Can someone tell me what's wrong with my C++ code (I'm very new to coding)

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#include <iostream>
using namespace std;

int
main ()
{
  int x, y, z;
  int sum;
  cout << "1 = add, 2 = subtract, 3 = multiply 4 = divide: ";
  cin >> z;
  cout << "Type a number: ";
  cin >> x;
  cout << "Type a second number: ";
  cin >> y;
  if (z = 1)
    sum = x + y;
  if (z = 2)
    sum = x - y;
  if (z = 3)
    sum = x * y;
  if (z = 4)
    sum = x / y;
  cout << "answer is: " << sum;
  return 0;
}

It keeps just trying to divide everything instead of anything else and I don't know what the problem is.

What I have tried:

It started when I got a suggestion from a friend to change sum to answer (it was originally just for adding bc I didn't know how to use everything else yet). I did it and it stoped working so I put it back to normal but it still wasn't working.

Posted 10-Mar-23 8:52am

Conner Mason

Updated 10-Mar-23 10:04am

jeron1

v2

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jeron1 10-Mar-23 15:47pm

The comparison operator used in the if statement should be == not =. The single equal sign is an assignment operator, which is setting the z variable to whatever is after the equals sign. Also, the result of the division is going to be an integer (no fraction), perhaps not what you wanted.

OriginalGriff 11-Mar-23 1:43am

Answer updated.

2 solutions

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Patrice T · Answer 1 · 2023-03-10T09:42:00

Solution 1

Ton compare z with 1, need to replace

C++

if (z = 1)

with

C++

if (z == 1)

Posted 10-Mar-23 9:42am

Patrice T

OriginalGriff · Answer 2 · 2023-03-10T10:04:00

To add to what Patrice has said, "=" is an assignment operator: The value on the right hand side is "put into" the variable on the left. "==" is a comparison operator which returns either 0 or 1 depending on the two values.
If they re the same, it returns 0. If not, it returns 1.

But C++ is based on the much older language C where 0 means "false" and any non-zero value means "true" - and an assignment operator returns the value that it set, so you can "chain" them:

C++

a = b = c = 666;

assigns the value 666 to c, then returns 666 which is then assigned to b, which returns 666 to be assigned to a.
So when you write

if (z = 1)

the value of z is overwritten with 1 and 1 is returned to be used as the comparison - and since it's non-zero it is always true.
And the same thing happens with the next comparison!

I'd also suggest that you look at either

if (z == 1)
   ...
else if (z == 2)
   ...
else if (z == 3)
   ...
else if (z == 4)
   ...
else
   ... tell him you don't understand ...

or better, use a switch block.