std::ctype<char>::scan_is (3) - Linux Manuals

std::ctype<char>::scan_is: std::ctype<char>::scan_is


std::ctype<char>::scan_is - std::ctype<char>::scan_is


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.


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.


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.


// 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";



See also

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