Implementation of Calculator using LEX and YACC

 Implementation of Calculator using LEX and YACC

Lex<Cal.L>

%{

#include"y.tab.h"

#include<math.h>

%}

%%

([0-9]+|([0-9]*\.[0-9]+)([eE][-+]?[0-9]+)?) {yylval.dval=atof(yytext);return

NUMBER;}

log |

LOG {return LOG;}

In {return nLOG;}

sin |

SIN {return SINE;}

cos |

COS {return COS;}

tan |

TAN {return TAN;}

mem {return MEM;}

[\t];

\$ return 0;

\n|. return yytext[0];

%%

Yacc<Cal.Y>

%{

double memvar;

%}

%union

{

double dval;

}

%token<dval>NUMBER

%token<dval>MEM

%token LOG SINE nLOG COS TAN

%left '-' '+'

%left '*' '/'

%right '^'

%left LOG SINE nLOG COS TAN

%nonassoc UMINUS

%type<dval>expression

%%

start:statement'\n'

|start statement'\n'

;

statement:MEM'='expression {memvar=$3;}

| expression{printf("Answer=%g\n",$1);}

;

expression:expression'+'expression {$$=$1+$3;}

| expression '-' expression {$$=$1-$3;}

| expression '*' expression {$$=$1*$3;}

| expression '/' expression

{ if($3==0)

yyerror("divide by zero");

else

$$=$1/$3;

}

|expression'^'expression {$$=pow($1,$3);}

;

expression:'-'expression %prec UMINUS{$$=-$2;}

|'('expression')'{$$=$2;}

|LOG expression {$$=log($2)/log(10);}

|nLOG expression {$$=log($2);}

|SINE expression {$$=sin($2*3.14/180);}

|COS expression {$$=cos($2*3.14/180);}

|TAN expression {$$=tan($2*3.14/180);}

|NUMBER {$$=$1;}

|MEM {$$=memvar;}

;

%%

main()

{

printf("Enter the expression");

yyparse();}

int yyerror(char *error)

{

printf("%s\n",error);

}