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

Am 04.12.2014 um 21:27 schrieb Allin Cottrell: > On Thu, 4 Dec 2014, Sven Schreiber wrote: > >>> >>> 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! >> >> sorry for being clueless, but what is qsort() -- gretl's internal call >> to a quicksort algorithm perhaps? > > qsort is the standard C library quicksort function (defined in > stdlib.h). Gretl calls it for sorting -- we haven't felt a need for > our own quicksort implementation. But to use qsort you need to supply > your own comparison function for the objects you're sorting (what I'm > calling the "callback"). Ok, anything I could do to investigate this issue further?