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From: John Maddock (john_at_[hidden])
Date: 2008-02-27 11:31:46

Johan Råde wrote:
>> There is one other useful function worth having IMO:
>> template <class T>
>> int sign(T x);
>> returns 0 (x is zero), +1 (x is > 0) or -1 (x is < 0). This is
>> trivial to implement (lot's of old C code - for example the
>> Numerical Recipies stuff - implement this as a helper macro), and
>> there's an undocumented version currently in Boost.Math. Is this
>> worth integrating with Johan's code? I've found it quite useful in
>> Boost.Math from time to time.
> What should this function return for a NaN?

In any of the use cases I have for that function, it would be an error to be
trying to handle NaN's. So it's a domain error I guess.


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