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std::ctype<CharT>::scan_is, std::ctype<CharT>::do_scan_is

Defined in header <locale> 
public:
const CharT* scan_is( mask m, const CharT* beg, const CharT* end ) const;
 (1) 
protected:
virtual const CharT* do_scan_is( mask m, const CharT* beg, const CharT* end ) const;
 (2)
1) public member function, calls the protected virtual member function do_scan_is of the most derived class.
2) Locates the first character in the character array [beg, end) that satisfies the classification mask m, that is, the first character c such that is(m, c) would return true.

Parameters

m - mask to search for
beg - pointer to the first character in an array of characters to search
end - one past the end pointer for the array of characters to search

Return value

Pointer to the first character in [beg, end) that satisfies the mask, or end if no such character was found.

Example

#include <locale>
#include <clocale>
#include <iostream>
#include <iterator>
 
int main()
{
    std::setlocale(LC_ALL, "en_US.utf8");
    std::wcout.imbue(std::locale("en_US.utf8"));
    auto& f = std::use_facet<std::ctype<wchar_t>>(std::wcout.getloc());
 
    // skip until the first letter
    wchar_t s1[] = L"      \t\t\n  Кошка";
    const wchar_t* p1 = f.scan_is(std::ctype_base::alpha, std::begin(s1), std::end(s1));
    std::wcout << "'" << p1 << "'\n";
 
    // skip until the first letter
    wchar_t s2[] = L"123456789ネプネプ";
    const wchar_t* p2 = f.scan_is(std::ctype_base::alpha, std::begin(s2), std::end(s2));
    std::wcout << "'" << p2 << "'\n";
}

Output:

'Кошка'
'ネプネプ'

Defect reports

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

DR Applied to Behavior as published Correct behavior
LWG 152 C++98 the effect of do_scan_is mentioned is(m),
but is does not have such an overload 		corrected to is(m, c)

See also

locates the first character in a sequence that conforms to given classification, using the classification table
(public member function of std::ctype<char>)
[virtual]
 locates the first character in a sequence that fails given classification
(virtual protected member function)

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