compare on Double

[Ketil Malde]

Neil Mitchell wrote:
> I'm still not happy with adding more incompleteness into something
> that intuitively feels safe - compare is pretty benign. Having a crash
> on division is something that does appeal to me more.
Are you suggesting that 0.0/0.0 should crash also?  I'm no expert, but 
think returning a NaN is according to the floating point standard (IEEE 
754), and I'm not convinced Haskell should break that.  If you use 
floating point, you need to know the pitfalls anyway.  Maybe comparing 
NaNs should give random results? :-)

The bad thing is that comparison can hide the NaNs (for arithmetic, NaNs 
will be contagious, so you'll likely get a NaN riddled output).  One 
thing I remember seeing (from Fortran compilers?) is that when a program 
execution involves a NaN, it is reported on termination, even if the NaN 
was in an intermediate calculation and not part of the final result.  
Something like that could perhaps be useful if the current behavior is kept?

-k