NAME¶

std::ctype::scan_is - std::ctype::scan_is

Synopsis¶

Defined in header <locale>
const char* scan_is (mask m, const char* beg, const char* end) const; (1)

Locates the first character in the character array [beg, end) that satisfies the
classification mask m, that is, the first character c such that table()[(unsigned
char) c] & m would return true.

If (unsigned char)c >= std::ctype<char>::table_size, then an implementation-defined
value is substituted instead of table()[(unsigned char)c], possibly different for
different values of c.

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.

Notes¶

Unlike the primary template std::ctype, this specialization does not perform a
virtual function call when classifying characters. To customize the behavior, a
derived class may provide a non-default classification table to the base class
constructor.

Example¶

// Run this code

#include <locale>
#include <iostream>
#include <iterator>

int main()
{
std::locale loc("");
auto& f = std::use_facet<std::ctype<char>>(loc);

// skip until the first letter
char s1[] = " \t\t\n Test";
const char* p1 = f.scan_is(std::ctype_base::alpha, std::begin(s1), std::end(s1));
std::cout << "'" << p1 << "'\n";

// skip until the first letter
char s2[] = "123456789abcd";
const char* p2 = f.scan_is(std::ctype_base::alpha, std::begin(s2), std::end(s2));
std::cout << "'" << p2 << "'\n";
}

Output:¶

'Test'
'abcd'

See also¶

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