std::ctype

From Cppreference

Jump to: navigation, search

Defined in header `<locale>`

template< class CharT > class ctype : public std::locale::facet, public std::ctype_base;

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.

Two specializations are provided by the standard library

Defined in header `<locale>`

`std::ctype<char>`	provides equivalents of the "C" locale classification. This specialization uses table lookup for character classification

std::ctype<wchar_t>	provides wide character equivalents of the "C" locale classification


(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)

[edit] Protected member functions


do_is [virtual]	classifies a character or a character sequence (virtual protected member function)

do_scan_id [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 givne 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)

[edit] Example

The following example demonstrates modification of a ctype other than ctype<char> to tokenize of 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 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);
    s2.imbue(std::locale(s2.getloc(), new csv_whitespace()));
    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

[edit] 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)


Member name	Type

`id` (static)	std::locale::id

std::ctype

From Cppreference

Contents

[edit] Member types

[edit] Member objects