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# std::ctype<char>::scan_is

From cppreference.com
< cpp‎ | locale‎ | ctype char

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.

### [edit] 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

### [edit] Return value

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

### [edit] 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.

### [edit] Example

Run this code

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

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

        // 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'

### [edit] See also

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

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