std::ctype<char>
Defined in header
<locale>
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template<>
class ctype<char>; |
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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.
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[edit] Member types
Member type | Definition |
char_type
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char
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[edit] Member functions
constructs a new std::ctype<char> facet (public member function) |
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destructs a std::ctype<char> facet (protected member function) |
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obtains the character classification table (public member function) |
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[static]
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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) |
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locates the first character in a sequence that conforms to given classification, using the classification table (public member function) |
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locates the first character in a sequence that fails given classification, using the classification table (public member function) |
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invokes do_toupper (public member function of std::ctype )
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invokes do_tolower (public member function of std::ctype )
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invokes do_widen (public member function of std::ctype )
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invokes do_narrow (public member function of std::ctype )
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[edit] Protected member functions
[virtual]
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converts a character or characters to uppercase (virtual protected member function of std::ctype )
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[virtual]
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converts a character or characters to lowercase (virtual protected member function of std::ctype )
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[virtual]
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converts a character or characters from char to charT (virtual protected member function of std::ctype )
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[virtual]
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converts a character or characters from charT to char (virtual protected member function of std::ctype )
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[edit] Member objects
static std::locale::id id
[static]
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id of the locale (public static member constant) |
static const std::size_t table_size
[static]
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size of the classification table, at least 256 (public static member constant) |
Inherited from std::ctype_base
Member types
Type | Definition |
mask
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unspecified bitmask type (enumeration, integer type, or bitset) |
Member constants
space
[static]
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the value of mask identifying whitespace character classification (public static member constant) |
print
[static]
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the value of mask identifying printable character classification (public static member constant) |
cntrl
[static]
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the value of mask identifying control character classification (public static member constant) |
upper
[static]
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the value of mask identifying uppercase character classification (public static member constant) |
lower
[static]
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the value of mask identifying lowercase character classification (public static member constant) |
alpha
[static]
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the value of mask identifying alphabetic character classification (public static member constant) |
digit
[static]
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the value of mask identifying digit character classification (public static member constant) |
punct
[static]
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the value of mask identifying punctuation character classification (public static member constant) |
xdigit
[static]
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the value of mask identifying hexadecimal digit character classification (public static member constant) |
blank
[static] (C++11)
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the value of mask identifying blank character classification (public static member constant) |
alnum
[static]
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alpha | digit (public static member constant) |
graph
[static]
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alnum | punct (public static member constant) |
[edit] 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
[edit] See also
defines character classification tables (class template) |
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defines character classification categories (class template) |
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creates a ctype facet for the named locale (class template) |