std::char_traits::eq/lt, std::char_traits::eq/lt, std::char_traits::eq/lt, std::char_traits::eq/lt, std::char_traits::eq/lt (original) (raw)
| static bool eq( char_type a, char_type b ); | (1) | (constexpr since C++11)(noexcept since C++11) |
|---|---|---|
| static bool lt( char_type a, char_type b ); | (2) | (constexpr since C++11)(noexcept since C++11) |
Compares two characters.
- Compares a and b for equality, behaves identically to
- static_cast<unsigned char>(a) == static_cast<unsigned char>(b), if
char_typeis char, - a == b otherwise.
- Compares a and b in such a way that they are totally ordered, behaves identically to
- static_cast<unsigned char>(a) < static_cast<unsigned char>(b), if
char_typeis char, - a < b otherwise.
See CharTraits for the general requirements on character traits for X::eq and X::lt.
[edit] Parameters
| a, b | - | character values to compare |
|---|
[edit] Return value
true if a and b are equal, false otherwise.
true if a is less than b, false otherwise.
[edit] Complexity
Constant.
[edit] 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 467 | C++98 | for std::char_traits<char>, the semantics of eq() and lt()are the same as the built-in == and < on char respectively[1] | changed to built-in == and< on unsigned char |
- ↑ Most implementations call std::memcmp() for efficiency, which interprets the data as arrays of unsigned char. If char is signed on such implementations, std::char_traits<char> fails to satisfy the requirements of CharTraits.