libstdc++-v3/testsuite/18_support/comparisons/algorithms/strong_order.cc

   1 // Copyright (C) 2019-2022 Free Software Foundation, Inc.
   2 //
   3 // This file is part of the GNU ISO C++ Library.  This library is free
   4 // software; you can redistribute it and/or modify it under the
   5 // terms of the GNU General Public License as published by the
   6 // Free Software Foundation; either version 3, or (at your option)
   7 // any later version.
   8
   9 // This library is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13
  14 // You should have received a copy of the GNU General Public License along
  15 // with this library; see the file COPYING3.  If not see
  16 // <http://www.gnu.org/licenses/>.
  17
  18 // { dg-options "-std=gnu++2a" }
  19 // { dg-do compile { target c++2a } }
  20
  21 #include <compare>
  22 #include <limits>
  23
  24 using std::strong_order;
  25 using std::strong_ordering;
  26
  27 static_assert( strong_order(1, 2) == strong_ordering::less );
  28 static_assert( strong_order(1, 1) == strong_ordering::equal );
  29 static_assert( strong_order(2, 1) == strong_ordering::greater );
  30 static_assert( noexcept(strong_order(1, 1)) );
  31
  32 constexpr strong_ordering different_cv_quals(int i, const int j)
  33 {
  34   return strong_order(i, j);
  35 }
  36 static_assert( different_cv_quals(42, 999) == strong_ordering::less );
  37 static_assert( different_cv_quals(-999, -999) == strong_ordering::equal );
  38 static_assert( different_cv_quals(-99, -111) == strong_ordering::greater );
  39
  40 namespace N
  41 {
  42   struct X { int i; };
  43
  44   constexpr strong_ordering operator<=>(X l, X r)
  45   {
  46     if (l.i < 0 && r.i < 0)
  47       return strong_ordering::equivalent;
  48     return r.i <=> l.i;
  49   }
  50
  51   constexpr bool operator==(X l, X r) { return std::is_eq(l <=> r); }
  52
  53   static_assert(std::three_way_comparable<X>);
  54 }
  55 using N::X;
  56
  57 static_assert( strong_order(X{1}, X{1}) == strong_ordering::equal );
  58 static_assert( strong_order(X{-1}, X{-2}) == strong_ordering::equivalent );
  59 static_assert( strong_order(X{1}, X{2}) == strong_ordering::greater );
  60 static_assert( !noexcept(strong_order(X{1}, X{2})) );