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Re: qsort

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Bill Cunningham wrote:
 
> double prices[]={24.45,24,21};
> 
> I want to sort them from highest to lowest.
> Still not knowing C's semantics
> well enough there's probably a simpler way
> but what kind of function would I
> want to write to pass to that last parameter of qsort?

/* BEGIN output from new.c */

From highest to lowest:
24.450000
24.000000
21.000000

/* END output from new.c */



/* BEGIN new.c */

#include <stdio.h>
#include <stdlib.h>

int 
price_comp(const void *a, const void *b)
{
    const double *aa = a;
    const double *bb = b;

    return *aa > *bb ? -1 : *aa != *bb;
}

int 
main(void)
{
    double prices[] = {24.45, 24, 21};
    double *ptr = prices;
    size_t n = sizeof prices / sizeof *prices;

    qsort(prices, n, sizeof *prices, price_comp);

    puts("\n/* BEGIN output from new.c */\n");
    puts("From highest to lowest:");
    while (n-- != 0) {
        printf("%f\n", *ptr);
        ++ptr;
    }
    puts("\n/* END output from new.c */");
    return 0;
}

/* END new.c */

-- 
pete

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qsort "Bill Cunningham" <nospam@nspam.invalid> - 2011-11-11 09:00 -0500
  Re: qsort Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-11-11 06:56 -0800
    Re: qsort Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-11-11 16:39 +0000
      Re: qsort 88888 Dihedral <dihedral88888@googlemail.com> - 2011-11-12 10:19 -0800
  Re: qsort John Gordon <gordon@panix.com> - 2011-11-11 15:20 +0000
    Re: qsort "Bill Cunningham" <nospam@nspam.invalid> - 2011-11-11 14:22 -0500
  Re: qsort pete <pfiland@mindspring.com> - 2011-11-11 20:27 -0500
    Re: qsort "Bill Cunningham" <nospam@nspam.invalid> - 2011-11-12 19:10 -0500
      Re: qsort Keith Thompson <kst-u@mib.org> - 2011-11-12 16:40 -0800
        Re: qsort "Bill Cunningham" <nospam@nspam.invalid> - 2011-11-13 01:39 -0500
          Re: qsort Ian Collins <ian-news@hotmail.com> - 2011-11-13 19:51 +1300
            Re: qsort Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-11-14 02:14 +0200
            Re: qsort Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-14 00:43 -0800
      Re: qsort pete <pfiland@mindspring.com> - 2011-11-12 22:42 -0500

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