init commit

1 files changed, 59 insertions, 0 deletions

diff --git a/lisp.y b/lisp.y
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+++ b/lisp.y
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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 sexprs
+
+%start sexprs
+
+%%
+opt_ws: /* matches no whitespace */
+      | WHITESPACE;
+
+sexprs: sexpr
+      | sexprs opt_ws sexpr;
+
+sexpr:  atom
+     |  LPAREN opt_ws sexpr opt_ws DOT opt_ws sexpr opt_ws RPAREN
+     {
+       $$ = cons($3, $7);
+       print_val($$);
+       printf("\n");
+     };
+
+atom:   NUMBER
+    {
+      if(is_integer($1)) {
+        $$ = make_int($1);
+      } else {
+        $$ = make_double($1);
+      }
+    }
+    |   LPAREN opt_ws RPAREN { $$ = make_nil(); }
+    |   STRING { $$ = make_string($1); };
+%%
+
+int yyerror(const char *s) { 
+  printf("%s\n",s); 
+}