forked from boostorg/conversion
45 lines
1.4 KiB
C++
Executable File
45 lines
1.4 KiB
C++
Executable File
// Copyright David Abrahams 2003.
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef IMPLICIT_CAST_DWA200356_HPP
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# define IMPLICIT_CAST_DWA200356_HPP
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# include <boost/mpl/identity.hpp>
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namespace boost {
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// implementation originally suggested by C. Green in
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// http://lists.boost.org/MailArchives/boost/msg00886.php
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// The use of identity creates a non-deduced form, so that the
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// explicit template argument must be supplied
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template <typename T>
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inline T implicit_cast (typename mpl::identity<T>::type x) {
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return x;
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}
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// incomplete return type now is here
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//template <typename T>
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//void implicit_cast (...);
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} // namespace boost
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// Macro for when you need a constant expression.
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// Note that 'expr' is evaluated at most once, though
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// it appears three times (provided by Gennaro Prota; see
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// http://lists.boost.org/Archives/boost/2004/05/65687.php)
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//
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#define BOOST_IMPLICIT_CAST(dest_type, expr) \
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( static_cast<dest_type>( \
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sizeof(boost::implicit_cast<dest_type>(expr)) ? \
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(expr) : (expr) \
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) \
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) /**/
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#endif // IMPLICIT_CAST_DWA200356_HPP
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