reverse.cpp:20:12: error: no viable conversion from '<lambda at
      reverse.cpp:21:9>' to 'std::string' (aka 'basic_string<char,
      char_traits<char>, allocator<char> >')
    return std::accumulate(words.begin(), words.end(),
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:1191:5: note:
      candidate constructor not viable: no known conversion from '<lambda at
      reverse.cpp:21:9>' to 'const std::__1::basic_string<char> &' for 1st
      argument
    basic_string(const basic_string& __str);
    ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:1195:5: note:
      candidate constructor not viable: no known conversion from '<lambda at
      reverse.cpp:21:9>' to 'std::__1::basic_string<char> &&' for 1st argument
    basic_string(basic_string&& __str)
    ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:1200:31: note:
      candidate constructor not viable: no known conversion from '<lambda at
      reverse.cpp:21:9>' to 'const value_type *' (aka 'const char *') for 1st
      argument
    _LIBCPP_INLINE_VISIBILITY basic_string(const value_type* __s);
                              ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:1221:5: note:
      candidate constructor not viable: no known conversion from '<lambda at
      reverse.cpp:21:9>' to 'initializer_list<value_type>' for 1st argument
    basic_string(initializer_list<value_type> __il);
    ^
reverse.cpp:21:9: note: candidate function
        [](const std::string& s1, const std::string& s2) {
        ^
In file included from reverse.cpp:3:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/numeric:75:25: error:
      invalid operands to binary expression ('<lambda at reverse.cpp:21:9>' and
      'std::__1::basic_string<char>')
        __init = __init + *__first;
                 ~~~~~~ ^ ~~~~~~~~
reverse.cpp:20:17: note: in instantiation of function template specialization
      'std::__1::accumulate<std::__1::__wrap_iter<std::__1::basic_string<char>
      *>, <lambda at reverse.cpp:21:9> >' requested here
    return std::accumulate(words.begin(), words.end(),
                ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:3906:1: note:
      candidate template ignored: deduced conflicting types for parameter
      '_CharT' ('<lambda at reverse.cpp:21:9>' vs. 'char')
operator+(_CharT __lhs, const basic_string<_CharT,_Traits,_Allocator>& __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:3975:1: note:
      candidate template ignored: deduced conflicting types for parameter
      '_CharT' ('<lambda at reverse.cpp:21:9>' vs. 'char')
operator+(_CharT __lhs, basic_string<_CharT,_Traits,_Allocator>&& __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/iterator:630:1: note:
      candidate template ignored: could not match 'reverse_iterator' against
      'basic_string'
operator+(typename reverse_iterator<_Iter>::difference_type __n, const r...
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/iterator:1025:1: note:
      candidate template ignored: could not match 'move_iterator' against
      'basic_string'
operator+(typename move_iterator<_Iter>::difference_type __n, const move...
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/iterator:1381:1: note:
      candidate template ignored: could not match '__wrap_iter' against
      'basic_string'
operator+(typename __wrap_iter<_Iter>::difference_type __n,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:3881:1: note:
      candidate template ignored: could not match
      'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>'
      against '<lambda at reverse.cpp:21:9>'
operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:3894:1: note:
      candidate template ignored: could not match 'const _CharT *' against
      '<lambda at reverse.cpp:21:9>'
operator+(const _CharT* __lhs , const basic_string<_CharT,_Traits,_Alloc...
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:3917:1: note:
      candidate template ignored: could not match
      'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>'
      against '<lambda at reverse.cpp:21:9>'
operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs, const ...
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:3929:1: note:
      candidate template ignored: could not match
      'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>'
      against '<lambda at reverse.cpp:21:9>'
operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs, _CharT __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:3943:1: note:
      candidate template ignored: could not match
      'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>'
      against '<lambda at reverse.cpp:21:9>'
operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, const basic...
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:3951:1: note:
      candidate template ignored: could not match
      'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>'
      against '<lambda at reverse.cpp:21:9>'
operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs, basic_...
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:3959:1: note:
      candidate template ignored: could not match
      'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>'
      against '<lambda at reverse.cpp:21:9>'
operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, basic_strin...
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:3967:1: note:
      candidate template ignored: could not match 'const _CharT *' against
      '<lambda at reverse.cpp:21:9>'
operator+(const _CharT* __lhs , basic_string<_CharT,_Traits,_Allocator>&& __rhs)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/string:3984:1: note:
      candidate template ignored: could not match
      'basic_string<type-parameter-0-0, type-parameter-0-1, type-parameter-0-2>'
      against '<lambda at reverse.cpp:21:9>'
operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, const _Char...