std::ctype

 

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Technical Specifications

 

Localizations library

Locales and facets
locale
use_facet	has_facet
Character classification
isspace isblank (C++11) iscntrl isupper islower isalpha	isdigit ispunct isxdigit isalnum isprint isgraph
Conversions
toupper tolower	wstring_convert (C++11) wbuffer_convert (C++11)
Facet category base classes
ctype_base codecvt_base messages_base	time_base money_base
Facet categories
ctype ctype<char> codecvt collate messages time_get time_put	num_get num_put numpunct money_get money_put moneypunct
Locale-specific facets
ctype_byname codecvt_byname messages_byname collate_byname	time_get_byname time_put_byname numpunct_byname moneypunct_byname
Code conversion facets
codecvt_utf8 (C++11) codecvt_utf16 (C++11)	codecvt_utf8_utf16 (C++11) codecvt_mode (C++11)
C locale
setlocale localeconv lconv	LC_ALLLC_COLLATELC_CTYPELC_MONETARYLC_NUMERICLC_TIME

 

std::ctype

Member functions

ctype::ctype

ctype::~ctype

ctype::isctype::do_is

ctype::scan_isctype::do_scan_is

ctype::scan_notctype::do_scan_not

ctype::toupperctype::do_toupper

ctype::tolowerctype::do_tolower

ctype::widenctype::do_widen

ctype::narrowctype::do_narrow

Member functions of ctype<char>

ctype<char>::ctype

ctype<char>::~ctype

ctype<char>::table

ctype<char>::classic_table

ctype<char>::is

ctype<char>::scan_is

ctype<char>::scan_not

 

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

Two standalone (locale-independent) specializations are provided by the standard library:

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

In addition, every locale object constructed in a C++ program implements its own (locale-specific) versions of these specializations.

Member types

Member type	Definition
char_type	CharT

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)

Member objects

static std::locale::id id

id of the locale (public member object)

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

Member types

Type	Definition
mask	unspecified bitmask 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

Run this code

#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 parent 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; // note: this allocation is not leaked
    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

See also

ctype<char>	specialization of std::ctype for type char (class template specialization)
ctype_base	defines character classification categories (class template)
ctype_byname	creates a ctype facet for the named locale (class template)