lambda.y

   1 %{
   2 #include "lambda.h"
   3 #include "lambda.tab.h"
   4 #include "mem.h"
   5
   6 struct lambda *result;
   7 struct decllist *decls = NULL;
   8 extern int yylex();
   9
  10 int yydebug=1;
  11 void yyerror(const char *str)
  12 {
  13         fprintf(stderr, "parse error: %s\n", str);
  14 }
  15
  16 int yywrap()
  17 {
  18         return 1;
  19 }
  20
  21 struct lambda *make_lambda()
  22 {
  23         return malloc(sizeof (struct lambda));
  24 }
  25
  26 struct lambda *make_ident(char *i)
  27 {
  28         struct lambda *r = make_lambda();
  29         r->which = lambda_ident;
  30         r->data.identifier = strdup(i);
  31         return r;
  32 }
  33
  34 struct lambda *make_abstraction(char *i, struct lambda *t)
  35 {
  36         struct lambda *r = make_lambda();
  37         r->which = lambda_abs;
  38         r->data.abstraction.ident = strdup(i);
  39         r->data.abstraction.expr = t;
  40         return r;
  41 }
  42
  43 struct lambda *make_application(struct lambda *t1, struct lambda *t2)
  44 {
  45         struct lambda *r = make_lambda();
  46         r->which = lambda_app;
  47         r->data.application.expr1 = t1;
  48         r->data.application.expr2 = t2;
  49         return r;
  50 }
  51
  52 void decls_prepend(char *ident, struct lambda *value)
  53 {
  54         struct decllist *head = malloc(sizeof (struct decllist));
  55         head->next = decls;
  56         head->ident = ident;
  57         head->value = value;
  58         decls = head;
  59 }
  60
  61 struct lambda *decls_lookup(char *ident)
  62 {
  63         struct decllist *c = decls;
  64         while(c != NULL){
  65                 if(strcmp(c->ident, ident) == 0)
  66                         return copy(c->value);
  67                 c = c->next;
  68         }
  69         return make_ident(ident);
  70 }
  71
  72 %}
  73
  74 %token LAMBDA DOT OBRACE CBRACE IDENT FUNC SEMICOLON ASSIGN
  75
  76 %%
  77
  78 lambda
  79         : decl lambda
  80         | term
  81                 { result = $$; }
  82 decl
  83         : FUNC ASSIGN term SEMICOLON
  84                 { decls_prepend($1->data.identifier, $3); }
  85 term
  86         : term appterm
  87                 { $$ = make_application($1, $2); }
  88         | appterm
  89                 { $$ = $1; }
  90 appterm
  91         : FUNC
  92                 {
  93                         $$ = decls_lookup($1->data.identifier);
  94                         lambda_free($1);
  95                 }
  96         | IDENT
  97                 {
  98                         $$ = make_ident($1->data.identifier);
  99                         lambda_free($1);
 100                 }
 101         | LAMBDA abstraction
 102                 { $$ = $2; }
 103         | OBRACE term CBRACE
 104                 { $$ = $2; }
 105 abstraction
 106         : IDENT abstraction
 107                 {
 108                         $$ = make_abstraction($1->data.identifier, $2);
 109                         lambda_free($1);
 110                 }
 111         | DOT term
 112                 { $$ = $2; }