std::char_traits::eq, std::char_traits::lt

From cppreference.com
static bool eq( char_type a, char_type b );
(1) (until C++11)
static constexpr bool eq( char_type a, char_type b ) noexcept;
(1) (since C++11)
static bool lt( char_type a, char_type b );
(2) (until C++11)
static constexpr bool lt( char_type a, char_type b ) noexcept;
(2) (since C++11)

Compares two characters.

1) Compares a and b for equality.
2) Compares a and b in such a way that they are totally ordered.

Contents

[edit] Parameters

a, b - character values to compare

[edit] Return value

1) true if a and b are equal, false otherwise.
2) true if a is less than b, false otherwise.

[edit] Exceptions

noexcept specification:  
noexcept
  (since C++11)

[edit] Complexity

Constant.