[libcxx] r237636 - Add support for N4389 - std::bool_constant
Eric Fiselier
eric at efcs.ca
Tue May 19 07:19:33 PDT 2015
What is the rational for using the _LIBCPP_BOOL_CONSTANT macro?
On Mon, May 18, 2015 at 7:21 PM, Marshall Clow <mclow.lists at gmail.com> wrote:
> Author: marshall
> Date: Mon May 18 18:21:06 2015
> New Revision: 237636
>
> URL: http://llvm.org/viewvc/llvm-project?rev=237636&view=rev
> Log:
> Add support for N4389 - std::bool_constant
>
> Added:
> libcxx/trunk/test/std/utilities/meta/meta.hel/bool_constant.pass.cpp
> Modified:
> libcxx/trunk/include/ratio
> libcxx/trunk/include/type_traits
> libcxx/trunk/www/cxx1z_status.html
>
> Modified: libcxx/trunk/include/ratio
> URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/ratio?rev=237636&r1=237635&r2=237636&view=diff
> ==============================================================================
> --- libcxx/trunk/include/ratio (original)
> +++ libcxx/trunk/include/ratio Mon May 18 18:21:06 2015
> @@ -398,11 +398,11 @@ struct _LIBCPP_TYPE_VIS_ONLY ratio_subtr
>
> template <class _R1, class _R2>
> struct _LIBCPP_TYPE_VIS_ONLY ratio_equal
> - : public integral_constant<bool, _R1::num == _R2::num && _R1::den == _R2::den> {};
> + : public _LIBCPP_BOOL_CONSTANT((_R1::num == _R2::num && _R1::den == _R2::den)) {};
>
> template <class _R1, class _R2>
> struct _LIBCPP_TYPE_VIS_ONLY ratio_not_equal
> - : public integral_constant<bool, !ratio_equal<_R1, _R2>::value> {};
> + : public _LIBCPP_BOOL_CONSTANT((!ratio_equal<_R1, _R2>::value)) {};
>
> // ratio_less
>
> @@ -461,19 +461,19 @@ struct __ratio_less<_R1, _R2, -1LL, -1LL
>
> template <class _R1, class _R2>
> struct _LIBCPP_TYPE_VIS_ONLY ratio_less
> - : public integral_constant<bool, __ratio_less<_R1, _R2>::value> {};
> + : public _LIBCPP_BOOL_CONSTANT((__ratio_less<_R1, _R2>::value)) {};
>
> template <class _R1, class _R2>
> struct _LIBCPP_TYPE_VIS_ONLY ratio_less_equal
> - : public integral_constant<bool, !ratio_less<_R2, _R1>::value> {};
> + : public _LIBCPP_BOOL_CONSTANT((!ratio_less<_R2, _R1>::value)) {};
>
> template <class _R1, class _R2>
> struct _LIBCPP_TYPE_VIS_ONLY ratio_greater
> - : public integral_constant<bool, ratio_less<_R2, _R1>::value> {};
> + : public _LIBCPP_BOOL_CONSTANT((ratio_less<_R2, _R1>::value)) {};
>
> template <class _R1, class _R2>
> struct _LIBCPP_TYPE_VIS_ONLY ratio_greater_equal
> - : public integral_constant<bool, !ratio_less<_R1, _R2>::value> {};
> + : public _LIBCPP_BOOL_CONSTANT((!ratio_less<_R1, _R2>::value)) {};
>
> template <class _R1, class _R2>
> struct __ratio_gcd
>
> Modified: libcxx/trunk/include/type_traits
> URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/type_traits?rev=237636&r1=237635&r2=237636&view=diff
> ==============================================================================
> --- libcxx/trunk/include/type_traits (original)
> +++ libcxx/trunk/include/type_traits Mon May 18 18:21:06 2015
> @@ -19,8 +19,13 @@ namespace std
>
> // helper class:
> template <class T, T v> struct integral_constant;
> - typedef integral_constant<bool, true> true_type;
> - typedef integral_constant<bool, false> false_type;
> + typedef integral_constant<bool, true> true_type; // C++11
> + typedef integral_constant<bool, false> false_type; // C++11
> +
> + template <bool B> // C++14
> + using bool_constant = integral_constant<bool, B>; // C++14
> + typedef bool_constant<true> true_type; // C++14
> + typedef bool_constant<false> false_type; // C++14
>
> // helper traits
> template <bool, class T = void> struct enable_if;
> @@ -260,8 +265,16 @@ struct _LIBCPP_TYPE_VIS_ONLY integral_co
> template <class _Tp, _Tp __v>
> _LIBCPP_CONSTEXPR const _Tp integral_constant<_Tp, __v>::value;
>
> -typedef integral_constant<bool, true> true_type;
> -typedef integral_constant<bool, false> false_type;
> +#if _LIBCPP_STD_VER > 14
> +template <bool __b>
> +using bool_constant = integral_constant<bool, __b>;
> +#define _LIBCPP_BOOL_CONSTANT(__b) bool_constant<(__b)>
> +#else
> +#define _LIBCPP_BOOL_CONSTANT(__b) integral_constant<bool,(__b)>
> +#endif
> +
> +typedef _LIBCPP_BOOL_CONSTANT(true) true_type;
> +typedef _LIBCPP_BOOL_CONSTANT(false) false_type;
>
> // is_const
>
> @@ -679,7 +692,7 @@ template <class _Tp> using add_pointer_t
> // is_signed
>
> template <class _Tp, bool = is_integral<_Tp>::value>
> -struct __libcpp_is_signed_impl : public integral_constant<bool, _Tp(-1) < _Tp(0)> {};
> +struct __libcpp_is_signed_impl : public _LIBCPP_BOOL_CONSTANT(_Tp(-1) < _Tp(0)) {};
>
> template <class _Tp>
> struct __libcpp_is_signed_impl<_Tp, false> : public true_type {}; // floating point
> @@ -694,7 +707,7 @@ template <class _Tp> struct _LIBCPP_TYPE
> // is_unsigned
>
> template <class _Tp, bool = is_integral<_Tp>::value>
> -struct __libcpp_is_unsigned_impl : public integral_constant<bool, _Tp(0) < _Tp(-1)> {};
> +struct __libcpp_is_unsigned_impl : public _LIBCPP_BOOL_CONSTANT(_Tp(0) < _Tp(-1)) {};
>
> template <class _Tp>
> struct __libcpp_is_unsigned_impl<_Tp, false> : public false_type {}; // floating point
>
> Added: libcxx/trunk/test/std/utilities/meta/meta.hel/bool_constant.pass.cpp
> URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/std/utilities/meta/meta.hel/bool_constant.pass.cpp?rev=237636&view=auto
> ==============================================================================
> --- libcxx/trunk/test/std/utilities/meta/meta.hel/bool_constant.pass.cpp (added)
> +++ libcxx/trunk/test/std/utilities/meta/meta.hel/bool_constant.pass.cpp Mon May 18 18:21:06 2015
> @@ -0,0 +1,32 @@
> +//===----------------------------------------------------------------------===//
> +//
> +// The LLVM Compiler Infrastructure
> +//
> +// This file is dual licensed under the MIT and the University of Illinois Open
> +// Source Licenses. See LICENSE.TXT for details.
> +//
> +//===----------------------------------------------------------------------===//
> +
> +// type_traits
> +
> +// bool_constant
> +
> +#include <type_traits>
> +#include <cassert>
> +
> +int main()
> +{
> +#if __cplusplus > 201402L
> + typedef std::bool_constant<true> _t;
> + static_assert(_t::value, "");
> + static_assert((std::is_same<_t::value_type, bool>::value), "");
> + static_assert((std::is_same<_t::type, _t>::value), "");
> + static_assert((_t() == true), "");
> +
> + typedef std::bool_constant<false> _f;
> + static_assert(!_f::value, "");
> + static_assert((std::is_same<_f::value_type, bool>::value), "");
> + static_assert((std::is_same<_f::type, _f>::value), "");
> + static_assert((_f() == false), "");
> +#endif
> +}
>
> Modified: libcxx/trunk/www/cxx1z_status.html
> URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/www/cxx1z_status.html?rev=237636&r1=237635&r2=237636&view=diff
> ==============================================================================
> --- libcxx/trunk/www/cxx1z_status.html (original)
> +++ libcxx/trunk/www/cxx1z_status.html Mon May 18 18:21:06 2015
> @@ -64,7 +64,7 @@
> <tr><td><a href="http://wiki.edg.com/twiki/pub/Wg21urbana-champaign/StrawPolls/n4285.html">N4285</a></td><td>CWG</td></td><td>Cleanup for exception-specification and throw-expression.</td><td>Urbana</td><td></td><td></td></tr>
> <tr><td></td><td></td><td></td><td></td><td></td><td></td></tr>
> <tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4387">N4387</a></td><td>LWG</td></td><td>improving pair and tuple</td><td>Lenexa</td><td></td><td></td></tr>
> - <tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4389">N4389</a></td><td>LWG</td></td><td>bool_constant</td><td>Lenexa</td><td></td><td></td></tr>
> + <tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4389">N4389</a></td><td>LWG</td></td><td>bool_constant</td><td>Lenexa</td><td></td><td>Complete</td></tr>
> <tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4508">N4508</a></td><td>LWG</td></td><td>shared_mutex for C++17</td><td>Lenexa</td><td></td><td></td></tr>
> <tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4366">N4366</a></td><td>LWG</td></td><td>LWG 2228 missing SFINAE rule</td><td>Lenexa</td><td></td><td></td></tr>
> <tr><td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4510">N4510</a></td><td>LWG</td></td><td>Minimal incomplete type support for standard containers, revision 4</td><td>Lenexa</td><td></td><td></td></tr>
>
>
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