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integral_constant: As per std: Add operator().

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In the C++ Standard Library, `std::integral_constant` has `operator()`:

https://timsong-cpp.github.io/cppwp/meta.help

We hereby add `operator()` for the Boost version.
This commit is contained in:
Adder
2025-01-07 00:43:06 +02:00
committed by John Maddock
parent f31a9da4d8
commit 4126ca650c
2 changed files with 30 additions and 0 deletions
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2
include/boost/type_traits/integral_constant.hpp
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@ -64,6 +64,7 @@ namespace boost{
return *static_cast<const mpl::integral_c<T, val>*>(pdata);
}
BOOST_CONSTEXPR operator T()const BOOST_NOEXCEPT { return val; }
BOOST_CONSTEXPR T operator()()const BOOST_NOEXCEPT { return val; }
};
template <class T, T val>
@ -84,6 +85,7 @@ namespace boost{
return *static_cast<const mpl::bool_<val>*>(pdata);
}
BOOST_CONSTEXPR operator bool()const BOOST_NOEXCEPT { return val; }
BOOST_CONSTEXPR bool operator()()const BOOST_NOEXCEPT { return val; }
};
template <bool val>

28
test/integral_constant_test.cpp Executable file
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@ -0,0 +1,28 @@
// Copyright 2025 DoctorNoobingstoneIPresume
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
#include <boost/type_traits/integral_constant.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/static_assert.hpp>
int main ()
{
// [2025-01-07] Adapted from example in https://en.cppreference.com/w/cpp/types/integral_constant ...
using two_t = boost::integral_constant <int, 2>;
using four_t = boost::integral_constant <int, 4>;
BOOST_STATIC_ASSERT ((! boost::is_same <two_t, four_t>::value));
BOOST_STATIC_ASSERT ((two_t::value * 2 == four_t::value));
BOOST_STATIC_ASSERT ((two_t () << 1 == four_t ()));
BOOST_STATIC_ASSERT ((two_t () () << 1 == four_t () ()));
enum class E {e0, e1};
using c0 = boost::integral_constant <E, E::e0>;
using c1 = boost::integral_constant <E, E::e1>;
BOOST_STATIC_ASSERT ((c0::value != E::e1));
BOOST_STATIC_ASSERT ((c0 () == E::e0));
BOOST_STATIC_ASSERT ((boost::is_same <c1, c1>::value));
}