delorie.com/archives/browse.cgi   search  
Mail Archives: djgpp/1999/03/07/15:46:08

From: Dave Bird <dave AT xemu DOT demon DOT co DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Pointers to functions.
Date: Sun, 7 Mar 1999 18:18:30 +0000
Organization: very little
Message-ID: <u79p7SA2Ls42EwHc@xemu.demon.co.uk>
References: <7b9jku$o7o$1 AT news6 DOT svr DOT pol DOT co DOT uk> <36D9BD2F DOT A05C8E55 AT cartsys DOT com>
<CqyGOCASqC42EwDb AT dunvegan1 DOT demon DOT co DOT uk> <7br6n8$897$1 AT news6 DOT svr DOT pol DOT co DOT uk>
<7bu8hk$6b6$1 AT camel19 DOT mindspring DOT com>
NNTP-Posting-Host: xemu.demon.co.uk
X-NNTP-Posting-Host: xemu.demon.co.uk:158.152.196.209
X-Trace: news.demon.co.uk 920837909 nnrp-10:15236 NO-IDENT xemu.demon.co.uk:158.152.196.209
X-Complaints-To: abuse AT demon DOT net
MIME-Version: 1.0
X-Newsreader: Turnpike (32) Version 4.01 <dQumtnY$x4rJ2u5tL5fS$n2vuP>
Lines: 26
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

In ar<7bu8hk$6b6$1 AT camel19 DOT mindspring DOT com>, Lark <rlark AT at DOT mbhs> writes
>
>What is the purpose(point, if you will) of having a pointer to a function?

 so that a 'C' variable can indicate a 'variable' sort of function
 i.e. a different actual function to be used in different contexts.

 For example:

 You might want to write a clever sort algorithm which can sort many
 different kinds of data. Let's assume it can cope correctly with
 the varying lengths of data and find the next record all right.

 Then you might have a parameter which was  int (*compare)();
 i.e. what compare points at is a function that returns int
 being -1 0 +1 for less or equal or greater.  Of course it
 would be a different function depending on whether the objects
 you were sorting were strings, 128bit integers, polygons, 
 or whatever.



-- 
   ^-^-^-@@-^-;-^   http://www.xemu.demon.co.uk/
        (..)__u     news:alt.smoking.mooses

- Raw text -


  webmaster     delorie software   privacy  
  Copyright 2019   by DJ Delorie     Updated Jul 2019