IMPLEMENTATION OF CALCULATOR USING LEX AND YACC

				
					Lex
%{
#include"y.tab.h"
#include
%}
%%
([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
%{
double memvar;
%}
%union
{
double dval;
}
%tokenNUMBER
%tokenMEM
%token LOG SINE nLOG COS TAN
%left '-' '+'
%left '*' '/'
%right '^'
%left LOG SINE nLOG COS TAN
%nonassoc UMINUS
%typeexpression
%%
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);
}
				
			
OUTPUT:
[linuxpert@fosslab ~]$ vi cal.l
[linuxpert@fosslab ~]$ lex cal.l
[linuxpert@fosslab ~]$ yacc -d cal.y
[linuxpert@fosslab ~]$ cc lex.yy.c y.tab.c -ll -lm
[linuxpert@fosslab ~]$ ./a.out
Enter the expression(5+2)*(3-1)/(2)
Answer=7
 

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