[Numpy-discussion] isinf raises in inf

[Pauli Virtanen]

Thu, 15 Jul 2010 19:09:15 -0600, Charles R Harris wrote:
[clip]
> PS, of course we should fix the macro also. Since the bit values of +/-
> infinity are known we should be able to define them as constants using a
> couple of ifdefs and unions.

We already do that, NPY_INFINITY and -NPY_INFINITY.

[clip]
> int
> (isinf)(double x)
> {
>     if ((-1.0 < x) && (x < 1.0))    /* x is small, and thus finite */
>     return (0);
>     else if ((x + x) == x)        /* only true if x == Infinity */
>     return (1);
>     else              /* must be finite (normal or subnormal), or NaN */
>     return (0);
> }

This function can generate overflows, for example for

	x = 0.6 * np.finfo(np.float64).max

-- 
Pauli Virtanen