class template

std::ctype

template <class charT> class ctype;

Character type facet

locale::facet ctype_base
ctype

The ctype standard facet classifies and transforms characters, adapting the functionality of the C library header <cctype> to C++ locales.

The ctype class template has a protected destructor: Programs shall only construct objects of derived classes, or use those installed in locale objects (through use_facet ).

All standard locale objects support at least the following facet instantiations of the ctype class template as part of the ctype category:

facets in `locale` objects	description
`ctype<char>`	narrow characters produces the same results as the functions in header `<cctype>` for the classic locale * specialized with a particular implementation (see specializations below)
`ctype<wchar_t>`	wide characters

Template parameters

charT: Character type.
Aliased as member char_type.

Member types

member type	definition	description
`char_type`	The template parameter (`charT`)	Character type

The class also inherits ctype_base::mask , which is used extensively as a parameter and return type by member functions (see ctype_base ).

Member constants

The following member constants are inherited from ctype_base ; They are used to identify character categories.

member constant	type	value	description
`space`	`ctype_base::mask`	unspecified (unique bits)	white-space character
`print`	`ctype_base::mask`	unspecified (unique bits)	printable character
`cntrl`	`ctype_base::mask`	unspecified (unique bits)	control character
`upper`	`ctype_base::mask`	unspecified (unique bits)	uppercase letter
`lower`	`ctype_base::mask`	unspecified (unique bits)	lowercase letter
`alpha`	`ctype_base::mask`	unspecified (unique bits)	alphabetic character
`digit`	`ctype_base::mask`	unspecified (unique bits)	decimal digit
`punct`	`ctype_base::mask`	unspecified (unique bits)	punctuation character
`xdigit`	`ctype_base::mask`	unspecified (unique bits)	hexadecimal digit
`alnum`	`ctype_base::mask`	`alpha\|digit`	alpha-numeric character
`graph`	`ctype_base::mask`	`alnum\|punct`	character with graphic representation

member constant	type	value	description
`space`	`ctype_base::mask`	unspecified (unique bits)	white-space character
`print`	`ctype_base::mask`	unspecified (unique bits)	printable character
`cntrl`	`ctype_base::mask`	unspecified (unique bits)	control character
`upper`	`ctype_base::mask`	unspecified (unique bits)	uppercase letter
`lower`	`ctype_base::mask`	unspecified (unique bits)	lowercase letter
`alpha`	`ctype_base::mask`	unspecified (unique bits)	alphabetic character
`digit`	`ctype_base::mask`	unspecified (unique bits)	decimal digit
`punct`	`ctype_base::mask`	unspecified (unique bits)	punctuation character
`xdigit`	`ctype_base::mask`	unspecified (unique bits)	hexadecimal digit
`blank`	`ctype_base::mask`	unspecified (unique bits)	blank character
`alnum`	`ctype_base::mask`	`alpha\|digit`	alpha-numeric character
`graph`	`ctype_base::mask`	`alnum\|punct`	character with graphic representation

See <cctype> for details on how ASCII characters are classified with respect to these categories.

The class also contains a public static constant of type locale::id , that uniquely identifies facets with ctype semantics.

Public member functions

(constructor): ctype constructor (public member function)

Character classification

is: Classify characters (public member function)

scan_is: Return first character in category (public member function)

scan_not: Return first character not in category (public member function)

Character transformation

toupper: Convert to uppercase (public member function)

tolower: Convert to lowercase (public member function)

widen: Widen character(s) (public member function)

narrow: Narrow character(s) (public member function)

Virtual protected member functions

The class defines the virtual protected members which implement the behavior by default of their respective public member functions:

do_is: Classify characters [virtual] (protected virtual member function)

do_scan_is: Return first character in category [virtual] (protected virtual member function)

do_scan_not: Return first character not in category [virtual] (protected virtual member function)

do_toupper: Convert to uppercase [virtual] (protected virtual member function)

do_tolower: Convert to lowercase [virtual] (protected virtual member function)

do_widen: Widen character(s) [virtual] (protected virtual member function)

do_narrow: Narrow character(s) [virtual] (protected virtual member function)

Along with the class destructor:

(destructor): ctype destructor (protected member function)

Specializations

At least the following specializations of this template are provided in all library implementations:

specialization
`ctype<char>`
`ctype<wchar_t>`

Particular specialization: `ctype<char>`

On the char specialization, some of the member functions are implemented inline instead of calling their do_ counterparts (this is the case for members is , scan_is and scan_not ).

It has a different constructor, and keeps an internal table of elements of type ctype::mask with the classification of each of the characters in the character set: The value of each element in the array corresponds to the classification of the character given by its order position.

The size of this table is indicated by an additional static public member constant:

member constant	type	value	description
`table_size`	`const size_t`	implementation-specific (at least `256`)	The size of the `table`

This specialization contains two additional protected members:

table: Get category table (public member function)

classic_table: Get classic table (public static member function)

This specialization contains two additional public members:

table: Get category table (public member function)

classic_table: Get classic table (public static member function)

Note that do_is , do_scan_is and do_scan_not are not members of the char specialization.

functions

standard facets

public member functions

ctype<char> specialization

protected members