Defined in header <locale> | ||
---|---|---|
template<> class ctype<char>; |
This specialization of std::ctype
encapsulates character classification features for type char
. Unlike general-purpose std::ctype
, which uses virtual functions, this specialization uses table lookup to classify characters (which is generally faster).
The base class std::ctype<char>
implements character classification equivalent to the minimal "C" locale. The classification rules can be extended or modified if constructed with a non-default classification table argument, if constructed as std::ctype_byname<char>
or as a user-defined derived facet. All std::istream
formatted input functions are required to use std::ctype<char>
for character classing during input parsing.
Inheritance diagram.
Member types
Member type | Definition |
---|---|
char_type | char |
Member functions
constructs a new std::ctype<char> facet (public member function) | |
(destructor)
| destructs a std::ctype<char> facet (protected member function) |
obtains the character classification table (public member function) | |
[static] | obtains the "C" locale character classification table (public static member function) |
classifies a character or a character sequence, using the classification table (public member function) | |
locates the first character in a sequence that conforms to given classification, using the classification table (public member function) | |
locates the first character in a sequence that fails given classification, using the classification table (public member function) | |
invokes do_toupper (public member function of std::ctype ) | |
invokes do_tolower (public member function of std::ctype ) | |
invokes do_widen (public member function of std::ctype ) | |
invokes do_narrow (public member function of std::ctype ) |
Protected member functions
[virtual] | converts a character or characters to uppercase (virtual protected member function of std::ctype ) |
[virtual] | converts a character or characters to lowercase (virtual protected member function of std::ctype ) |
[virtual] | converts a character or characters from char to charT (virtual protected member function of std::ctype ) |
[virtual] | converts a character or characters from charT to char (virtual protected member function of std::ctype ) |
Member objects
static std::locale::id id [static] | id of the locale (public static member constant) |
static const std::size_t table_size [static] | size of the classification table, at least 256 (public static member constant) |
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 ctype<char> to tokenize comma-separated values.
#include <iostream> #include <vector> #include <locale> #include <sstream> // This ctype facet classifies commas and endlines as whitespace struct csv_whitespace : std::ctype<char> { static const mask* make_table() { // make a copy of the "C" locale table static std::vector<mask> v(classic_table(), classic_table() + table_size); v[','] |= space; // comma will be classified as whitespace v[' '] &= ~space; // space will not be classified as whitespace return &v[0]; } csv_whitespace(std::size_t refs = 0) : ctype(make_table(), false, refs) {} }; int main() { std::string in = "Column 1,Column 2,Column 3\n123,456,789"; std::string token; std::cout << "default locale:\n"; std::istringstream s1(in); while(s1 >> token) std::cout << " " << token << '\n'; std::cout << "locale with modified ctype:\n"; std::istringstream s2(in); s2.imbue(std::locale(s2.getloc(), new csv_whitespace)); while(s2 >> token) std::cout << " " << 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
defines character classification tables (class template) | |
defines character classification categories (class template) | |
creates a ctype facet for the named locale (class template) |
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