std::ctype
From cppreference.com
| Defined in header <locale>
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| template< class CharT > class ctype; |
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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
| constructs a new ctype facet (public member function) | |
| destructs a ctype facet (protected member function) | |
invokes do_is (public member function) | |
invokes do_scan_is (public member function) | |
invokes do_scan_not (public member function) | |
invokes do_toupper (public member function) | |
invokes do_tolower (public member function) | |
invokes do_widen (public member function) | |
invokes do_narrow (public member function) |
Member objects
| static std::locale::id id |
id of the locale (public member object) |
Protected member functions
| [virtual] |
classifies a character or a character sequence (virtual protected member function) |
| [virtual] |
locates the first character in a sequence that conforms to given classification (virtual protected member function) |
| [virtual] |
locates the first character in a sequence that fails given classification (virtual protected member function) |
| [virtual] |
converts a character or characters to uppercase (virtual protected member function) |
| [virtual] |
converts a character or characters to lowercase (virtual protected member function) |
| [virtual] |
converts a character or characters from char to charT (virtual protected member function) |
| [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; 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
| specialization of std::ctype for type char (class template specialization) | |
| defines character classification categories (class template) | |
| creates a ctype facet for the named locale (class template) |