Thread: Very confused over floating points in if-statements

Thanks in advance for your time.

I was working with GLUT, and it was going well until for some inexplicable reason, my logic statement kept failing to... well, to be logical.

I rewrote it for all intents and purposes in a stripped-down program just to test the block itself (as below) and it ends up failing to test true ( x == 1.0f ) on the 10th iteration as it (I think?) should be doing.

I'd appreciate any insight on this, it's confused the heck out of me.

Code:

#include <iostream>
using namespace std;

int main( void )
{
	float x = 0.0f;
	for ( float c = 0.0; c < 1; c += 0.1f )
	{
		x += 0.1f;
		cout << "x is: " << x << endl;

                // This doesn't test true, even when x == 1
		if ( x == 1.0f )
			cout << "X hit the contingency.\n";
		else cout << "X has not yet hit.\n";
	}

	system("PAUSE");
	return 0;
}

If you have any thoughts, please don't hesitate to post them. Thanks again.

Well, try using double rather than float. Float is quite inaccurate. That can be the reason.

Double is twice as accurate as float is.

Ok. Thanks again to you both.

you could try:

Code:

for ( float c = 0.0; c != 1; c += 0.1f )

Some people recommend it.

JOKE! PLEASE DON'T CONTINUE THE DEBATE!