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Make it clear that POD's are not zero initialised.

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[SVN r29254]
This commit is contained in:
John Maddock 2005-05-28 11:51:04 +00:00
parent 1bd83d43e8
commit 6ea398c446
1 changed files with 46 additions and 69 deletions
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115
compressed_pair.htm
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@ -1,30 +1,19 @@
<html>
<head>
<meta http-equiv="Content-Type"
content="text/html; charset=iso-8859-1">
<meta name="Template"
content="C:\PROGRAM FILES\MICROSOFT OFFICE\OFFICE\html.dot">
<meta name="GENERATOR" content="Microsoft FrontPage Express 2.0">
<title>Header </title>
<boost/compressed_pair.hpp>
</head>
<body bgcolor="#FFFFFF" text="#000000" link="#0000FF"
vlink="#800080">
<h2><img src="../../boost.png" width="276" height="86">Header
&lt;<a href="../../boost/detail/compressed_pair.hpp">boost/compressed_pair.hpp</a>&gt;</h2>
<p>All of the contents of &lt;boost/compressed_pair.hpp&gt; are
defined inside namespace boost.</p>
<p>The class compressed pair is very similar to std::pair, but if
either of the template arguments are empty classes, then the
&quot;empty base-class optimisation&quot; is applied to compress
the size of the pair.</p>
<pre>template &lt;class T1, class T2&gt;
<head>
<title>Header </title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="Template" content="C:\PROGRAM FILES\MICROSOFT OFFICE\OFFICE\html.dot">
<meta name="GENERATOR" content="Microsoft FrontPage Express 2.0">
<boostcompressed_pair.hpp>
</head>
<body bgcolor="#ffffff" text="#000000" link="#0000ff" vlink="#800080">
<h2><img src="../../boost.png" width="276" height="86">Header &lt;<a href="../../boost/detail/compressed_pair.hpp">boost/compressed_pair.hpp</a>&gt;</h2>
<p>All of the contents of &lt;boost/compressed_pair.hpp&gt; are defined inside
namespace boost.</p>
<p>The class compressed pair is very similar to std::pair, but if either of the
template arguments are empty classes, then the "empty base-class optimisation"
is applied to compress the size of the pair.</p>
<pre>template &lt;class T1, class T2&gt;
class compressed_pair
{
public:
@ -52,47 +41,35 @@ public:
void swap(compressed_pair&amp; y);
};</pre>
<p>The two members of the pair can be accessed using the member
functions first() and second(). Note that not all member
functions can be instantiated for all template parameter types.
In particular compressed_pair can be instantiated for reference
and array types, however in these cases the range of constructors
that can be used are limited. If types T1 and T2 are the same
type, then there is only one version of the single-argument
constructor, and this constructor initialises both values in the
pair to the passed value.</p>
<p>Note that compressed_pair can not be instantiated if either of
the template arguments is a union type, unless there is compiler
support for boost::is_union, or if boost::is_union is specialised
for the union type.</p>
<p>Finally, a word of caution for Visual C++ 6 users: if either
argument is an empty type, then assigning to that member will
produce memory corruption, unless the empty type has a &quot;do
nothing&quot; assignment operator defined. This is due to a bug
in the way VC6 generates implicit assignment operators.</p>
<hr>
<p>Revised 08 May 2001</p>
<p>© Copyright boost.org 2000. Permission to copy, use, modify,
sell and distribute this document is granted provided this
copyright notice appears in all copies. This document is provided
&quot;as is&quot; without express or implied warranty, and with
no claim as to its suitability for any purpose.</p>
<p>Based on contributions by Steve Cleary, Beman Dawes, Howard
Hinnant and John Maddock.</p>
<p>Maintained by <a href="mailto:john@johnmaddock.co.uk">John
Maddock</a>, the latest version of this file can be found at <a
href="http://www.boost.org">www.boost.org</a>, and the boost
discussion list at <a
href="http://www.yahoogroups.com/list/boost">www.yahoogroups.com/list/boost</a>.</p>
<p>&nbsp;</p>
</body>
<p>The two members of the pair can be accessed using the member functions first()
and second(). Note that not all member functions can be instantiated for all
template parameter types. In particular compressed_pair can be instantiated for
reference and array types, however in these cases the range of constructors
that can be used are limited. If types T1 and T2 are the same type, then there
is only one version of the single-argument constructor, and this constructor
initialises both values in the pair to the passed value.</p>
<P>Note that if either member is a POD type, then that member is not
zero-initialized by the compressed_pair default constructor: it's up to you to
supply an initial value for these types if you want them to have a default
value.</P>
<p>Note that compressed_pair can not be instantiated if either of the template
arguments is a union type, unless there is compiler support for
boost::is_union, or if boost::is_union is specialised for the union type.</p>
<p>Finally, a word of caution for Visual C++ 6 users: if either argument is an
empty type, then assigning to that member will produce memory corruption,
unless the empty type has a "do nothing" assignment operator defined. This is
due to a bug in the way VC6 generates implicit assignment operators.</p>
<hr>
<p>Revised 08 May 2001</p>
<p>© Copyright boost.org 2000. Permission to copy, use, modify, sell and
distribute this document is granted provided this copyright notice appears in
all copies. This document is provided "as is" without express or implied
warranty, and with no claim as to its suitability for any purpose.</p>
<p>Based on contributions by Steve Cleary, Beman Dawes, Howard Hinnant and John
Maddock.</p>
<p>Maintained by <a href="mailto:john@johnmaddock.co.uk">John Maddock</a>, the
latest version of this file can be found at <a href="http://www.boost.org">www.boost.org</a>,
and the boost discussion list at <a href="http://www.yahoogroups.com/list/boost">www.yahoogroups.com/list/boost</a>.</p>
<p>&nbsp;</p>
</body>
</html>