Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people, just like you, are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
Solved

testing for infinity

Posted on 2000-03-14
3
663 Views
Last Modified: 2008-03-17
How do I check to see whether a number has gone out of range?  The check for positive infinity works, but the following doesn't:

float x=1.0;
if (x == numeric_limits<float>::quiet_NaN())
{
  do something
}

What happens is that the comparison always comes up true.

What's the trick to doing this check?
0
Comment
Question by:Ashurbanipal
  • 2
3 Comments
 
LVL 22

Accepted Solution

by:
nietod earned 50 total points
ID: 2617422
You don't want to compare with quiet_Nan().  

Use max() instead.  Positive infinity is the only number greater than max(), like

if (x == numeric_limits<float>::max())
0
 

Author Comment

by:Ashurbanipal
ID: 2618308
if (x == numeric_limits<float>::infinity())

seems to work, but

if (x == numeric_limits<float>::max())

generates a compiler error that says max() needs parameters.

Is there any reason not to use infinity()?
0
 
LVL 22

Expert Comment

by:nietod
ID: 2619410
>> Is there any reason not to use infinity()?
Probably not. I simply didn't realize it was there.

>> if (x == numeric_limits<float>::max())
>> generates a compiler error that says max() needs parameters
numeric_limits::max()  does not require any parameters.  (And the code I suggested works, I did test it, because I had never tried that with floating point before.)

I suspect that the problem may be that you have the C (not C++) max() function #defined in your program so the preprocessor is converting the max() if finds to the code of the max function.
0

Featured Post

Announcing the Most Valuable Experts of 2016

MVEs are more concerned with the satisfaction of those they help than with the considerable points they can earn. They are the types of people you feel privileged to call colleagues. Join us in honoring this amazing group of Experts.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
MSVCR80.dll crash 2 141
Handle Exceptions during instantiation 28 422
Problem with SqlConnection 4 176
How to Correctly derive class from CWinThread in MFC 4 64
IntroductionThis article is the second in a three part article series on the Visual Studio 2008 Debugger.  It provides tips in setting and using breakpoints. If not familiar with this debugger, you can find a basic introduction in the EE article loc…
This article shows you how to optimize memory allocations in C++ using placement new. Applicable especially to usecases dealing with creation of large number of objects. A brief on problem: Lets take example problem for simplicity: - I have a G…
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…
The viewer will be introduced to the technique of using vectors in C++. The video will cover how to define a vector, store values in the vector and retrieve data from the values stored in the vector.

792 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question