Re: [Gretl-devel] msortby() stumbles over NA / nan

On Wed, 3 Dec 2014, Sven Schreiber wrote: > Am 03.12.2014 um 16:59 schrieb Allin Cottrell: > >> >> It's more complicated than that, and msortby is actually not doing >> anything odd. What's odd, I gather, is the behavior of the Microsoft C >> library in the cases you said came out "OK". > > How can I test the C library behavior? Maybe a simple C code snippet -- > but compiling on a non-dev Windows machine is tricky I guess? I tried a little test program on Windows 8. It turns out that the C library does return 0 for all comparisons involving a NaN (>, < and ==), as it should. Nonetheless, qsort() with our original simple callback sorts NaN (invoked via 0.0/0.0) to the start of an array of doubles. I don't know how that happens!