std::char_traits<CharT>::to_char_type

From cppreference.com
< cpp‎ | string‎ | char traits
static char_type to_char_type( int_type c );
(until C++11)
static constexpr char_type to_char_type( int_type c ) noexcept;
(since C++11)

Converts a value of int_type to char_type. If there are no equivalent value (such as when c is a copy of the eof() value), the result is unspecified.

Formally, returns the value x such that X::eq_int_type(c, X::to_int_type(x)) is true, and an unspecified value if no such x exists.

Parameters

c - value to convert

Return value

A value equivalent to c.

Complexity

Constant.