type_traits_ext.hpp File Reference

#include <algorithm>
#include <array>
#include <utility>
#include <limits>
#include <tuple>
#include <type_traits>
#include <cetl/pf17/type_traits.hpp>

Include dependency graph for type_traits_ext.hpp:

This graph shows which files directly or indirectly include this file:

Classes
struct	cetl::type_traits_ext::universal_predicate<... >
struct	cetl::type_traits_ext::find< Predicate, Ts >
struct	cetl::type_traits_ext::count< Predicate, Ts >
struct	cetl::type_traits_ext::partial< Fun, Left >
struct	cetl::type_traits_ext::is_convertible_without_narrowing< From, To, typename >
struct	cetl::type_traits_ext::is_convertible_without_narrowing< From, To, void_t< decltype(std::array< To, 1 >{{{std::declval< From >()}}})> >

Namespaces
namespace	cetl

Typedefs
template<typename...>
using	cetl::type_traits_ext::void_t

Variables
template<template< typename... > class Predicate, typename... Ts>
static constexpr std::size_t	cetl::type_traits_ext::find_v = find<Predicate, Ts...>::value
template<template< typename... > class Predicate, typename... Ts>
static constexpr std::size_t	cetl::type_traits_ext::count_v = count<Predicate, Ts...>::value
template<template< typename... > class Predicate, typename From, typename... Tos>
constexpr std::size_t	cetl::type_traits_ext::best_conversion_index_v

Detailed Description

Type traits extensions not found in C++ standards.

This is mostly needed for internal use in the library, but can also be useful for users.

Copyright

Copyright (C) OpenCyphal Development Team <opencyphal.org> Copyright Amazon.com Inc. or its affiliates. SPDX-License-Identifier: MIT

Typedef Documentation

void_t

template<typename...>

using cetl::pf17::void_t

Implementation of std::void_t.

Variable Documentation

best_conversion_index_v

template<template< typename... > class Predicate, typename From, typename... Tos>

std::size_t cetl::type_traits_ext::best_conversion_index_v

constexpr

Initial value:

=
detail::best_conversion_index::impl<Predicate, From, detail::best_conversion_index::types<Tos...>>::value

Index of the type in the Tos list selected by overload resolution for the expression Fun(std::forward<T>(t)) if there was an overload of imaginary function Fun(T_i) for every T_i from Tos... in scope at the same time.

The Predicate is an unary template that, upon successful instantiation with a single argument being a type from the Tos typelist, contains a static member value whose value is truth if the conversion is a valid candidate for acceptance and false if the conversion should not be considered even if it is otherwise valid. The predicate is defined as a variadic template for enhanced composability, as a variadic template template argument can accept both variadic and non-variadic parameters, even if it is only instantiated with one parameter.

Hint: to weed out narrowing conversions, use is_convertible_without_narrowing in the predicate.

If no suitable conversion is available, or the best conversion is ambiguous, the value is std::numeric_limits<std::size_t>::max(). One way to get this error is to choose between long and int on a platform where they have the same size.

best_conversion_index_v<universal_predicate, long, float> == 0
best_conversion_index_v<universal_predicate, float, long, float, bool> == 1
best_conversion_index_v<universal_predicate, int, long, float, bool> == ambiguity
 
best_conversion_index_v<std::is_signed, long, unsigned char, long, unsigned long> == 1
best_conversion_index_v<std::is_unsigned, long, signed char, long, unsigned long> == 2
best_conversion_index_v<std::is_volatile, char, int, const int, volatile int> == 2
 
best_conversion_index_v<partial<is_convertible_without_narrowing, int>::template type, int, float, bool, long> == 2
 
struct foo { foo(bool); };
best_conversion_index_v<universal_predicate, char, foo, int> == 1
best_conversion_index_v<universal_predicate, char, foo> == 0
 
best_conversion_index_v<partial<is_convertible_without_narrowing, char>::template type, char, foo, int> == 1
best_conversion_index_v<partial<is_convertible_without_narrowing, char>::template type, char, foo> == unavailable
best_conversion_index_v<partial<is_convertible_without_narrowing, bool>::template type, bool, foo> == 0

count_v

template<template< typename... > class Predicate, typename... Ts>

std::size_t cetl::type_traits_ext::count_v = count<Predicate, Ts...>::value

staticconstexpr

Alias for count.

static_assert(count_v<std::is_integral, int, char, double, std::int64_t, std::int16_t, std::int8_t> == 5, "");
static_assert(count_v<std::is_integral, double, float, std::int64_t, std::int16_t, std::int8_t> == 3, "");
static_assert(count_v<std::is_integral, double, float> == 0, "");

find_v

template<template< typename... > class Predicate, typename... Ts>

std::size_t cetl::type_traits_ext::find_v = find<Predicate, Ts...>::value

staticconstexpr

Alias for find.

/code static_assert(find_v<std::is_integral, int, char, double, std::int64_t, std::int16_t, std::int8_t> == 0, ""); static_assert(find_v<std::is_integral, double, float, std::int64_t, std::int16_t, std::int8_t> == 2, ""); static_assert(find_v<std::is_integral, double, float> == std::numeric_limits<std::size_t>::max(), ""); /endcode