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Standard Template Library Programmer's Guide
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char_traits


Category: utilities	Component type: type

Description

The char_traits class is the default Character Traits class used by the library; it is the only predefined Character Traits class.

Example

The char_traits class is of no use by itself. It is used as a template parameter of other classes, such as the basic_string template.

Definition

Defined in the standard header string.

Template parameters

Parameter	Description	Default
`charT`	`char_traits`'s value type, i.e. `char_traits<>::char_type`.

Model of

Character Traits

Type requirements

charT is either char or wchar_t.

(All of char_traits's member functions are defined for arbitrary types, but some of char_traits's members must be explicitly specialized if char_traits is to be useful for other types than char and wchar_t.

Public base classes

None.

Members

All of char_traits's members are static. There is never any reason to create an object of type char_traits.

Member	Where defined	Description
`char_type`	Character Traits	`char_traits`'s value type: `charT`.
`int_type`	Character Traits	`char_traits`'s int type.
`pos_type`	Character Traits	`char_traits`'s position type.
`off_type`	Character Traits	`char_traits`'s offset type
`state_type`	Character Traits	`char_traits`'s state type.
`static void assign(char_type& c1, const char_type& c2)`	Character Traits	Assigns `c2` to `c1`.
`static bool eq(const char_type& c1, const char_type& c2)`	Character Traits	Character equality.
`static bool lt(const char_type& c1, const char_type& c2)`	Character Traits	Returns `true` if `c1` is less than `c2`.
`static int compare(const char_type* p1, const char_type* p2, size_t n)`	Character Traits	Three-way lexicographical comparison, much like `strncmp`.
Length	`static size_t length(const char* p)`	Returns length of a null-terminated array of characters.
`static const char_type* find(const char_type* p, size_t n, const char_type& c)`	Character Traits	Finds `c` in `[p, p+n)`, returning 0 if not found.
`static char_type* move(char_type* s, const char_type* p, size_t n)`	Character Traits	Copies characters from `[p, p+n)` to the (possibly overlapping) range `[s, s+n)`.
`static char_type* copy(char_type* s, const char_type* p, size_t n)`	Character Traits	Copies characters from `[p, p+n)` to the (non-overlapping) range `[s, s+n)`.
`static char_type* assign(char_type* s, size_t n, char_type c)`	Character Traits	Assigns the value `c` to every element in the range `[s, s+n)`.
`static int_type eof()`	Character Traits	Returns the value used as an EOF indicator.
`static int_type not_eof(const int_type& c)`	Character Traits	Returns a value that is not equal to `eof()`. Returns `c` unless `c` is equal to `eof()`.
`static char_type to_char_type(const int_type& c)`	Character Traits	Returns the `char_type` value corresponding to `c`, if such a value exists.
`static int_type to_int_type(const char_type& c)`	Character Traits	Returns a `int_type` representation of `c`.
`static bool eq_int_type(cosnt int_type& c1, const int_type& c1)`	Character Traits	Tests whether two `int_type` values are equal. If the values can also be represented as `char_type`, then `eq` and `eq_int_type` must be consistent with each other.

New members

None. All of char_traits's members are defined in the Character Traits requirements.