Re: [q-lang-users] Q 7.2 RC1 Issue 3: IEEE floats

[John C. <co...@cc...>]

Albert Graef scripsit:

> > But none of "on inf", "-inf", or "nan" has the correct meaning input.
> > This should be cleaned up.
> 
> I don't understand, what's "on inf"?

An editing blunder on my part: it should read:

> > But none of "inf", "-inf", or "nan" has the correct meaning on input.

> Defining inf and nan as const variables in the library would probably do 
> the trick. In fact, this is what I do (for inf) in some of my scripts.

Indeed.  You can define nan as inf - inf.

> > This should be cleaned up by defining a syntax for these values to
> > be used on input and output, and by not failing when doing a floating
> > division by zero (though an exact division by zero should still fail).
> 
> Is there a portable way to check for inf and nan values? (So that I 
> don't have to rely on the C library to do the right thing when printing 
> those numbers.)

int isinf(double f) {
        return (f + f == f);
        }

int isnan(double f) {
        return !(f == f);
        }

These depend on the "stickiness" of infinity and the fact that NaN
doesn't compare equal to anything, not even NaN.  (Do not simplify to
"f != f", as NaN doesn't compare *unequal* to anything either.)

-- 
Values of beeta will give rise to dom!          John Cowan
(5th/6th edition 'mv' said this if you tried    http://www.ccil.org/~cowan
to rename '.' or '..' entries; see              co...@cc...
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