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/* Copyright (c) 1997-2024
Ewgenij Gawrilow, Michael Joswig, and the polymake team
Technische Universität Berlin, Germany
https://polymake.org
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version: http://www.gnu.org/licenses/gpl.txt.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
--------------------------------------------------------------------------------
*/
#pragma once
#include "polymake/internal/nothing.h"
namespace pm {
// special case of trivial no-conversion
template <typename T>
class trivial_conv {
public:
typedef T argument_type;
typedef typename function_argument<T>::type result_type;
const T& operator() (const T& x) const { return x; }
T&& operator() (T&& x) const { return std::move(x); }
};
template <typename From, typename To, bool enabled=std::is_constructible<To, From>::value>
class conv_default : public nothing {};
template <typename From, typename To>
class conv_default<From, To, true> {
public:
typedef pure_type_t<From> argument_type;
typedef To result_type;
To operator() (const From& x) const { return static_cast<To>(x); }
};
/// Explicit type converter.
template <typename From, typename To>
class conv : public conv_default<From, To> {};
template <typename T>
class conv<T, T> : public trivial_conv<T> {};
template <typename From, typename To>
using is_explicitly_convertible_to
= bool_not<is_derived_from<conv<From, To>, nothing>>;
template <typename From, typename To>
using is_only_explicitly_convertible_to
= bool_constant<is_explicitly_convertible_to<From, To>::value && !std::is_convertible<From, To>::value>;
template <typename Source, typename Target>
struct can_initialize
: bool_constant< isomorphic_types<Source, Target>::value &&
( std::is_convertible<Source, Target>::value || is_explicitly_convertible_to<Source, Target>::value) > {};
template <typename T>
struct can_initialize<std::nullptr_t, T*>
: std::true_type {};
template <typename Source, typename Target>
struct can_upgrade
: bool_constant< isomorphic_types<Source, Target>::value && std::is_convertible<Source, Target>::value > {};
} // end namespace pm
// Local Variables:
// mode:C++
// c-basic-offset:3
// indent-tabs-mode:nil
// End:
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