Sela12 Sela12 - 4 days ago 4
C++ Question

A three numbers operation Calculator

The problem is that if the first action the program calculates (depends on the order of operation) is something divided by 0 (e.g 7/0+3, or 3+7/0), it prints the error message but performs the next action.

Example-

Input: 7/0+2 -----> Output: You can't divide by zero.7/0+2=2

What it should do ----> Output: You can't divide by zero.

It happens because I can't get it to skip the next switch action. If you have an idea or know how o fix it please help.
Thank you

P.S
If you know a better way to tackle the Order of Operation problem please help.

Shortened code:
Just enter something like 7+4/0 or 7-4/0

#include"stdafx.h"
using namespace System;
#include<iostream>
using namespace std;
int main()
{
long double num1, num2, num3, res;
char action1, action2;
cin >> num1 >> action1 >> num2 >> action2 >> num3;
if ((action2 == '*' || action2 == '/') && (action1 == '-' || action1 == '+')) //action2 will be preformed before action1 (Order of operation)
{
switch (action2) //I didn't include the options for '+' or '-' because the if statement requires action2 to be '*' or '/'.
{
case('/'):
if(num3==0)
cout<< "Error, you can't divide by zero";
else
res = num2 / num3;
break;
default:
cout << "Input not recognized";
break;
}
switch (action1)
{
case('+'):
cout << num1 << "+" << num2 << action2 << num3 << "=" << res + num1;
break;
case('-'):
cout << num1 << "-" << num2 << action2 << num3 << "=" << res - num1;
break;
default:
cout << "Input not recognized";
break;
}
}
cout << "\n\n";
system("PAUSE");
return 0;
}


Full code:

// Three numbers Calculator
/*Known problems: when the first action is divided by zero the programs prints the error message but runs the next action.
Other than that I think most of the stuff works but I need to check*/
#include "stdafx.h"
using namespace System;
#include<iostream>
using namespace std;
int main()
{
cout << "Enter action as # to exit program" << endl;
cout << "Possible actions:+,-,*,/\n" << endl;
int a = 1; //loop veriable
while (a == 1) //loop
{
long double num1, num2, num3, res;
char action1, action2;
cin >> num1 >> action1 >> num2 >> action2 >> num3;
if ((action2 == '*' || action2 == '/') && (action1 == '-' || action1 == '+')) //action2 will be preformed before action1 (Order of operation)
{
switch (action2) //I didn't include the options for '+' or '-' because the if statement requires action2 to be '*' or '/'.
{
case('/'):
if (num3 == 0) //The problem I described at the top occurs here and at another place below
cout << "You can't divide by zero.";
else
res = num2 / num3;
break;
case('*'):
res = num2*num3;
break;
default:
cout << "Input not recognized";
break;
}
switch (action1) //I didn't include the options for '*' or '/' because the if statement requires action1 to be '+' or '-'.
{
case('+'):
cout << num1 << "+" << num2 << action2 << num3 << "=" << res + num1;
break;
case('-'):
cout << num1 << "-" << num2 << action2 << num3 << "=" << res - num1;
break;
default:
cout << "Input not recognized";
break;
}
}
else //action1 will be performed before action2 (Order of operation)
{
switch (action1)
{
case('+'):
res = num1 + num2;
break;
case('-'):
res = num1 - num2;
break;
case('/'):
if (num2 == 0) //The problem I described at the top occurs here and at anothe place above
cout << "You can't divide by zero.";
else
res = num1 / num2;
break;
case('*'):
res = num1*num2;
break;
case('#'):
system("PAUSE");
return 0;
break;
default:
cout << "Input not recognized";
break;
}
switch (action2)
{
case('+'):
cout << num1 << action1 << num2 << "+" << num3 << "=" << res + num3;
break;
case('-'):
cout << num1 << action1 << num2 << "-" << num3 << "=" << res - num3;
break;
case('/'):
if (num3 == 0)
cout << "You can't divide by zero.";
else
res = num2 / num3;
break;
case('*'):
res = num2*num3;
break;
case('#'):
system("PAUSE");
return 0;
break;
default:
cout << "Input not recognized";
break;
}
}
cout << "\n\n";
}
}

Answer

Have a special check for division by zero right after the input (and before the if) and if so just continue the loop.

So something like

while (...)
{
    ...
    std::cin >> ...
    if (action1 == '/' && num2 == 0 || action2 == '/' && num3 == 0)
    {
        std::cout << "Division by zero\n";
        continue;
    }
    if (...)
    ...
}
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