lambda.y

   1 %{
   2 #include "lambda.h"
   3 #include "lambda.tab.h"
   4 #include "mem.h"
   5 #include "print.h"
   6
   7 struct lambda *result;
   8 struct decllist *decls = NULL;
   9 extern int yylex();
  10
  11 int yydebug=1;
  12 void yyerror(const char *str)
  13 {
  14         fprintf(stderr, "parse error: %s\n", str);
  15 }
  16
  17 int yywrap()
  18 {
  19         return 1;
  20 }
  21
  22 struct lambda *make_lambda()
  23 {
  24         return malloc(sizeof (struct lambda));
  25 }
  26
  27 struct lambda *make_ident(char *i)
  28 {
  29         struct lambda *r = make_lambda();
  30         r->which = lambda_ident;
  31         r->data.identifier = strdup(i);
  32         return r;
  33 }
  34
  35 struct lambda *make_abstraction(char *i, struct lambda *t)
  36 {
  37         struct lambda *r = make_lambda();
  38         r->which = lambda_abs;
  39         r->data.abstraction.ident = strdup(i);
  40         r->data.abstraction.expr = t;
  41         return r;
  42 }
  43
  44 struct lambda *make_application(struct lambda *t1, struct lambda *t2)
  45 {
  46         struct lambda *r = make_lambda();
  47         r->which = lambda_app;
  48         r->data.application.expr1 = t1;
  49         r->data.application.expr2 = t2;
  50         return r;
  51 }
  52
  53 void decls_prepend(char *ident, struct lambda *value)
  54 {
  55         struct decllist *head = malloc(sizeof (struct decllist));
  56         head->next = decls;
  57         head->ident = ident;
  58         head->value = value;
  59         printf("Declared %s as ", ident);
  60         lambda_print(value);
  61         decls = head;
  62 }
  63
  64 struct lambda *decls_lookup(char *ident)
  65 {
  66         struct decllist *c = decls;
  67         while(c != NULL){
  68                 if(strcmp(c->ident, ident) == 0)
  69                         return copy(c->value);
  70                 c = c->next;
  71         }
  72         return make_ident(ident);
  73 }
  74
  75 %}
  76
  77 %token LAMBDA DOT OBRACE CBRACE IDENT FUNC SEMICOLON ASSIGN
  78
  79 %%
  80
  81 lambda
  82         : decl lambda
  83         | term
  84                 { result = $$; }
  85 decl
  86         : FUNC ASSIGN term SEMICOLON
  87                 { decls_prepend($1->data.identifier, $3); }
  88 term
  89         : term appterm
  90                 { $$ = make_application($1, $2); }
  91         | appterm
  92                 { $$ = $1; }
  93 appterm
  94         : FUNC
  95                 {
  96                         $$ = decls_lookup($1->data.identifier);
  97                         lambda_free($1);
  98                 }
  99         | IDENT
 100                 {
 101                         $$ = make_ident($1->data.identifier);
 102                         lambda_free($1);
 103                 }
 104         | LAMBDA abstraction
 105                 { $$ = $2; }
 106         | OBRACE term CBRACE
 107                 { $$ = $2; }
 108 abstraction
 109         : IDENT abstraction
 110                 {
 111                         $$ = make_abstraction($1->data.identifier, $2);
 112                         lambda_free($1);
 113                 }
 114         | DOT term
 115                 { $$ = $2; }