#include <iostream>
using namespace std;
int main()
{
char s[80];
cout << "Please enter expression : " << endl;
cin >> s;
char op = 0;
int i, x = 0, y = 0, err = 0;
for (i = 0; s[i]; i++);
s[i] = '=';
s[i + 1] = 0;
for (i = 0; (s[i]) && (err == 0); i++)
{
switch (s[i])
{
case ' ' :
break;
case '+' :
case '-' :
case '*' :
case '/' :
case '=' :
switch (op)
{
case 0 :
x = y;
break;
case '+' :
x += y;
break;
case '-' :
x -= y;
break;
case '*' :
x *= y;
break;
case '/' :
if (y == 0)
{
cout << endl << "Divide by zero." << endl;
err = 1;
}
else
x /= y;
}
y = 0;
op = s[i];
break;
default :
if ((s[i] >= '0') && (s[i] <= '9'))
y = y * 10 + s[i] - '0';
else
{
cout << endl << "Invalid character '" << s[i] << "'." << endl;
err = 1;
}
}
}
if (err == 0)
cout << endl << "result = " << x << endl;
return 0;
}
