C++ named requirements: CharTraits
From cppreference.com
CharTraits is a traits class that abstracts basic character and string operations for a given character type. Most standard library string and input/output classes require a CharTraits template type parameter alongside a corresponding character template type parameter.
Requirements
No operation on CharTraits may throw an exception.
Given
- CharT, a character type
- X, a CharTraits type for type CharT
- c, d, values of type CharT
- p, q, values of type const CharT*
- s, a value of type CharT*
- n, i, j, values of type std::size_t
- e, f, values of type X::int_type
- pos, a value of type X::pos_type
- state, a value of type X::state_type
- r, an lvalue of type CharT
expression | return type | semantics | complexity |
---|---|---|---|
X::char_type | CharT | Used to refer to the character type | Compile-time |
X::int_type | A type that can hold all valid values of X::char_type plus X::eof() | Compile-time | |
X::off_type | Invokes implementation-defined behaviour if not std::streamoff when X is used as the traits template parameter in input/output classes. | Compile-time | |
X::pos_type |
|
Compile-time | |
X::state_type | Destructible, CopyAssignable, CopyConstructible, DefaultConstructible | Compile-time | |
X::eq(c,d) | bool | Returns: whether c is to be treated as equal to d | Constant |
X::lt(c,d) | bool | Returns: whether c is to be treated as less than d | Constant |
X::compare(p,q,n) | int | Returns:
|
Linear |
X::length(p) | std::size_t | Returns: the smallest i such that X::eq(p[i], CharT()) is true | Linear |
X::find(p,n,c) | const X::char_type* | Returns:
|
Linear |
X::move(s,p,n) | X::char_type* |
|
Linear |
X::copy(s,p,n) | X::char_type* |
|
Linear |
X::assign(r,d) | (Not used) | Assigns r = d | Constant |
X::assign(s,n,c) | X::char_type* |
|
Linear |
X::not_eof(e) | X::int_type | Returns:
|
Constant |
X::to_char_type(e) | X::char_type | Returns:
|
Constant |
X::to_int_type(c) | X::int_type | Returns: some value e, constrained by the definitions of X::to_char_type and X::eq_int_type | Constant |
X::eq_int_type(e,f) | bool |
|
Constant |
X::eof() | X::int_type | Returns: a value e such that X::eq_int_type(e, X::to_int_type(c)) is false for all values c | Constant |
Standard library
CharTraits is required by the following standard library class templates as a template type parameter:
stores and manipulates sequences of characters (class template) | |
(C++17) |
read-only string view (class template) |
manages an arbitrary stream buffer (class template) | |
wraps a given abstract device (std::basic_streambuf) and provides high-level input interface (class template) | |
implements high-level file stream input operations (class template) | |
implements high-level string stream input operations (class template) | |
wraps a given abstract device (std::basic_streambuf) and provides high-level output interface (class template) | |
implements high-level file stream output operations (class template) | |
implements high-level string stream output operations (class template) | |
(C++20) |
synchronized output stream wrapper (class template) |
wraps a given abstract device (std::basic_streambuf) and provides high-level input/output interface (class template) | |
implements high-level file stream input/output operations (class template) | |
implements high-level string stream input/output operations (class template) | |
input iterator that reads from std::basic_istream (class template) | |
output iterator that writes to std::basic_ostream (class template) | |
abstracts a raw device (class template) | |
implements raw file device (class template) | |
implements raw string device (class template) | |
(C++20) |
synchronized output device wrapper (class template) |
input iterator that reads from std::basic_streambuf (class template) | |
output iterator that writes to std::basic_streambuf (class template) |
CharTraits is satisfied by the following standard library classes:
template<> class char_traits<char>; template<> class char_traits<wchar_t>; |
(since C++20) (since C++11) (since C++11) |
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