libstdc++-v3/testsuite/23_containers/span/deduction.cc

   1 // Copyright (C) 2020-2025 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-do compile { target c++20 } }
  19
  20 #include <span>
  21
  22 template<typename T, int N, typename U>
  23 constexpr bool is_static_span(const U&)
  24 {
  25   return std::is_same_v<std::span<T, N>, U> && N != std::dynamic_extent;
  26 }
  27
  28 template<typename T, typename U>
  29 constexpr bool is_dynamic_span(const U&)
  30 {
  31   return std::is_same_v<std::span<T>, U>;
  32 }
  33
  34 struct Range
  35 {
  36   float* begin() const;
  37   float* end() const;
  38 };
  39
  40 void
  41 test01()
  42 {
  43   const char c[] = "";
  44   int i[2]{};
  45   std::array<long, 3> a;
  46   Range r;
  47
  48   std::span s1(c);
  49   static_assert( is_static_span<const char, 1>(s1) );
  50
  51   std::span s2(i);
  52   static_assert( is_static_span<int, 2>(s2) );
  53
  54   std::span s3(a);
  55   static_assert( is_static_span<long, 3>(s3) );
  56
  57   std::span s4(const_cast<const std::array<long, 3>&>(a));
  58   static_assert( is_static_span<const long, 3>(s4) );
  59
  60   std::span s5(std::begin(i), std::end(i));
  61   static_assert( is_dynamic_span<int>(s5) );
  62
  63   std::span s6(std::cbegin(i), std::cend(i));
  64   static_assert( is_dynamic_span<const int>(s6) );
  65
  66   std::span s7(r);
  67   static_assert( is_dynamic_span<float>(s7) );
  68
  69   std::span s8(s1);
  70   static_assert( is_static_span<const char, 1>(s8) );
  71
  72   std::span s9(s2);
  73   static_assert( is_static_span<int, 2>(s9) );
  74
  75   std::span s10(const_cast<const std::span<int, 2>&>(s2));
  76   static_assert( is_static_span<int, 2>(s10) );
  77
  78   std::span s11(s5);
  79   static_assert( is_dynamic_span<int>(s11) );
  80
  81   std::span s12(const_cast<const std::span<int>&>(s5));
  82   static_assert( is_dynamic_span<int>(s12) );
  83 }