contain a `use` statement which will apply to some
3447 containing conditional statement. `for` parts, `do` parts and `then`
3448 parts used with `for` can never contain a `use`, except in some
3449 subordinate conditional statement.
3451 If there is a `forpart`, it is executed first, only once.
3452 If there is a `dopart`, then it is executed repeatedly providing
3453 always that the `condpart` or `cond`, if present, does not return a non-True
3454 value. `condpart` can fail to return any value if it simply executes
3455 to completion. This is treated the same as returning `True`.
3457 If there is a `thenpart` it will be executed whenever the `condpart`
3458 or `cond` returns True (or does not return any value), but this will happen
3459 *after* `dopart` (when present).
3461 If `elsepart` is present it will be executed at most once when the
3462 condition returns `False` or some value that isn't `True` and isn't
3463 matched by any `casepart`. If there are any `casepart`s, they will be
3464 executed when the condition returns a matching value.
3466 The particular sorts of values allowed in case parts has not yet been
3467 determined in the language design, so nothing is prohibited.
3469 The various blocks in this complex statement potentially provide scope
3470 for variables as described earlier. Each such block must include the
3471 "OpenScope" nonterminal before parsing the block, and must call
3472 `var_block_close()` when closing the block.
3474 The code following "`if`", "`switch`" and "`for`" does not get its own
3475 scope, but is in a scope covering the whole statement, so names
3476 declared there cannot be redeclared elsewhere. Similarly the
3477 condition following "`while`" is in a scope the covers the body
3478 ("`do`" part) of the loop, and which does not allow conditional scope
3479 extension. Code following "`then`" (both looping and non-looping),
3480 "`else`" and "`case`" each get their own local scope.
3482 The type requirements on the code block in a `whilepart` are quite
3483 unusal. It is allowed to return a value of some identifiable type, in
3484 which case the loop aborts and an appropriate `casepart` is run, or it
3485 can return a Boolean, in which case the loop either continues to the
3486 `dopart` (on `True`) or aborts and runs the `elsepart` (on `False`).
3487 This is different both from the `ifpart` code block which is expected to
3488 return a Boolean, or the `switchpart` code block which is expected to
3489 return the same type as the casepart values. The correct analysis of
3490 the type of the `whilepart` code block is the reason for the
3491 `Rboolok` flag which is passed to `propagate_types()`.
3493 The `cond_statement` cannot fit into a `binode` so a new `exec` is
3502 struct exec *action;
3503 struct casepart *next;
3505 struct cond_statement {
3507 struct exec *forpart, *condpart, *dopart, *thenpart, *elsepart;
3508 struct casepart *casepart;
3511 ###### ast functions
3513 static void free_casepart(struct casepart *cp)
3517 free_exec(cp->value);
3518 free_exec(cp->action);
3525 static void free_cond_statement(struct cond_statement *s)
3529 free_exec(s->forpart);
3530 free_exec(s->condpart);
3531 free_exec(s->dopart);
3532 free_exec(s->thenpart);
3533 free_exec(s->elsepart);
3534 free_casepart(s->casepart);
3538 ###### free exec cases
3539 case Xcond_statement: free_cond_statement(cast(cond_statement, e)); break;
3541 ###### ComplexStatement Grammar
3542 | CondStatement ${ $0 = $<1; }$
3544 ###### expr precedence
3545 $TERM for then while do
3552 // A CondStatement must end with EOL, as does CondSuffix and
3554 // ForPart, ThenPart, SwitchPart, CasePart are non-empty and
3555 // may or may not end with EOL
3556 // WhilePart and IfPart include an appropriate Suffix
3559 // Both ForPart and Whilepart open scopes, and CondSuffix only
3560 // closes one - so in the first branch here we have another to close.
3561 CondStatement -> ForPart OptNL ThenPart OptNL WhilePart CondSuffix ${
3564 $0->thenpart = $<TP;
3565 $0->condpart = $WP.condpart; $WP.condpart = NULL;
3566 $0->dopart = $WP.dopart; $WP.dopart = NULL;
3567 var_block_close(c, CloseSequential);
3569 | ForPart OptNL WhilePart CondSuffix ${
3572 $0->condpart = $WP.condpart; $WP.condpart = NULL;
3573 $0->dopart = $WP.dopart; $WP.dopart = NULL;
3574 var_block_close(c, CloseSequential);
3576 | WhilePart CondSuffix ${
3578 $0->condpart = $WP.condpart; $WP.condpart = NULL;
3579 $0->dopart = $WP.dopart; $WP.dopart = NULL;
3581 | SwitchPart OptNL CasePart CondSuffix ${
3583 $0->condpart = $<SP;
3584 $CP->next = $0->casepart;
3585 $0->casepart = $<CP;
3587 | SwitchPart : IN OptNL CasePart CondSuffix OUT Newlines ${
3589 $0->condpart = $<SP;
3590 $CP->next = $0->casepart;
3591 $0->casepart = $<CP;
3593 | IfPart IfSuffix ${
3595 $0->condpart = $IP.condpart; $IP.condpart = NULL;
3596 $0->thenpart = $IP.thenpart; $IP.thenpart = NULL;
3597 // This is where we close an "if" statement
3598 var_block_close(c, CloseSequential);
3601 CondSuffix -> IfSuffix ${
3603 // This is where we close scope of the whole
3604 // "for" or "while" statement
3605 var_block_close(c, CloseSequential);
3607 | Newlines CasePart CondSuffix ${
3609 $CP->next = $0->casepart;
3610 $0->casepart = $<CP;
3612 | CasePart CondSuffix ${
3614 $CP->next = $0->casepart;
3615 $0->casepart = $<CP;
3618 IfSuffix -> Newlines ${ $0 = new(cond_statement); }$
3619 | Newlines ElsePart ${ $0 = $<EP; }$
3620 | ElsePart ${$0 = $<EP; }$
3622 ElsePart -> else OpenBlock Newlines ${
3623 $0 = new(cond_statement);
3624 $0->elsepart = $<OB;
3625 var_block_close(c, CloseElse);
3627 | else OpenScope CondStatement ${
3628 $0 = new(cond_statement);
3629 $0->elsepart = $<CS;
3630 var_block_close(c, CloseElse);
3634 CasePart -> case Expression OpenScope ColonBlock ${
3635 $0 = calloc(1,sizeof(struct casepart));
3638 var_block_close(c, CloseParallel);
3642 // These scopes are closed in CondSuffix
3643 ForPart -> for OpenBlock ${
3647 ThenPart -> then OpenBlock ${
3649 var_block_close(c, CloseSequential);
3653 // This scope is closed in CondSuffix
3654 WhilePart -> while UseBlock OptNL do Block ${
3658 | while OpenScope Expression ColonBlock ${
3659 $0.condpart = $<Exp;
3663 IfPart -> if UseBlock OptNL then OpenBlock ClosePara ${
3667 | if OpenScope Expression OpenScope ColonBlock ClosePara ${
3671 | if OpenScope Expression OpenScope OptNL then Block ClosePara ${
3677 // This scope is closed in CondSuffix
3678 SwitchPart -> switch OpenScope Expression ${
3681 | switch UseBlock ${
3685 ###### print exec cases
3687 case Xcond_statement:
3689 struct cond_statement *cs = cast(cond_statement, e);
3690 struct casepart *cp;
3692 do_indent(indent, "for");
3693 if (bracket) printf(" {\n"); else printf("\n");
3694 print_exec(cs->forpart, indent+1, bracket);
3697 do_indent(indent, "} then {\n");
3699 do_indent(indent, "then\n");
3700 print_exec(cs->thenpart, indent+1, bracket);
3702 if (bracket) do_indent(indent, "}\n");
3706 if (cs->condpart && cs->condpart->type == Xbinode &&
3707 cast(binode, cs->condpart)->op == Block) {
3709 do_indent(indent, "while {\n");
3711 do_indent(indent, "while\n");
3712 print_exec(cs->condpart, indent+1, bracket);
3714 do_indent(indent, "} do {\n");
3716 do_indent(indent, "do\n");
3717 print_exec(cs->dopart, indent+1, bracket);
3719 do_indent(indent, "}\n");
3721 do_indent(indent, "while ");
3722 print_exec(cs->condpart, 0, bracket);
3727 print_exec(cs->dopart, indent+1, bracket);
3729 do_indent(indent, "}\n");
3734 do_indent(indent, "switch");
3736 do_indent(indent, "if");
3737 if (cs->condpart && cs->condpart->type == Xbinode &&
3738 cast(binode, cs->condpart)->op == Block) {
3743 print_exec(cs->condpart, indent+1, bracket);
3745 do_indent(indent, "}\n");
3747 do_indent(indent, "then:\n");
3748 print_exec(cs->thenpart, indent+1, bracket);
3752 print_exec(cs->condpart, 0, bracket);
3758 print_exec(cs->thenpart, indent+1, bracket);
3760 do_indent(indent, "}\n");
3765 for (cp = cs->casepart; cp; cp = cp->next) {
3766 do_indent(indent, "case ");
3767 print_exec(cp->value, -1, 0);
3772 print_exec(cp->action, indent+1, bracket);
3774 do_indent(indent, "}\n");
3777 do_indent(indent, "else");
3782 print_exec(cs->elsepart, indent+1, bracket);
3784 do_indent(indent, "}\n");
3789 ###### propagate exec cases
3790 case Xcond_statement:
3792 // forpart and dopart must return Tnone
3793 // thenpart must return Tnone if there is a dopart,
3794 // otherwise it is like elsepart.
3796 // be bool if there is no casepart
3797 // match casepart->values if there is a switchpart
3798 // either be bool or match casepart->value if there
3800 // elsepart and casepart->action must match the return type
3801 // expected of this statement.
3802 struct cond_statement *cs = cast(cond_statement, prog);
3803 struct casepart *cp;
3805 t = propagate_types(cs->forpart, c, ok, Tnone, 0);
3806 if (!type_compat(Tnone, t, 0))
3808 t = propagate_types(cs->dopart, c, ok, Tnone, 0);
3809 if (!type_compat(Tnone, t, 0))
3812 t = propagate_types(cs->thenpart, c, ok, Tnone, 0);
3813 if (!type_compat(Tnone, t, 0))
3816 if (cs->casepart == NULL)
3817 propagate_types(cs->condpart, c, ok, Tbool, 0);
3819 /* Condpart must match case values, with bool permitted */
3821 for (cp = cs->casepart;
3822 cp && !t; cp = cp->next)
3823 t = propagate_types(cp->value, c, ok, NULL, 0);
3824 if (!t && cs->condpart)
3825 t = propagate_types(cs->condpart, c, ok, NULL, Rboolok);
3826 // Now we have a type (I hope) push it down
3828 for (cp = cs->casepart; cp; cp = cp->next)
3829 propagate_types(cp->value, c, ok, t, 0);
3830 propagate_types(cs->condpart, c, ok, t, Rboolok);
3833 // (if)then, else, and case parts must return expected type.
3834 if (!cs->dopart && !type)
3835 type = propagate_types(cs->thenpart, c, ok, NULL, rules);
3837 type = propagate_types(cs->elsepart, c, ok, NULL, rules);
3838 for (cp = cs->casepart;
3841 type = propagate_types(cp->action, c, ok, NULL, rules);
3844 propagate_types(cs->thenpart, c, ok, type, rules);
3845 propagate_types(cs->elsepart, c, ok, type, rules);
3846 for (cp = cs->casepart; cp ; cp = cp->next)
3847 propagate_types(cp->action, c, ok, type, rules);
3853 ###### interp exec cases
3854 case Xcond_statement:
3856 struct value v, cnd;
3857 struct type *vtype, *cndtype;
3858 struct casepart *cp;
3859 struct cond_statement *c = cast(cond_statement, e);
3862 interp_exec(c->forpart, NULL);
3865 cnd = interp_exec(c->condpart, &cndtype);
3868 if (!(cndtype == Tnone ||
3869 (cndtype == Tbool && cnd.bool != 0)))
3871 // cnd is Tnone or Tbool, doesn't need to be freed
3873 interp_exec(c->dopart, NULL);
3876 rv = interp_exec(c->thenpart, &rvtype);
3877 if (rvtype != Tnone || !c->dopart)
3879 free_value(rvtype, &rv);
3882 } while (c->dopart);
3884 for (cp = c->casepart; cp; cp = cp->next) {
3885 v = interp_exec(cp->value, &vtype);
3886 if (value_cmp(cndtype, vtype, &v, &cnd) == 0) {
3887 free_value(vtype, &v);
3888 free_value(cndtype, &cnd);
3889 rv = interp_exec(cp->action, &rvtype);
3892 free_value(vtype, &v);
3894 free_value(cndtype, &cnd);
3896 rv = interp_exec(c->elsepart, &rvtype);
3903 ### Top level structure
3905 All the language elements so far can be used in various places. Now
3906 it is time to clarify what those places are.
3908 At the top level of a file there will be a number of declarations.
3909 Many of the things that can be declared haven't been described yet,
3910 such as functions, procedures, imports, and probably more.
3911 For now there are two sorts of things that can appear at the top
3912 level. They are predefined constants, `struct` types, and the main
3913 program. While the syntax will allow the main program to appear
3914 multiple times, that will trigger an error if it is actually attempted.
3916 The various declarations do not return anything. They store the
3917 various declarations in the parse context.
3919 ###### Parser: grammar
3922 Ocean -> OptNL DeclarationList
3929 DeclarationList -> Declaration
3930 | DeclarationList Declaration
3932 Declaration -> ERROR Newlines ${
3934 "error: unhandled parse error", &$1);
3940 ## top level grammar
3942 ### The `const` section
3944 As well as being defined in with the code that uses them, constants
3945 can be declared at the top level. These have full-file scope, so they
3946 are always `InScope`. The value of a top level constant can be given
3947 as an expression, and this is evaluated immediately rather than in the
3948 later interpretation stage. Once we add functions to the language, we
3949 will need rules concern which, if any, can be used to define a top
3952 Constants are defined in a section that starts with the reserved word
3953 `const` and then has a block with a list of assignment statements.
3954 For syntactic consistency, these must use the double-colon syntax to
3955 make it clear that they are constants. Type can also be given: if
3956 not, the type will be determined during analysis, as with other
3959 As the types constants are inserted at the head of a list, printing
3960 them in the same order that they were read is not straight forward.
3961 We take a quadratic approach here and count the number of constants
3962 (variables of depth 0), then count down from there, each time
3963 searching through for the Nth constant for decreasing N.
3965 ###### top level grammar
3967 DeclareConstant -> const { IN OptNL ConstList OUT OptNL } Newlines
3968 | const { SimpleConstList } Newlines
3969 | const IN OptNL ConstList OUT Newlines
3970 | const SimpleConstList Newlines
3972 ConstList -> ConstList SimpleConstLine
3974 SimpleConstList -> SimpleConstList ; Const
3977 SimpleConstLine -> SimpleConstList Newlines
3978 | ERROR Newlines ${ tok_err(c, "Syntax error in constant", &$1); }$
3981 CType -> Type ${ $0 = $<1; }$
3984 Const -> IDENTIFIER :: CType = Expression ${ {
3988 v = var_decl(c, $1.txt);
3990 struct var *var = new_pos(var, $1);
3991 v->where_decl = var;
3996 v = var_ref(c, $1.txt);
3997 tok_err(c, "error: name already declared", &$1);
3998 type_err(c, "info: this is where '%v' was first declared",
3999 v->where_decl, NULL, 0, NULL);
4003 propagate_types($5, c, &ok, $3, 0);
4008 struct value res = interp_exec($5, &v->type);
4009 v->val = val_alloc(v->type, &res);
4013 ###### print const decls
4018 while (target != 0) {
4020 for (v = context.in_scope; v; v=v->in_scope)
4021 if (v->depth == 0) {
4032 printf(" %.*s :: ", v->name->name.len, v->name->name.txt);
4033 type_print(v->type, stdout);
4035 if (v->type == Tstr)
4037 print_value(v->type, v->val);
4038 if (v->type == Tstr)
4046 ### Finally the whole program.
4048 Somewhat reminiscent of Pascal a (current) Ocean program starts with
4049 the keyword "program" and a list of variable names which are assigned
4050 values from command line arguments. Following this is a `block` which
4051 is the code to execute. Unlike Pascal, constants and other
4052 declarations come *before* the program.
4054 As this is the top level, several things are handled a bit
4056 The whole program is not interpreted by `interp_exec` as that isn't
4057 passed the argument list which the program requires. Similarly type
4058 analysis is a bit more interesting at this level.
4063 ###### top level grammar
4065 DeclareProgram -> Program ${ {
4067 type_err(c, "Program defined a second time",
4074 Program -> program OpenScope Varlist ColonBlock Newlines ${
4077 $0->left = reorder_bilist($<Vl);
4079 var_block_close(c, CloseSequential);
4080 if (c->scope_stack && !c->parse_error) abort();
4083 Varlist -> Varlist ArgDecl ${
4092 ArgDecl -> IDENTIFIER ${ {
4093 struct variable *v = var_decl(c, $1.txt);
4100 ###### print binode cases
4102 do_indent(indent, "program");
4103 for (b2 = cast(binode, b->left); b2; b2 = cast(binode, b2->right)) {
4105 print_exec(b2->left, 0, 0);
4111 print_exec(b->right, indent+1, bracket);
4113 do_indent(indent, "}\n");
4116 ###### propagate binode cases
4117 case Program: abort(); // NOTEST
4119 ###### core functions
4121 static int analyse_prog(struct exec *prog, struct parse_context *c)
4123 struct binode *b = cast(binode, prog);
4130 propagate_types(b->right, c, &ok, Tnone, 0);
4135 for (b = cast(binode, b->left); b; b = cast(binode, b->right)) {
4136 struct var *v = cast(var, b->left);
4137 if (!v->var->type) {
4138 v->var->where_set = b;
4139 v->var->type = Tstr;
4143 b = cast(binode, prog);
4146 propagate_types(b->right, c, &ok, Tnone, 0);
4151 /* Make sure everything is still consistent */
4152 propagate_types(b->right, c, &ok, Tnone, 0);
4156 static void interp_prog(struct exec *prog, char **argv)
4158 struct binode *p = cast(binode, prog);
4165 al = cast(binode, p->left);
4167 struct var *v = cast(var, al->left);
4168 struct value *vl = v->var->val;
4170 if (argv[0] == NULL) {
4171 printf("Not enough args\n");
4174 al = cast(binode, al->right);
4176 free_value(v->var->type, vl);
4178 vl = val_alloc(v->var->type, NULL);
4181 free_value(v->var->type, vl);
4182 vl->str.len = strlen(argv[0]);
4183 vl->str.txt = malloc(vl->str.len);
4184 memcpy(vl->str.txt, argv[0], vl->str.len);
4187 v = interp_exec(p->right, &vtype);
4188 free_value(vtype, &v);
4191 ###### interp binode cases
4192 case Program: abort(); // NOTEST
4194 ## And now to test it out.
4196 Having a language requires having a "hello world" program. I'll
4197 provide a little more than that: a program that prints "Hello world"
4198 finds the GCD of two numbers, prints the first few elements of
4199 Fibonacci, performs a binary search for a number, and a few other
4200 things which will likely grow as the languages grows.
4202 ###### File: oceani.mk
4205 @echo "===== DEMO ====="
4206 ./oceani --section "demo: hello" oceani.mdc 55 33
4212 four ::= 2 + 2 ; five ::= 10/2
4213 const pie ::= "I like Pie";
4214 cake ::= "The cake is"
4223 print "Hello World, what lovely oceans you have!"
4224 print "Are there", five, "?"
4225 print pi, pie, "but", cake
4227 A := $Astr; B := $Bstr
4229 /* When a variable is defined in both branches of an 'if',
4230 * and used afterwards, the variables are merged.
4236 print "Is", A, "bigger than", B,"? ", bigger
4237 /* If a variable is not used after the 'if', no
4238 * merge happens, so types can be different
4241 double:string = "yes"
4242 print A, "is more than twice", B, "?", double
4245 print "double", B, "is", double
4250 if a > 0 and then b > 0:
4256 print "GCD of", A, "and", B,"is", a
4258 print a, "is not positive, cannot calculate GCD"
4260 print b, "is not positive, cannot calculate GCD"
4265 print "Fibonacci:", f1,f2,
4266 then togo = togo - 1
4274 /* Binary search... */
4279 mid := (lo + hi) / 2
4291 print "Yay, I found", target
4293 print "Closest I found was", mid
4298 // "middle square" PRNG. Not particularly good, but one my
4299 // Dad taught me - the first one I ever heard of.
4300 for i:=1; then i = i + 1; while i < size:
4301 n := list[i-1] * list[i-1]
4302 list[i] = (n / 100) % 10 000
4304 print "Before sort:",
4305 for i:=0; then i = i + 1; while i < size:
4309 for i := 1; then i=i+1; while i < size:
4310 for j:=i-1; then j=j-1; while j >= 0:
4311 if list[j] > list[j+1]:
4315 print " After sort:",
4316 for i:=0; then i = i + 1; while i < size:
4320 if 1 == 2 then print "yes"; else print "no"
4324 bob.alive = (bob.name == "Hello")
4325 print "bob", "is" if bob.alive else "isn't", "alive"