101 lines
2.9 KiB
C++
101 lines
2.9 KiB
C++
// Copyright Daniel Wallin, David Abrahams 2005.
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// Copyright Cromwell D. Enage 2017.
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// Distributed under the Boost Software License, Version 1.0.
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// (See 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 BOOST_PARAMETER_AUX_DEFAULT_HPP
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#define BOOST_PARAMETER_AUX_DEFAULT_HPP
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namespace boost { namespace parameter { namespace aux {
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// A wrapper for the default value passed by the user when resolving
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// the value of the parameter with the given Keyword
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template <typename Keyword, typename Value>
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struct default_
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{
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inline BOOST_CONSTEXPR default_(Value& x) : value(x)
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{
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}
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Value& value;
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};
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}}} // namespace boost::parameter::aux
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#include <boost/parameter/config.hpp>
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namespace boost { namespace parameter { namespace aux {
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// lazy_default -- A wrapper for the default value computation function
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// passed by the user when resolving the value of the parameter with the
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// given keyword.
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#if BOOST_WORKAROUND(__EDG_VERSION__, <= 300)
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// These compilers need a little extra help with overload resolution;
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// we have empty_arg_list's operator[] accept a base class
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// to make that overload less preferable.
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template <typename KW, typename DefaultComputer>
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struct lazy_default_base
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{
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inline BOOST_CONSTEXPR lazy_default_base(DefaultComputer& x)
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: compute_default(x)
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{
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}
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DefaultComputer& compute_default;
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};
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template <typename KW, typename DefaultComputer>
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struct lazy_default
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: ::boost::parameter::aux::lazy_default_base<KW,DefaultComputer>
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{
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inline BOOST_CONSTEXPR lazy_default(DefaultComputer& x)
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: ::boost::parameter::aux::lazy_default_base<KW,DefaultComputer>(x)
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{
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}
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};
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#else // !BOOST_WORKAROUND(__EDG_VERSION__, <= 300)
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template <typename KW, typename DefaultComputer>
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struct lazy_default
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{
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inline BOOST_CONSTEXPR lazy_default(DefaultComputer& x)
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: compute_default(x)
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{
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}
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DefaultComputer& compute_default;
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};
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#endif // EDG workarounds needed.
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}}} // namespace boost::parameter::aux
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#if BOOST_WORKAROUND(__EDG_VERSION__, <= 300)
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#define BOOST_PARAMETER_lazy_default_fallback \
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::boost::parameter::aux::lazy_default_base
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/**/
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#else
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#define BOOST_PARAMETER_lazy_default_fallback \
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::boost::parameter::aux::lazy_default
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/**/
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#endif
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#if defined(BOOST_PARAMETER_HAS_PERFECT_FORWARDING)
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#include <utility>
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namespace boost { namespace parameter { namespace aux {
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template <typename Keyword, typename Value>
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struct default_r_
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{
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inline BOOST_CONSTEXPR default_r_(Value&& x)
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: value(::std::forward<Value>(x))
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{
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}
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Value&& value;
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};
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}}} // namespace boost::parameter::aux
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#endif // BOOST_PARAMETER_HAS_PERFECT_FORWARDING
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#endif // include guard
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