Binary Calculator

Using lex-yacc implement bc like application of unix.

YACC FILE

Source Code:
%{
#include 
#include
int yylex(void);
void yyerror(char *);
int s[26];
%}
%token INTEGER VAR S
%left '+' '-'
%left '*' '/'
%%
program	:program stmt '\n'
	|
	;
stmt	:e		{ printf("%d\n", $1); }
	|VAR '=' e	{ s[$1]=$3;}
	;

e	:e '+' t	{ $$=$1 + $3;}
	|e '-' t	{ $$=$1 - $3;}
	|t		{$$=$1;}
	;

t	:t '*' f	{ $$=$1 * $3;}
	|t '/' f	{ $$=$1 / $3;}
	|f		{ $$=$1;}
	;
f	: '(' e ')'	{ $$=$2;}
	|INTEGER	{ $$=$1;}
	|VAR		{$$=s[$1];}
	|S '(' INTEGER ')' {$$=sqrt($3);}
	;

	


%%
void yyerror(char *s)
 {
fprintf(stderr, "%s\n", s);
}

int main(void) {
yyparse();
return 0;
}




Lex FILE

Source Code:
%{
#include 
void yyerror(char *);
#include "y.tab.h"
%}
%%
"sqrt"	{return S;}
[0-9]+	{yylval = atoi(yytext);return INTEGER;}
[a-z]	{yylval=*yytext-'a';return VAR;}
[-+*/()=\n] 	return *yytext;
[ \t] 	; /* skip whitespace */
. 	yyerror("invalid character");
%%
int yywrap(void) {
return 1;
}


OUTPUT:

[cmsa2@localhost ~]$ yacc -d calculator.y
[cmsa2@localhost ~]$ lex calculator.l
[cmsa2@localhost ~]$ cc lex.yy.c y.tab.c -lm -o cal
[cmsa2@localhost ~]$ ./cal
a=5
b=sqrt(49)
c=(a*b)-4
c
31