std::ctype - cppreference.com (original) (raw)

| | | | | ------------------------------ | | | | 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

Contents

• 1 Nested types
• 2 Data members
• 3 Member functions
• 4 Protected member functions
• 5 Inherited from std::ctype_base
  • 5.1 Nested types
  • 5.2 Member constants
  • 5.3 Example
  • 5.4 Defect reports
  • 5.5 See also

[edit] Nested types

[edit] Data members

[edit] Member functions

[edit] Protected member functions

| | converts a character or characters to uppercase (virtual protected member function of std::ctype) [edit] | | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | converts a character or characters to lowercase (virtual protected member function of std::ctype) [edit] | | | converts a character or characters from char to CharT (virtual protected member function of std::ctype) [edit] | | | converts a character or characters from CharT to char (virtual protected member function of std::ctype) [edit] |

Inherited from std::ctype_base

Nested types

Member constants

[edit] Example

The following example demonstrates modification of ctype<char> to tokenize comma-separated values:

#include #include #include #include #include   // This ctype facet classifies commas and endlines as whitespace struct csv_whitespace : std::ctype { static const mask* make_table() { // make a copy of the "C" locale table static std::vector 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] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also