What is the rational for using the _LIBCPP_BOOL_CONSTANT macro?
On Mon, May 18, 2015 at 7:21 PM, Marshall Clow <[email protected]> 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> > > > _______________________________________________ > cfe-commits mailing list > [email protected] > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits _______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
