concat_str

concat_str is a utility function for concatenating multiple string types while minimizing potential free store allocations.

Illustration of the problem

Potentially multiple reallocations:

using namespace std::string_literals;
// Pretend this is concatenating dynamic strings from functions
auto const s = "Hello world!"s + ' ' + "This is C++."s + ' ' + "Here is a string.";

Instead use a function that will calculate the total length and reserve the string memory once:

// Pretend this is concatenating dynamic strings from functions
auto const s = zpp::concat_string("Hello world!", ' ', "This is C++.", ' ', "Here is a string.");

API

Main convenience functions:

• std::string concat_string(...)
• std::wstring concat_wstring(...)
• std::u8string concat_u8string(...) (requires C++20)
• std::u16string concat_u16string(...)
• std::u32string concat_u32string(...)

Generic template function:

• template <typename CharT, typename Traits, typename Alloc, typename... Ts>
  std::basic_string<CharT, Traits, Alloc> concat_basic_string(...)

Supported types

Requires that the underlying character types are all the same. I.e., no mixing char and wchar_t.

• Single character
  • char
  • wchar_t
  • char8_t (requires C++20)
  • char16_t
  • char32_t
• String literal
  • ""
  • L""
  • u8""
  • u""
  • U""
• std::basic_string<...>
  • std::string
  • std::wstring
  • std::u8string (requires C++20)
  • std::u16string
  • std::u32string
• std::basic_string_view<...> (requires C++17)
  • std::string_view (requires C++17)
  • std::wstring_view (requires C++17)
  • std::u8string_view (requires C++20)
  • std::u16string_view (requires C++17)
  • std::u32string_view (requires C++17)
• std::initializer_list<CharT>

Requirements

C++11 with variadic template support