Question

I was struck by this strange behavior:

float pi = 3.14;

if(pi == 3.14)
    cout << "OK";
else
    cout << "How is it possible?";

Could anyone explain this?

Answer 1

The constant in the if statement is (double)3.14. It is very close to its float version, but not exactly equals it, because 3.14 is not represented exactly.

Try the same trick with 1.25 or any other number that can be represented exactly, and you will get an OK.

float num = 1.25;
if(num == 1.25)
    cout << "OK";
else
    cout << "How is it possible?";

You could also cast 3.14 to float to get an OK:

float pi = 3.14;

if(pi == (float)3.14)
    cout << "OK";
else
    cout << "How is it possible?";