std::ctype

Defined in header `<locale>`
template< class CharT > class ctype;

Class ctype encapsulates character classification features. All stream input operations performed through std::basic_istream<CharT> use the std::ctype<CharT> of the locale imbued in the stream to identify whitespace characters for input tokenization. Stream output operations apply std::ctype<CharT>::widen() to narrow-character arguments prior to output.

Inheritance diagram

Specializations

The standard library is guaranteed to provide the following specializations (they are required to be implemented by any locale object):

Defined in header `<locale>`
`std::ctype<char>`	provides narrow character equivalents of the minimal "C" locale classification. This specialization uses table lookup for character classification
std::ctype<wchar_t>	provides wide character classification appropriate to the native character set

Nested types

Type	Definition
`char_type`	`CharT`

Data members

Member	Description
`std::locale::id` `id` [static]	the identifier of the facet

Member functions

(constructor)	constructs a new `ctype` facet (public member function)
(destructor)	destructs a `ctype` facet (protected member function)
is	invokes `do_is` (public member function)
scan_is	invokes `do_scan_is` (public member function)
scan_not	invokes `do_scan_not` (public member function)
toupper	invokes `do_toupper` (public member function)
tolower	invokes `do_tolower` (public member function)
widen	invokes `do_widen` (public member function)
narrow	invokes `do_narrow` (public member function)

Protected member functions

do_is [virtual]	classifies a character or a character sequence (virtual protected member function)
do_scan_is [virtual]	locates the first character in a sequence that conforms to given classification (virtual protected member function)
do_scan_not [virtual]	locates the first character in a sequence that fails given classification (virtual protected member function)
do_toupper [virtual]	converts a character or characters to uppercase (virtual protected member function)
do_tolower [virtual]	converts a character or characters to lowercase (virtual protected member function)
do_widen [virtual]	converts a character or characters from char to `CharT` (virtual protected member function)
do_narrow [virtual]	converts a character or characters from `CharT` to char (virtual protected member function)

Inherited from std::ctype_base

Nested types

Type	Definition
`mask`	unspecified BitmaskType type (enumeration, integer type, or bitset)

Member constants

space [static]	the value of `mask` identifying whitespace character classification (public static member constant)
print [static]	the value of `mask` identifying printable character classification (public static member constant)
cntrl [static]	the value of `mask` identifying control character classification (public static member constant)
upper [static]	the value of `mask` identifying uppercase character classification (public static member constant)
lower [static]	the value of `mask` identifying lowercase character classification (public static member constant)
alpha [static]	the value of `mask` identifying alphabetic character classification (public static member constant)
digit [static]	the value of `mask` identifying digit character classification (public static member constant)
punct [static]	the value of `mask` identifying punctuation character classification (public static member constant)
xdigit [static]	the value of `mask` identifying hexadecimal digit character classification (public static member constant)
blank [static] (C++11)	the value of `mask` identifying blank character classification (public static member constant)
alnum [static]	`alpha \| digit` (public static member constant)
graph [static]	`alnum \| punct` (public static member constant)

Example

The following example demonstrates modification of a ctype other than ctype<char> to tokenize a CSV file:

#include <iostream>
#include <locale>
#include <sstream>
 
struct csv_whitespace : std::ctype<wchar_t>
{
    bool do_is(mask m, char_type c) const
    {
        if ((m & space) && c == L' ')
            return false; // space will NOT be classified as whitespace
        
        if ((m & space) && c == L',')
            return true; // comma will be classified as whitespace
        
        return ctype::do_is(m, c); // leave the rest to the base class
    }
};
 
int main()
{
    std::wstring in = L"Column 1,Column 2,Column 3\n123,456,789";
    std::wstring token;
    
    std::wcout << "default locale:\n";
    std::wistringstream s1(in);
    while (s1 >> token)
        std::wcout << "  " << token << '\n';
    
    std::wcout << "locale with modified ctype:\n";
    std::wistringstream s2(in);
    csv_whitespace* my_ws = new csv_whitespace;
    s2.imbue(std::locale(s2.getloc(), my_ws));
    while (s2 >> token)
        std::wcout << "  " << token << '\n';
}

Output:

default locale:
  Column
  1,Column
  2,Column
  3
  123,456,789
locale with modified ctype:
  Column 1
  Column 2
  Column 3
  123
  456
  789

ctype<char>	specialization of `std::ctype` for type char (class template specialization)
ctype_base	defines character classification categories (class)
ctype_byname	represents the system-supplied `std::ctype` for the named locale (class template)

std::ctype

Specializations

Nested types

Data members

Member functions

Protected member functions

Inherited from std::ctype_base

Nested types

Member constants

Example

See also