libcruft-util/types/traits.hpp

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/*
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* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
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* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright 2012-2017 Danny Robson <danny@nerdcruft.net>
*/
#ifndef CRUFT_UTIL_TYPES_TRAITS_HPP
#define CRUFT_UTIL_TYPES_TRAITS_HPP
#include <memory>
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#include <type_traits>
///////////////////////////////////////////////////////////////////////////////
/// applies a series of type-modifiers to a provided type.
///
/// modifiers are applied in the order they are provided.
///
/// use without any modifiers results in the identity modifier.
namespace util {
//-------------------------------------------------------------------------
template <typename TypeT, template <typename> class ...ModifierT>
struct chain;
//-------------------------------------------------------------------------
template <typename TypeT>
struct chain<TypeT> { using type = TypeT; };
//-------------------------------------------------------------------------
template <
typename TypeT,
template <typename> class HeadT,
template <typename> class ...TailT
>
struct chain<TypeT, HeadT, TailT...> : public chain<
typename HeadT<TypeT>::type,
TailT...
> { };
//-------------------------------------------------------------------------
template <typename T, template <typename> class ...Args>
using chain_t = typename chain<T, Args...>::type;
}
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///////////////////////////////////////////////////////////////////////////////
template <typename T> struct is_dereferencable : std::false_type { };
template <typename T> struct is_dereferencable<T*> : std::true_type { };
template <typename T> struct is_dereferencable<std::unique_ptr<T>> : std::true_type { };
template <typename T> struct is_dereferencable<std::shared_ptr<T>> : std::true_type { };
template <typename T> struct is_dereferencable<std::weak_ptr<T>> : std::true_type { };
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///////////////////////////////////////////////////////////////////////////////
template <typename T> struct dereferenced_type {
typedef typename std::enable_if<
std::is_pointer<T>::value,
std::remove_pointer<T>
>::type type;
};
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//-----------------------------------------------------------------------------
template <typename T> struct dereferenced_type<std::unique_ptr<T>> { typedef T type; };
template <typename T> struct dereferenced_type<std::shared_ptr<T>> { typedef T type; };
template <typename T> struct dereferenced_type<std::weak_ptr<T>> { typedef T type; };
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///////////////////////////////////////////////////////////////////////////////
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/// find the unsigned version of a type if one exists
template <typename T>
struct try_unsigned
{
typedef typename std::make_unsigned<T>::type type;
};
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//-----------------------------------------------------------------------------
template <> struct try_unsigned<double> { typedef double type; };
template <> struct try_unsigned<float > { typedef float type; };
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///////////////////////////////////////////////////////////////////////////////
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/// find the signed version of a type if one exists
template <typename T>
struct try_signed
{
typedef typename std::make_signed<T>::type type;
};
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//-----------------------------------------------------------------------------
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template <> struct try_signed<double> { typedef double type; };
template <> struct try_signed<float > { typedef float type; };
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///////////////////////////////////////////////////////////////////////////////
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/// checks if a type can be converted in all cases without modification
template <typename T, typename U> struct is_lossless_cast : std::enable_if<
std::is_integral<T>::value &&
std::is_integral<U>::value &&
std::is_signed<T>::value == std::is_signed<U>::value &&
sizeof (T) <= sizeof (U),
std::true_type
>::value { };
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///////////////////////////////////////////////////////////////////////////////
template <typename T> struct remove_restrict { using type = T; };
template <typename T> struct remove_restrict<T *restrict> { using type = T*; };
template <typename T>
using remove_restrict_t = typename remove_restrict<T>::type;
///////////////////////////////////////////////////////////////////////////////
/// removes the noexcept type specifier from invokable types
template <typename T>
struct remove_noexcept
{ using type = T; };
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//-----------------------------------------------------------------------------
template <typename ResultT, typename ...Args>
struct remove_noexcept<ResultT(&)(Args...) noexcept> {
using type = ResultT(&)(Args...);
};
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//-----------------------------------------------------------------------------
template <typename ResultT, typename ...Args>
struct remove_noexcept<ResultT(*)(Args...) noexcept> {
using type = ResultT(*)(Args...);
};
//-----------------------------------------------------------------------------
template <typename ClassT, typename ResultT, typename ...Args>
struct remove_noexcept<ResultT(ClassT::*)(Args...) noexcept> {
using type = ResultT(ClassT::*)(Args...);
};
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//-----------------------------------------------------------------------------
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template <typename T>
using remove_noexcept_t = typename remove_noexcept<T>::type;
///////////////////////////////////////////////////////////////////////////////
/// type traits class for querying invokable type return values and argument
/// types.
///
/// if the type is invokable the alias `return_type' will be defined for the
/// return type, and the alias tuple `argument_types' will be defined for the
/// arguments;
template <typename T>
struct func_traits : public func_traits<remove_noexcept_t<T>> { };
//-----------------------------------------------------------------------------
template <typename ClassT, typename ResultT, typename ...Args>
struct func_traits<ResultT(ClassT::*)(Args...) const> {
using return_type = ResultT;
using argument_types = std::tuple<Args...>;
};
//-----------------------------------------------------------------------------
template <typename ResultT, typename ...Args>
struct func_traits<ResultT(*)(Args...)> {
using return_type = ResultT;
using argument_types = std::tuple<Args...>;
};
//-----------------------------------------------------------------------------
template <typename ResultT, typename ...Args>
struct func_traits<ResultT(&)(Args...)> {
using return_type = ResultT;
using argument_types = std::tuple<Args...>;
};
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#endif