Re: [boost] Portable signbit macro/function?

From: Johan Råde (rade_at_[hidden])
Date: 2006-08-02 14:09:11

John Maddock wrote:
-Toolkit code, just a:
> 
> template <class T>
> int signbit(const T& v)
> { return v < 0 ? 1 : 0; }
> 
> To be honest that's not very useful :-(
> 
> What I do find more useful is:
> 
> template <class T>
> int sign(const T& v)
> { return v < 0 ? -1 : 1; }
> 
> which is invaluable when you need to compare the sign of two (or more) 
> numbers but are concerned about numeric overflow/underflow in the usual a*b 
> < 0 trick.
> 

Will not handle negative zero and negative NaN.
Will probably handle negative infinity.

--Johan