mirror of https://github.com/CGAL/cgal
110 lines
3.1 KiB
C++
110 lines
3.1 KiB
C++
// Copyright (c) 2008 INRIA Sophia-Antipolis (France).
|
|
// All rights reserved.
|
|
//
|
|
// This file is part of CGAL (www.cgal.org)
|
|
//
|
|
// $URL$
|
|
// $Id$
|
|
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
|
|
//
|
|
// Author(s) : Sylvain Pion
|
|
|
|
#ifndef CGAL_ARRAY_H
|
|
#define CGAL_ARRAY_H
|
|
|
|
#include <CGAL/config.h>
|
|
#include <CGAL/type_traits.h>
|
|
#include <array>
|
|
#include <utility>
|
|
|
|
namespace CGAL {
|
|
|
|
// The make_array() function simply constructs an std::array.
|
|
// It is needed for cases where a std::array is used as a class data
|
|
// member and you want to initialize it in the member initializers list.
|
|
// It is also optimized: no spurious copies of the objects are made,
|
|
// provided the compiler does the NRVO. So this is better than
|
|
// default construction followed by assignment.
|
|
|
|
// I proposed it for Boost.Array, but it has not been integrated so far.
|
|
// See the thread starting at
|
|
// https://lists.boost.org/Archives/boost/2006/08/109003.php
|
|
//
|
|
// C++0x has it under discussion here :
|
|
// https://www.open-std.org/jtc1/sc22/wg21/docs/lwg-active.html#851
|
|
|
|
// Hopefully C++0x will fix this properly with initializer_lists.
|
|
// So, it's temporary, therefore I do not document it and keep it internal.
|
|
|
|
// NOTE : The above is actually untrue ! It is possible to do :
|
|
// struct S2 {
|
|
// typedef std::array<M,2> Ar;
|
|
// Ar m;
|
|
// S2 (const M&a) : m ((Ar) { { a, a } }) {}
|
|
// };
|
|
// without spurious copies... Except VC++ does not eat it :-(
|
|
|
|
// It's also untrue that this is not documented... It is !
|
|
|
|
template <typename T, typename ...Args>
|
|
struct Make_array_element_type {
|
|
using type = T;
|
|
};
|
|
|
|
template <typename ...Args>
|
|
struct Make_array_element_type<void, Args...> {
|
|
using type = typename std::common_type_t<Args...>;
|
|
};
|
|
|
|
template <typename T, typename ...Args>
|
|
using Make_array_element_type_t = typename Make_array_element_type<T, Args...>::type;
|
|
|
|
template<typename T = void, typename... Args>
|
|
constexpr
|
|
std::array<Make_array_element_type_t<T, Args...>, sizeof...(Args) >
|
|
make_array(Args&& ... args)
|
|
{
|
|
using Target_type = Make_array_element_type_t<T, Args...>;
|
|
|
|
// MSVC 2017 chokes on the following code, so we simplify it for this compiler
|
|
// See https://godbolt.org/z/7Y34Y1c53
|
|
#if ! defined(_MSC_VER) || (_MSC_VER > 1916)
|
|
if constexpr ( (CGAL::is_convertible_without_narrowing_v<cpp20::remove_cvref_t<Args>, Target_type>&&...) )
|
|
return {{ std::forward<Args>(args)... }};
|
|
else
|
|
#endif // not MSVC or MSVC 2019 or later
|
|
{
|
|
std::array< Target_type, sizeof...(Args) > a = { { static_cast<Target_type>(args)... } };
|
|
return a;
|
|
}
|
|
}
|
|
|
|
// Functor version
|
|
struct Construct_array
|
|
{
|
|
template <typename... Args>
|
|
constexpr
|
|
decltype(auto)
|
|
operator()(Args&& ... args) const
|
|
{
|
|
return make_array( std::forward<Args>(args)... );
|
|
}
|
|
};
|
|
|
|
template <std::size_t...Is, typename T>
|
|
constexpr std::array<T, sizeof...(Is)>
|
|
make_filled_array_aux(const T& value, std::index_sequence<Is...>)
|
|
{
|
|
return {(static_cast<void>(Is), value)...};
|
|
}
|
|
|
|
template <std::size_t N, typename T>
|
|
constexpr std::array<T, N> make_filled_array(const T& value)
|
|
{
|
|
return make_filled_array_aux(value, std::make_index_sequence<N>());
|
|
}
|
|
|
|
} //namespace CGAL
|
|
|
|
#endif // CGAL_ARRAY_H
|