libcruft-util/types/traits.hpp

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/*
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* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
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* Copyright 2012-2018 Danny Robson <danny@nerdcruft.net>
*/
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#pragma once
#include <memory>
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#include <tuple>
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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 cruft::types {
//-------------------------------------------------------------------------
template <typename TypeT, template <typename> class ...ModifierT>
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struct compose;
//-------------------------------------------------------------------------
template <typename TypeT>
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struct compose<TypeT> { using type = TypeT; };
//-------------------------------------------------------------------------
template <
typename TypeT,
template <typename> class HeadT,
template <typename> class ...TailT
>
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struct compose<TypeT, HeadT, TailT...> : public compose<
typename HeadT<TypeT>::type,
TailT...
> { };
//-------------------------------------------------------------------------
template <typename T, template <typename> class ...Args>
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using chain_t = typename compose<T, Args...>::type;
}
namespace cruft::types {
///////////////////////////////////////////////////////////////////////////
/// CXX20: An early implementation of std::identity_t and related
/// structures; useful for disabling template argument deduction, and
/// higher order template functions.
template <typename T>
struct identity { using type = T; };
//-------------------------------------------------------------------------
template <typename T>
using identity_t = typename identity<T>::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
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namespace detail {
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...);
};
//-------------------------------------------------------------------------
template <typename ResultT, typename ...Args>
struct remove_noexcept<ResultT(*const)(Args...) noexcept> {
using type = ResultT(*const)(Args...);
};
//-------------------------------------------------------------------------
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...);
};
//-------------------------------------------------------------------------
template <typename ClassT, typename ResultT, typename ...Args>
struct remove_noexcept<ResultT(ClassT::*)(Args...) const noexcept> {
using type = ResultT(ClassT::*)(Args...) const;
};
};
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//-----------------------------------------------------------------------------
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template <typename T>
struct remove_noexcept : public detail::remove_noexcept<T> { };
//-----------------------------------------------------------------------------
template <typename T>
using remove_noexcept_t = typename remove_noexcept<T>::type;
///////////////////////////////////////////////////////////////////////////////
/// removes any `const' qualifier from the supplied member function
template <typename FuncT>
struct remove_member_const {
using type = FuncT;
};
//-----------------------------------------------------------------------------
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template <typename ClassT, typename ReturnT, typename ...Args>
struct remove_member_const<ReturnT(ClassT::*const)(Args...) const> {
using type = ReturnT(ClassT::*const)(Args...);
};
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//-----------------------------------------------------------------------------
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template <typename ClassT, typename ReturnT, typename ...Args>
struct remove_member_const<ReturnT(ClassT::*)(Args...) const> {
using type = ReturnT(ClassT::*)(Args...);
};
///////////////////////////////////////////////////////////////////////////////
/// 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;
namespace detail {
template <typename T>
struct func_traits { };
//-------------------------------------------------------------------------
template <typename ClassT, typename ResultT, typename ...Args>
struct func_traits<ResultT(ClassT::*)(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...>;
};
//-------------------------------------------------------------------------
template <typename ResultT, typename ...Args>
struct func_traits<ResultT(&)(Args...)> {
using return_type = ResultT;
using argument_types = std::tuple<Args...>;
};
};
//-----------------------------------------------------------------------------
template <typename T>
struct func_traits : public ::detail::func_traits<
// we apply as many transforms as possible before palming it off to the
// detail class so that we don't have to write as many distinct cases.
::cruft::types::chain_t<T,
std::remove_cv,
std::decay,
remove_member_const,
remove_noexcept
>
> {
// we may as well record the underlying type here. it might prove useful
// to someone.
using type = T;
};
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///////////////////////////////////////////////////////////////////////////////
template <typename FunctionT>
struct function_argument_count : public std::integral_constant<
size_t,
std::tuple_size_v<
typename func_traits<FunctionT>::argument_types
>
> { };
//-----------------------------------------------------------------------------
template <typename FunctionT>
constexpr auto function_argument_count_v = function_argument_count<FunctionT>::value;
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///////////////////////////////////////////////////////////////////////////////
template <std::size_t N, typename FuncT>
struct nth_argument : std::tuple_element<
N,
typename func_traits<FuncT>::argument_types
> { };
template <std::size_t N, typename FuncT>
using nth_argument_t = typename nth_argument<N, FuncT>::type;
///////////////////////////////////////////////////////////////////////////////
template <typename T, typename = std::void_t<>>
struct is_container : public std::false_type {};
template <typename T>
struct is_container<
T,
std::void_t<
typename T::value_type,
typename T::reference,
typename T::const_reference,
typename T::iterator,
typename T::const_iterator,
typename T::difference_type,
typename T::size_type
>
> : public std::true_type {};
template <size_t N, typename ValueT>
struct is_container<std::array<ValueT,N>> : public std::true_type {};
template <typename T>
constexpr auto is_container_v = is_container<T>::value;
///////////////////////////////////////////////////////////////////////////////
#include <string>
#include <array>
#include <vector>
template <typename T>
struct is_contiguous : public std::false_type {};
template <typename CharT, typename Traits, typename Allocator>
struct is_contiguous<std::basic_string<CharT, Traits, Allocator>> : public std::true_type {};
template <typename T, std::size_t N>
struct is_contiguous<std::array<T,N>>: public std::true_type {};
template <typename T, typename Allocator>
struct is_contiguous<std::vector<T,Allocator>>: public std::true_type {};
template <typename T>
constexpr auto is_contiguous_v = is_contiguous<T>::value;
namespace cruft {
///////////////////////////////////////////////////////////////////////////////
/// stores the type of '::value_type' for a given type, or the type itself if
/// it does not have such a type.
template <typename ValueT, typename = std::void_t<>>
struct inner_type {
using type = ValueT;
};
//-----------------------------------------------------------------------------
template <typename ValueT>
struct inner_type<
ValueT,
std::void_t<typename ValueT::value_type>
> {
using type = typename ValueT::value_type;
};
//-----------------------------------------------------------------------------
template <typename ValueT>
using inner_type_t = typename inner_type<ValueT>::type;
}
///////////////////////////////////////////////////////////////////////////////
template <
template <typename...> class TemplateT,
typename QueryT
>
struct is_same_template_template : public std::false_type {};
//-----------------------------------------------------------------------------
template <
template <typename...> class TemplateT,
template <typename...> class QueryT,
typename ...Args
> struct is_same_template_template<
TemplateT,
QueryT<Args...>
> : public std::conditional_t<
std::is_same_v<
TemplateT<Args...>,
QueryT<Args...>
>,
std::true_type,
std::false_type
> { };
//-----------------------------------------------------------------------------
template <template <typename...> class TemplateT, typename QueryT>
constexpr auto is_same_template_template_v = is_same_template_template<TemplateT,QueryT>::value;
namespace cruft::traits {
/// combines an abitrary sequence of type traits into one result
template <
typename ValueT,
template <typename> class ...Traits
> struct all : public std::integral_constant<
bool,
(Traits<ValueT>::value && ...)
> { };
};
///////////////////////////////////////////////////////////////////////////////
namespace cruft {
/// tests if the type is a signed integer type
template <typename ValueT>
struct is_signed_integral : public traits::all<
ValueT, std::is_signed, std::is_integral
> { };
template <typename ValueT>
constexpr auto is_signed_integral_v = is_signed_integral<ValueT>::value;
/// tests if the type is an unsigned integer type
template <typename ValueT>
struct is_unsigned_integral : public traits::all<
ValueT, std::is_unsigned, std::is_integral
> { };
template <typename ValueT>
constexpr auto is_unsigned_integral_v = is_unsigned_integral<ValueT>::value;
/// tests if the type has the same basic fundamental type.
///
/// ie, both float, signed, unsigned, or char.
template <typename ValueA, typename ValueB>
struct is_same_basic_type {
static constexpr bool value =
(std::is_floating_point_v<ValueA> && std::is_floating_point_v<ValueB>) ||
(is_unsigned_integral_v<ValueA> && is_unsigned_integral_v<ValueB>) ||
(is_signed_integral_v<ValueA> && is_signed_integral_v<ValueB>) ||
(std::is_same_v<char,ValueA> && std::is_same_v<char,ValueB>);
};
template <typename ValueA, typename ValueB>
constexpr auto is_same_basic_type_v = is_same_basic_type<ValueA,ValueB>::value;
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/// Tests if an object is 'tuple-like'; ie, it responds to std::get,
/// std::tuple_size, and std::tuple_element.
template <typename, typename = void>
struct is_tuple_like : public std::false_type {};
template <typename T>
struct is_tuple_like<
T,
std::void_t<
decltype (std::get<0> (std::declval<T> ())),
decltype (std::tuple_size_v<T>),
std::tuple_element_t<0,T>
>
> : public std::true_type {};
template <typename T>
constexpr auto is_tuple_like_v = is_tuple_like<T>::value;
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///////////////////////////////////////////////////////////////////////////
/// Tests if a type is orderable; ie, if it supports the less than operator
///
/// We use void_t to detect the presence of an appropriate operator<
template <
typename ValueT,
typename = std::void_t<>
>
struct is_orderable : public std::false_type {};
//-------------------------------------------------------------------------
template <typename ValueT>
struct is_orderable<
ValueT,
std::void_t<
decltype (
std::declval<ValueT> () < std::declval<ValueT> ()
)
>
> : std::true_type {};
//-----------------------------------------------------------------------------------
template <typename ValueT>
constexpr auto is_orderable_v = is_orderable<ValueT>::value;
};