Justin, > > What man page is this intended for? > qsort() > > > > Included is a sample program that demonstrates how to sort IEEE > > > floating point values, including NAN and friends, in a useful way; > > > please consider including it. > > > > > > // make CFLAGS='-W -Wall -O3 -g -std=gnu99' LDFLAGS=-lm fpnansort > > > #include <math.h> > > > #include <stdlib.h> > > > #include <stdio.h> > > > #include <assert.h> > > > > > > int fpcomp(const void *a, const void *b) > > > { > > > double x=*(double *)a, > > > y=*(double *)b; > > > > > > if (x<y) return -1; > > > else if (x>y) return 1; > > > // The not-normal values will be grouped together, but > > > // otherwise unordered: > > > else if (!isnormal(x)) return 1; > > > else if (!isnormal(y)) return -1; > > > > Why isnormal()? > "Why not" ? > > Seriously, I want all the IEEE special number foo to get out of my > way, and this does wha tI want.
Do you realise that "!isnormal(0.0) == 1"? What happens when you compare 0.0 with 0.0? > > > assert(x==y); > > > > What is assert doing here? > Well, the current qsort() example uses assert() on argc, so why not? The context is different: one kills the program because it got bad arguments. The other kills the quicksort because the comparison function encountered a case that it didn't expect. It just looks a bit strange is all. > Seriously, I *think* that x==y is guaranteed, since x and y are both > "normal" values, but there might be other special cases of which I'm > not even aware; this is as way of checking for them, and at the same > time indicating my intent. (Actually, "subnormal" may just be that > case .. will think about it.) I'm *not at all* convinced that including an example like this is appropriate for the qsort man page: it isn't the place to teach about floating point numbers. Cheers, Michael -- Michael Kerrisk maintainer of Linux man pages Sections 2, 3, 4, 5, and 7 Want to help with man page maintenance? Grab the latest tarball at ftp://ftp.win.tue.nl/pub/linux-local/manpages/, read the HOWTOHELP file and grep the source files for 'FIXME'. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]