std::filesystem::path::concat,std::filesystem::path::operator+=(3)

NAME
std::filesystem::path::concat,std::filesystem::path::operator+= - std::filesystem::path::concat,std::filesystem::path::operator+=

Synopsis
   path& operator+=( const path& p ); (1) (since C++17)
   path& operator+=( const string_type& str ); (2) (since C++17)
   path& operator+=( std::basic_string_view<value_type> str );
   path& operator+=( const value_type* ptr ); (3) (since C++17)
   path& operator+=( value_type x ); (4) (since C++17)
   template< class CharT > (5) (since C++17)
   path& operator+=( CharT x );
   template< class Source > (6) (since C++17)
   path& operator+=( const Source& source );
   template< class Source > (7) (since C++17)
   path& concat( const Source& source );
   template< class InputIt > (8) (since C++17)
   path& concat( InputIt first, InputIt last );
   Concatenates the current path and the argument
   1-3,6,7) Appends path(p).native() to the pathname stored in *this in the native
   format. This directly manipulates the value of native() and may not be portable
   between operating systems.
   4,5) Same as return *this += std::basic_string_view(&x, 1);.
   8) Same as return *this += path(first, last);.
   (6) and (7) participate in overload resolution only if Source and path are not the
   same type, and either:
     * Source is a specialization of std::basic_string or std::basic_string_view, or
     * std::iterator_traits<std::decay_t<Source>>::value_type is valid and denotes a
       possibly const-qualified encoding character type (char,
       char8_t,
       (since C++20)char16_t, char32_t, or wchar_t).

Parameters
   p - path to append
   str - string or string view to append
   ptr - pointer to the beginning of a null-terminated string to append
   x - single character to append
                  std::basic_string, std::basic_string_view, null-terminated
   source - multicharacter string, or an input iterator pointing to a
                  null-terminated multicharacter sequence, which represents a path name
                  (either in portable or in native format)
   first, last - pair of LegacyInputIterators that specify a multicharacter sequence
                  that represents a path name

Type requirements
   -
   InputIt must meet the requirements of LegacyInputIterator.
   -
   The value type of InputIt must be one of the encoded character types (char, wchar_t,
   char16_t and char32_t).
   -
   CharT must be one of the encoded character types (char, wchar_t, char16_t and
   char32_t).

Return value
   *this

Exceptions
   May throw std::bad_alloc if memory allocation fails.

Notes
   Unlike with append() or operator/=, additional directory separators are never
   introduced.

Example
// Run this code
 #include <filesystem>
 #include <iostream>
 #include <string>
 int main()
 {
     std::filesystem::path p1; // an empty path
     p1 += "var"; // does not insert a separator
     std::cout << R"("" + "var" --> )" << p1 << '\n';
     p1 += "lib"; // does not insert a separator
     std::cout << R"("var" + "lib" --> )" << p1 << '\n';
     auto str = std::string{"1234567"};
     p1.concat(std::begin(str) + 3, std::end(str) - 1);
     std::cout << "p1.concat --> " << p1 << '\n';
 }

Output:
 "" + "var" --> "var"
 "var" + "lib" --> "varlib"
 p1.concat --> "varlib456"
   Defect reports
   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.
      DR Applied to Behavior as published Correct behavior
   LWG 3055 C++17 the specification of concatenating a single made well-formed
                       character was ill-formed
   LWG 3244 C++17 constraint that Source cannot be path was added
                       missing

See also
   append appends elements to the path with a directory separator
   operator/= (public member function)
   operator/ concatenates two paths with a directory separator
   (C++17) (function)