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Since BoostBook stylesheets were updated to pass through Doxygen anchor names to BoostBook output, references from QuickBook and manually written BoostBook docs were broken. Fix this by using classref/classname and similar tools to reference Doxygen-generated content. Also, to avoid anchor clashes between different parts of Boost.Utility docs, use proper anchor namespacing: avoid using manual anchors where possible and use fully qualified namespace where not. Fixes https://github.com/boostorg/utility/issues/110.
99 lines
3.6 KiB
Plaintext
99 lines
3.6 KiB
Plaintext
[/
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Copyright 2000 Beman Dawes & John Maddock.
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Copyright (c) 2021, Alan Freitas
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Distributed under the Boost Software License, Version 1.0.
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See accompanying file LICENSE_1_0.txt
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or copy at http://boost.org/LICENSE_1_0.txt
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]
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[section:compressed_pair Compressed Pair]
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[section Introduction]
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All of the contents of [@../../../../boost/compressed_pair.hpp `<boost/compressed_pair.hpp>`] are defined inside
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`namespace boost`.
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The class __compressed_pair__ is very similar to __std_pair__. However, if either of
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the template arguments are empty classes, then the
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[@https://en.cppreference.com/w/cpp/language/ebo ['empty base-class optimisation]]
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is applied to compress the size of the pair.
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[endsect]
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[section Synopsis]
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```cpp
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template <class T1, class T2>
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class __compressed_pair__
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{
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public:
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typedef T1 first_type;
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typedef T2 second_type;
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typedef typename __call_traits__<first_type>::param_type first_param_type;
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typedef typename __call_traits__<second_type>::param_type second_param_type;
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typedef typename __call_traits__<first_type>::reference first_reference;
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typedef typename __call_traits__<second_type>::reference second_reference;
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typedef typename __call_traits__<first_type>::const_reference first_const_reference;
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typedef typename __call_traits__<second_type>::const_reference second_const_reference;
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compressed_pair() : base() {}
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compressed_pair(first_param_type x, second_param_type y);
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explicit compressed_pair(first_param_type x);
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explicit compressed_pair(second_param_type y);
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compressed_pair& operator=(const compressed_pair&);
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first_reference first();
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first_const_reference first() const;
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second_reference second();
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second_const_reference second() const;
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void swap(compressed_pair& y);
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};
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```
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The two members of the pair can be accessed using the member functions
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`first()` and `second()`. Note that not all member functions can be
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instantiated for all template parameter types. In particular
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__compressed_pair__ can be instantiated for reference and array types,
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however in these cases the range of constructors that can be used is
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limited. If types `T1` and `T2` are the same type, then there is only
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one version of the single-argument constructor, and this constructor
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initialises both values in the pair to the passed value.
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Note that if either member is a [@https://en.cppreference.com/w/cpp/named_req/PODType POD]
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type, then that member is not zero-initialized by the __compressed_pair__ default constructor:
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it is up to you to supply an initial value for these types if you want them to have
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a default value.
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Note that __compressed_pair__ can not be instantiated if either of the
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template arguments is a union type, unless there is compiler support for
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[@boost:/libs/type_traits/index.html `boost::is_union`], or
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if [@boost:/libs/type_traits/index.html `boost::is_union`] is
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specialised for the union type.
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Finally, a word of caution for Visual C++ 6 users: if either argument is an
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empty type, then assigning to that member will produce memory corruption,
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unless the empty type has a "do nothing" assignment operator defined. This
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is due to a bug in the way VC6 generates implicit assignment operators.
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[endsect]
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[/===============]
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[xinclude tmp/compressed_pair_reference.xml]
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[/===============]
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[section Acknowledgments]
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Based on contributions by Steve Cleary, Beman Dawes, Howard Hinnant and
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John Maddock.
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Maintained by [@mailto:john@johnmaddock.co.uk John Maddock].
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[endsect]
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[endsect]
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