add is_bool

[gpeterhoff]

is_bool.hpp

//	Distributed under the Boost Software License Version 1.0 https://www.boost.org/LICENSE_1_0.txt
//	Copyright Gero Peterhoff

#ifndef BOOST_TYPE_TRAITS_IS_BOOL_HPP
#define BOOST_TYPE_TRAITS_IS_BOOL_HPP

#include <boost/type_traits/remove_cvref.hpp>
#include <boost/type_traits/is_same.hpp>



namespace boost
{
template <typename Type> struct is_bool : public integral_constant
<
	bool,
	is_same<typename remove_cvref<Type>::type, bool>::value
>	{};



#if !defined(BOOST_NO_CXX17_INLINE_VARIABLES)
template <typename Type> inline constexpr bool is_bool_v = is_bool<Type>::value;
#endif
}	//	boost

#endif	//	BOOST_TYPE_TRAITS_IS_BOOL_HPP

[jzmaddock]

Clearly we can add this, but in the many years of type_traits existence, no one has ever asked for it, looks a bit too trivial to me.

[gpeterhoff]

It is therefore high time to make this available.
I don't even want to know how many people have already programmed around it ...

[pdimov]

The only use I can give for this (somewhat trivial) trait is that in Endian, a lot of the functions take "an integral type that is not bool".

It only saves one remove_cv in comparison to is_same<T, bool>, but so does is_void.