//===----------------------------------------------------------------------===//
//
//                     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.
//
//===----------------------------------------------------------------------===//

// NOTE: Older versions of clang have a bug where they fail to evalute
// string_view::at as a constant expression.
// XFAIL: clang-3.4, clang-3.3

// <string_view>

// constexpr const _CharT& at(size_type _pos) const;

#include <experimental/string_view>
#include <cassert>

template <typename CharT>
void test ( const CharT *s, size_t len ) {
    std::experimental::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 );
        }

    try { sv.at(len); } catch ( const std::out_of_range & ) { return ; }
    assert ( false );
    }
    
int main () {
    test ( "ABCDE", 5 );
    test ( "a", 1 );

    test ( L"ABCDE", 5 );
    test ( L"a", 1 );

#if __cplusplus >= 201103L
    test ( u"ABCDE", 5 );
    test ( u"a", 1 );

    test ( U"ABCDE", 5 );
    test ( U"a", 1 );
#endif

#if __cplusplus >= 201103L
    {
    constexpr std::experimental::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
}