parse.y

   1 %{
   2 #include <stdio.h>
   3 #include <string.h>
   4 #include <stdlib.h>
   5
   6 #include "ast.h"
   7 #define YYSTYPE struct ast *
   8
   9 #include "y.tab.h"
  10
  11 int yylex(void);
  12
  13 void yyerror(struct ast **result, const char *str)
  14 {
  15         fprintf(stderr, "error: %s\n", str);
  16 }
  17
  18 int yywrap()
  19 {
  20         return 1;
  21 }
  22
  23 %}
  24
  25 %token INTEGER PLUS MINUS TIMES DIVIDE BOPEN BCLOSE SEMICOLON
  26 %parse-param { struct ast **result }
  27
  28 %%
  29
  30 start : exprs { *result = $1; } ;
  31
  32 exprs
  33         : { $$ = NULL; }
  34         | exprs expr SEMICOLON { $$ = ast_cons($2, $1); }
  35         ;
  36
  37 expr
  38         : expr PLUS fact { $$ = ast_binop($1, plus, $3); }
  39         | expr MINUS fact { $$ = ast_binop($1, minus, $3); }
  40         | fact
  41         ;
  42
  43 fact
  44         : fact TIMES basic { $$ = ast_binop($1, times, $3); }
  45         | fact DIVIDE basic { $$ = ast_binop($1, divide, $3); }
  46         | basic
  47         ;
  48
  49 basic
  50         : INTEGER
  51         | BOPEN expr BCLOSE { $$ = $2; }
  52         ;