Floating point - check for divide-by-zero

**pankaj401** · 03-13-2008

I need to know how could I check for a floating point number being "equal to" or "close enough" to 0.0f.
I have this:

Code:

buttonWidth = buttonRect.right - buttonRect.left;
buttonHeight = buttonRect.top - buttonRect.bottom;

// If button height or width is zero 
...

Would using

Code:

 buttonWidth > FLT_EPSILON

be okay?
Thanks

**whiteflags** · 03-13-2008

You can directly compare a floating point number with zero. That's one instance it's actually okay.

**matsp** · 03-13-2008

zero should be fine to compare with 0.0, as it's not going to give you a divide by zero exception for any number not matching exactly zero. [Although if you divide a large number by a very small number, e.g 1E300 / 1E-100, the result will be an overflow].

However, comparing to epsilon should be fine too.

--
Mats

**iMalc** · 03-13-2008

Originally Posted by citizen

You can directly compare a floating point number with zero. That's one instance it's actually okay.

I concur;
Especially if top, left bottom, and right are integer values.

**brewbuck** · 03-13-2008

if the quantity is not precisely zero, you won't get a divide by zero. Just check if it's zero.

**pankaj401** · 03-20-2008

Originally Posted by iMalc

I concur;
Especially if top, left bottom, and right are integer values.

All the variables involved are float.

I, finally, used the epsilon check.

**iMalc** · 03-20-2008

Originally Posted by pankaj401

All the variables involved are float.

I, finally, used the epsilon check.

Okay, so you ask for advice, and 4 people say to do one thing and you do the opposite. So why did you even bother to ask!?

**QuantumPete** · 03-20-2008

Originally Posted by iMalc

Okay, so you ask for advice, and 4 people say to do one thing and you do the opposite. So why did you even bother to ask!?

It's the right thing to do. Comparing to 0.0 *might* work, but it's not guaranteed. While not strictly necessary, a comparison to epsilon is always safe, so that should be the done thing. My advice on floats: don't use them!

QuantumPete

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