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From: dietmar.kuehl@claas-solutions.de
Subject: Re: Count signature
Date: 1998/05/11
Message-ID: <6j6bro$kok$1@nnrp1.dejanews.com>#1/1
X-Deja-AN: 352157157
Approved: Fergus Henderson <fjh@cs.mu.oz.au>
References: <6j0bmk$m0v@bgtnsc03.worldnet.att.net>
X-Original-Date: Mon, 11 May 1998 08:11:37 GMT
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Newsgroups: comp.std.c++


Hi,
In article <6j0bmk$m0v@bgtnsc03.worldnet.att.net>,
  Cristian.Georgescu@worldnet.att.net wrote:
> The "count" algorithm as specified by the standard returns the
> result in a parameter passed by reference;
>
> In C++PL 3 page 526 (18.5.3)
> the same count algorithm seems to return the result as the return value
> of the function.
>
> Which information is the newest?

The definition in FDIS (final draft international standard) returns the value.
The orginal definition of 'count()' was not really satisfactory: having to
pass an object to be used as count is inconvenient at best. With the
introduction of 'iterator_traits' a better approach became available: the
'size_type' can be used to store the count and is even guaranteed to have an
appropriate size:

  template <typename It, typename T>
  typename iterator_traits<It>::size_type
  count(It begin, It end, T const &val);

The reason for the original version was simply that at this time there was
apparently no way to determine the size_type associated with the iterator.
Thus, the user was required to pass an object of appropriate type. With
'iterator_traits' the interface could be made safer (ie. the user cannot mess
up the type of the count anymore) and more convenient.

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