plzzz help…….it doesn’t evaluate right……!

[WeldonGarrison]

#include <stdio.h>
#include <ctype.h>

#define MAX 50
#define EMPTY -1

struct stack
{
int data[MAX];
int top;
};

int isempty(struct stack *s)
{
return (s->top == EMPTY) ? 1 : 0;
}

void emptystack(struct stack* s)
{
s->top = EMPTY;
}

void push(struct stack* s,int item)
{
if(s->top == (MAX-1))
{
printf("nSTACK FULL");
}
else
{
++s->top;
s->data[s->top]=item;
}
}

int pop(struct stack* s)
{
int ret=EMPTY;
if(s->top == EMPTY)
printf("nSTACK EMPTY");
else
{
ret= s->data[s->top];
--s->top;
}
return ret;
}

void display(struct stack s)
{
while(s.top != EMPTY)
{
printf("n%d",s.data[s.top]);
s.top--;
}
}

int isoperator(char e)
{
if(e == '+' || e == '-' || e == '*' || e == '/' || e == '%')
return 1;
else
return 0;
}

int priority(char e)
{
int pri = 0;

if(e == '*' || e == '/' || e =='%')
pri = 2;
else
{
if(e == '+' || e == '-')
pri = 1;
}
return pri;
}

int evaluate(char *postfix)
{
char *p;
struct stack stk;
int op1,op2,result;

emptystack(&stk);
p = &postfix[0];

while(*p != '')
{
/* removes tabs and spaces */
while(*p == ' ' || *p == 't')
{
p++;
}
/* if is digit */
if(isdigit(*p))
{
push(&stk,*p - 48);
}
else
{
/* it is an operator */
op2 = pop(&stk);
op1 = pop(&stk);

switch(*p)
{
case '+':
result = op1 + op2;
break;

case '-':
result = op1 - op2;
break;

case '/':
result = op1 / op2;
break;

case '*':
result = op1 * op2;
break;

case '%':
result = op1 % op2;
break;

default:
printf("nInvalid Operator");
return 0;
}
push(&stk,result);
}
p++;
}
result = pop(&stk);
return result;
}

void infix2postfix(char* infix, char * postfix, int insertspace)
{
char *i,*p;
struct stack X;
char n1;
emptystack(&X);
i = &infix[0];
p = &postfix[0];

while(*i)
{
while(*i == ' ' || *i == 't')
{
i++;
}

if( isdigit(*i) || isalpha(*i) )
{
while( isdigit(*i) || isalpha(*i))
{
*p = *i;
p++;
i++;
}
/*SPACE CODE*/
if(insertspace)
{
*p = ' ';
p++;
}
/*END SPACE CODE*/
}

if( *i == '(' )
{
push(&X,*i);
i++;
}

if( *i == ')')
{
n1 = pop(&X);
while( n1 != '(' )
{
*p = n1;
p++;
/*SPACE CODE*/
if(insertspace)
{
*p = ' ';
p++;
}
/*END SPACE CODE*/
n1 = pop(&X);
}
i++;
}

if( isoperator(*i) )
{
if(isempty(&X))
push(&X,*i);
else
{
n1 = pop(&X);
while(priority(n1) >= priority(*i))
{
*p = n1;
p++;
/*SPACE CODE*/
if(insertspace)
{
*p = ' ';
p++;
}
/*END SPACE CODE*/
n1 = pop(&X);
}
push(&X,n1);
push(&X,*i);
}
i++;
}
}
while(!isempty(&X))
{
n1 = pop(&X);
*p = n1;
p++;
/*SPACE CODE*/
if(insertspace)
{
*p = ' ';
p++;
}
/*END SPACE CODE*/
}
*p = '';
}

int main(void)
{
char infix[MAX], postfix[MAX], result[MAX];
printf("Enter expression: ");
fflush(stdin);
gets(infix);
infix2postfix(&infix[0],&postfix[0],1);
printf("nPostfix expression is: %s",&postfix[0]);
result[0]=postfix[0];
printf("n %s = %d.",&infix[0],evaluate(&result[0]));
return 0;
}

• This topic was modified 1 year, 10 months ago by M. Saqib.
• This topic was modified 1 year, 10 months ago by M. Saqib.

[GWILouisaxwzkla]

Heres a postfix to infix program I have on my drive ( hope this helps….. ):

#include < conio.h >

#include < math.h >

#include < string.h >

#include < stdlib.h >

#include < stdio.h >



enum Boolean { False = 0 , True = 1 } ;

const int GREATER = 1 ;

const int NOTGREATER = 0 ;

int cnt = 0 , cntcol = 0 , postcnt = 0 ;



//

struct Stack

{

int info ;

Stack * previous;

} * top;



//

void Push ( int number )

{

Stack * current;

current = new ( Stack ) ;

if ( current == 0 )

{

printf ( "n allocation error!!!!! " );

return;

}

current -> info = number ;

current -> previous = top ;

top = current ;

}



//

int Pop ()

{

int temp ;

Stack * current = top;

temp = current -> info ;

top = top -> previous ;

delete current ;

return temp ;

}



//

int StackTop ()

{

return top -> info ;

}



//

Boolean isEmpty()

{

if ( top == NULL )

return True;

else

return False ;

}



//

Boolean isOperand ( char ch )

{

if ( ch >= '0' && ch <= '9' ) //if is a number

return True;

else

return False ;

}



//

void Infix ( char infix[][10])

{

char c ;

while ( c != 13 )

{

c = getch() ;

putch(c);

if ( c >= '0' && c <= '9' )

{

infix [cnt][cntcol] = c  ;

cntcol++ ;

}

else if ( c == '+'|| c == '-'|| c == '*'|| c == '/')

{

infix [cnt][cntcol] = '' ;

cnt++ ;

infix [cnt][0] = c ;

infix [cnt][1] = '' ;

cnt++ ;

cntcol = 0 ;

}

else if ( c == 13 )

infix[cnt][cntcol] = '' ;

}

}





//

int Calculate (int op1, char opr, int op2)

{

int ans ;

switch ( opr )

{

case '+' :  ans = op1 + op2 ; break ;

case '-' :  ans = op1 - op2 ; break ;

case '*' :  ans = op1 * op2 ; break ;

case '/' :  ans = op1 / op2 ; break ;

case '^' :  ans = pow(op1, op2) ;

}

return ans ;

}

//

int Evaluate ( char postfix[][10] )

{

for ( int i = 0 ; i <= cnt ; i ++ )

{

char ch = postfix[0] ;

char ch1[10] ;

strcpy ( ch1 ,postfix  ) ;

//  cout <
if ( isOperand ( ch ) == True )

Push ( atoi(ch1)  );

else

{

int op2 = Pop () ;

int op1 = Pop () ;

int ans = Calculate ( op1, ch, op2 ) ;

//	    cout << ans << endl ;

Push ( ans ) ;

}

}

int ans = Pop () ;

return ans ;

}



// 

int CheckP (char cur, char st)

{

int a = NOTGREATER ;



if ( cur == '(' )

a = GREATER ;

else if ( cur != '(' && st == '(' )

a = GREATER ;

else if ( cur != '(' && st != '(' )

{

if ( ( cur == '*' || cur == '/' ) && ( st == '+' || st == '-' ) )

a = GREATER ;

}

return a ;



}





//

void infixToPostfix ( char infix[][10], char postfix[][10] )

{

int postcol = 0 ;

for ( int i = 0 ; i <= cnt ; i ++ )

{

//	strcpy(postfix, infix ) ;

//		cout << postfix ;

char ch;

ch = infix[0]  ;

if ( isOperand ( ch ) == True )

strcpy ( postfix [postcnt++] , infix  ) ;

else

{

if ( isEmpty() == True )

Push ( int(ch) ) ;

else

{

while ( CheckP( ch, StackTop() ) != GREATER && isEmpty() != True )

{

char c ;

if ( ch == ')' )

{

do

{

c = char ( Pop() ) ;

if ( c != '(')

{

postfix [postcnt][postcol] = c ;

postfix [postcnt][postcol+1] = '' ;

postcnt++ ;

}

}while ( c != '(' && isEmpty() != True);

break ;

}

else

c = char ( Pop() ) ;

if ( c != '(' && c != ')' )

{

postfix [postcnt][postcol] = c ;

postfix [postcnt][postcol+1] = '' ;

postcnt++ ;

}

}

if ( ch != ')' )

Push ( int(ch) ) ;

}

}

}



while ( isEmpty () != True )

{

char c = char ( Pop () ) ;

postfix [postcnt][postcol] = c ;

postfix [postcnt][postcol+1] = '';

postcnt++ ;

}

//   postfix[postcnt][postcol]  = '';

}



//

void Postfix ( char postfix[][10] )

{

char ch[10] ;

for ( int i = 0; i <= postcnt; i++ )

{

strcpy(ch , postfix ) ;

printf ( "%c" ,ch );

}

}



// 

void main()

{

//clrscr();

top = NULL ;



char infix [ 50 ][ 10 ] ;

char postfix [ 50 ][ 10 ] ;



//gotoxy ( 5, 8 ) ;

printf ( "Enter Arithematic Expression ...................... : " );

Infix ( infix ) ;



infixToPostfix ( infix, postfix ) ;

//gotoxy ( 5, 10 ) ;

printf ( "Arithematic Expression in Postfix Notation......... : " );

Postfix ( postfix ) ;

int ans = Evaluate ( postfix ) ;

//gotoxy (5, 11 ) ;

printf (  "The Answer of Expression .......................... : " );

printf ( "%i", ans );



getch();

}

//

[PSBMaira490593]

Hi,
please run it again in new window and check the variable that you have declared are right or not.
thanks.

---

Debra Fine

[M. Saqib]

OK

[Author]

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