Date: Wed, 20 Feb 2013 00:25:24 -0800 From: mdf@FreeBSD.org To: Giorgos Keramidas <keramida@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r247014 - head/lib/libc/stdlib Message-ID: <CAMBSHm-ZPNAYj1tqs%2B8paYJgn69=zPe5O-tsn1dvn4t2156muA@mail.gmail.com> In-Reply-To: <201302192357.r1JNveLq039940@svn.freebsd.org> References: <201302192357.r1JNveLq039940@svn.freebsd.org>
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On Tue, Feb 19, 2013 at 3:57 PM, Giorgos Keramidas <keramida@freebsd.org> wrote: > Author: keramida (doc committer) > Date: Tue Feb 19 23:57:39 2013 > New Revision: 247014 > URL: http://svnweb.freebsd.org/changeset/base/247014 > > Log: > Add a sample program that shows how a custom comparison function and > qsort(3) can work together to sort an array of integers. > > PR: docs/176197 > Submitted by: Fernando, fapesteguia at opensistemas.com > Approved by: gjb (mentor) > MFC after: 1 week > > Modified: > head/lib/libc/stdlib/qsort.3 > > Modified: head/lib/libc/stdlib/qsort.3 > ============================================================================== > --- head/lib/libc/stdlib/qsort.3 Tue Feb 19 23:46:51 2013 (r247013) > +++ head/lib/libc/stdlib/qsort.3 Tue Feb 19 23:57:39 2013 (r247014) > @@ -32,7 +32,7 @@ > .\" @(#)qsort.3 8.1 (Berkeley) 6/4/93 > .\" $FreeBSD$ > .\" > -.Dd September 30, 2003 > +.Dd February 20, 2013 > .Dt QSORT 3 > .Os > .Sh NAME > @@ -211,6 +211,52 @@ Previous versions of > did not permit the comparison routine itself to call > .Fn qsort 3 . > This is no longer true. > +.Sh EXAMPLES > +A sample program that sorts an array of > +.Vt int > +values in place using > +.Fn qsort , > +and then prints the sorted array to standard output is: > +.Bd -literal > +#include <stdio.h> > +#include <stdlib.h> > +#include <string.h> > + > +/* > + * Custom comparison function that can compare 'int' values through pointers > + * passed by qsort(3). > + */ > +static int > +int_compare(const void *p1, const void *p2) > +{ > + int *left = (int *)p1; > + int *right = (int *)p2; These should be declared const int *. And the cast shouldn't be needed in C, since void * can be assigned to any other pointer type. Cheers, matthew > + > + if (*left < *right) > + return (-1); > + else if (*left > *right) > + return (1); > + else > + return (0); > +} > + > +/* > + * Sort an array of 'int' values and print it to standard output. > + */ > +int > +main(void) > +{ > + int int_array[] = { 4, 5, 9, 3, 0, 1, 7, 2, 8, 6 }; > + const int array_size = sizeof(int_array) / sizeof(int_array[0]); > + int k; > + > + qsort(&int_array, array_size, sizeof(int), int_compare); > + for (k = 0; k < array_size; k++) > + printf(" %d", int_array[k]); > + printf("\\n"); > + exit(EXIT_SUCCESS); > +} > +.Ed > .Sh ERRORS > The > .Fn heapsort
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