concat_string's Introduction

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>