text: //===----------------------------------------------------------------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  
  // <string_view>
  
  // constexpr const _CharT& at(size_type _pos) const;
  
  #include <string_view>
  #include <stdexcept>
  #include <cassert>
  
  #include "test_macros.h"
  
  template <typename CharT>
  void test ( const CharT *s, size_t len ) {
      std::basic_string_view<CharT> sv ( s, len );
      assert ( sv.length() == len );
      for ( size_t i = 0; i < len; ++i ) {
          assert (  sv.at(i) == s[i] );
          assert ( &sv.at(i) == s + i );
      }
  
  #ifndef TEST_HAS_NO_EXCEPTIONS
      try { (void)sv.at(len); } catch ( const std::out_of_range & ) { return ; }
      assert ( false );
  #endif
  }
  
  int main(int, char**) {
      test ( "ABCDE", 5 );
      test ( "a", 1 );
  
      test ( L"ABCDE", 5 );
      test ( L"a", 1 );
  
  #if TEST_STD_VER >= 11
      test ( u"ABCDE", 5 );
      test ( u"a", 1 );
  
      test ( U"ABCDE", 5 );
      test ( U"a", 1 );
  #endif
  
  #if TEST_STD_VER >= 11
      {
      constexpr std::basic_string_view<char> sv ( "ABC", 2 );
      static_assert ( sv.length() ==  2,  "" );
      static_assert ( sv.at(0) == 'A', "" );
      static_assert ( sv.at(1) == 'B', "" );
      }
  #endif
  
    return 0;
  }
  