std::ctype

locale::facet		ctype
ctype_base

The ctype standard facet is used to classify and convert characters.

ctype objects are prevented to be locally constructed by having a protected destructor. Only those installed in locale objects should be used through mechanisms such as use_facet.

This template class has one template parameter, representing the character type with which the facet works. This template parameter is referred in this entire reference as charT.

Public members

It includes the following 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)

It also declares the following alias type:

char_type

Internal character type (public member type)

And inherits the following type:

mask

Character category bitmask type (public member type)

Virtual protected members

The class defines the virtual protected members in charge of implementing the expected behavior 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)

ctype specialization: ctype<char>

The char version is specialized, so that some of their member functions can be implemented inline instead of calling their do_ counterpart (this is the case for members is, scan_is and scan_not).

The constructor for this specialization is different than the one for the general template (see ctype::ctype for more info).

This specialization keeps an internal table array member. This private member is an array of elements of type ctype::mask containing 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. In other words, the table is what member ctype::is would return for an array of char elements whose values are the sequence of values a char element can take, from 0 to its highest value.

The highest value in the table is given by public member constant ctype::table_size (which is, at least, 256).

Also, two additional protected members are provided in this specialization to access the table:

const mask* table () const throw;

Returns the table being used by the object. This is either the first argument used in the constructor, or the classic table if zero was used as first argument for the constructor.

static const mask* classic_table () throw;

Returns the classic table, which is a default table used in case none is provided in the constructor.