Yacc program for a simple calculator

Author: root

scal.y

@@ -0,0 +1,87 @@
+%{
+/* Yacc program for a simple calculator */
+
+/*Header files*/
+#include<stdio.h>
+#include<stdlib.h>
+
+/*Function to calculate power*/
+double power(int a, int b);
+
+%}
+
+/*Union for YYSTYPE*/
+%union 
+{
+	int val;
+	
+};
+
+/*Tokens*/
+%token <val> NUMBER
+%token END
+
+/*Associativity*/
+%left '+' '-'
+%left '*' '/'
+%left '%'
+%nonassoc '^' 
+%nonassoc UMINUS
+
+/*Type of non-terminal*/
+%type <val> expr
+ 
+/*Start variable*/
+%start program
+
+%%
+
+program : expr END				{					
+							int ans = $1;
+							printf("\nResult : %d\n",ans);
+							exit(1);
+						}
+	;
+
+expr :   expr '+' expr				{$$=$1+$3;		}					
+	| expr '-' expr				{$$=$1-$3;		}
+	| expr '*' expr				{$$=$1*$3;		}
+	| expr '/' expr				{$$=$1/$3;		}
+	| expr '%' expr				{$$=$1%$3;		}
+	| '(' expr ')'				{$$=$2;			}
+	| '-' expr %prec UMINUS			{$$=-1*$2;		}
+	| expr '^' expr 			{$$=(int)power($1,$3);	}									
+	| NUMBER				{$$=$1;			}
+	;
+
+
+%%
+
+#include "lex.yy.c"
+
+double power(int a,int b)
+{
+	int i;
+	double c=1;	
+	for(i=0;i<b;i++)
+		c=c*a;
+	return c;
+}
+
+int yyerror(char *s)
+{
+	fprintf(stderr, "%s in line no : %d\n", s, yylineno);
+	return 1;
+}
+
+int yywrap(void)
+{
+	return 1;	
+}
+	
+int main()
+{
+	yyparse();
+	return 1;
+}
+