template< class CharT >
class ctype;
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
[edit] SpecializationsThe standard library is guaranteed to provide the following specializations (they are required to be implemented by any locale object):
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 [edit] Nested types Type Definition char_type CharT [edit] Data members [edit] Member functions [edit] Protected member functions classifies a character or a character sequence
CharT
CharT to char
mask unspecified BitmaskType type (enumeration, integer type, or bitset) Member constants the value of mask identifying whitespace character classification
mask identifying printable character classification
mask identifying control character classification
mask identifying uppercase character classification
mask identifying lowercase character classification
mask identifying alphabetic character classification
mask identifying digit character classification
mask identifying punctuation character classification
mask identifying hexadecimal digit character classification
mask identifying blank character classification
The following example demonstrates modification of a ctype other than ctype<char> to tokenize 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 base 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[edit] See also specialization of std::ctype for type char
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