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|
%{
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "lisp.h"
int yylex(void);
int yyerror(const char *s);
static int is_integer(double x) {
return floor(x) == x && isfinite(x);
}
%}
%union {
int ival;
double dval;
const char *strval;
value *val;
}
%token <dval> NUMBER
%token <strval> STRING
%token <ival> LPAREN RPAREN DOT WHITESPACE
%token <ival> PLUS MINUS MULT DIV
%type <val> sexpr atom list list_items
%start sexprs
%%
opt_ws: /* matches no whitespace */
| WHITESPACE;
sexprs: sexpr { print_val($1); printf("\n"); }
| sexprs opt_ws sexpr { print_val($3); printf("\n"); };
sexpr: atom
| list
| LPAREN opt_ws sexpr opt_ws DOT opt_ws sexpr opt_ws RPAREN
{
$$ = cons($3, $7);
print_val($$);
printf("\n");
};
list: LPAREN opt_ws list_items opt_ws RPAREN
{ $$ = $3; };
list_items: /* empty list */ { $$ = make_nil(); }
| sexpr opt_ws list_items { $$ = cons($1, $3); }
| sexpr WHITESPACE DOT WHITESPACE sexpr { $$ = cons($1, $5); };
atom: NUMBER
{
if(is_integer($1)) {
$$ = make_int($1);
} else {
$$ = make_double($1);
}
}
| STRING { $$ = make_string($1); };
%%
int yyerror(const char *s) {
printf("%s\n",s);
}
|
