neethiventhan123 / ex-11-implementation-of-calculator-using-lex-and-yacc-

IMPLEMENTATION OF CALCULATOR USING LEX AND YACC

Ex-11-IMPLEMENTATION-OF-CALCULATOR-USING-LEX-AND-YACC-

IMPLEMENTATION OF CALCULATOR USING LEX AND YACC

Aim :

To implement a calculator using LEX and YACC.

ALGORITHM

1. Start the program.
2. Write a program in the vi editor and save it with .l extension.
3. In the lex program, write the translation rules for the various mathematical functions.
4. Write a program in the vi editor and save it with .y extension.
5. Compile the lex program with lex compiler to produce output file as lex.yy.c. eg $ lex filename.l
6. Compile the yacc program with yacc compiler to produce output file as y.tab.c. eg $ yacc –d arith_id.y
7. Compile these with the C compiler as gcc lex.yy.c y.tab.c
8. Enter an expression as input and it is evaluated and the answer is displayed as output.

PROGRAM

Program: calculator.l file

%{
#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;}
ln |
LN {return nLOG;}
sin |
SIN {return SINE;}
cos |
COS {return COS;}
tan |
TAN {return TAN;}
mem {return MEM;}
[\t];
\$ return 0;
\n|. return yytext[0];
%%

Program: calculator.y file

%{
double memvar;
%}

%union { double dval; }

%token <dval> NUMBER
%token <dval> MEM
%token LOG nLOG SINE COS TAN
%left '-' '+'
%left '*' '/'
%right '^'
%left LOG nLOG SINE 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; }
;

%%

int main() {
printf("Enter the expression: ");
yyparse();
return 0;
}

int yyerror(char *error) {
printf("%s\n", error);
return 0;
}

OUTPUT

RESULT

The calculator is implemented using LEX and YACC and the output is verified.