std::ctype::scan_is(3)

🌸 std::ctype::scan_is 🌸

okay so bestie, this is the C++ Standard Libary manual page for std::ctype::scan_is(3) — yes the typo is in the original, we're keeping it, it's iconic. 💅

✨ 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)

it 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. that's an implementation-defined situation, so don't assume more than this page says. 🙈

🎀 Parameters 🎀

• m — the 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. periodt 💖

🧚 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, bestie:

// Run this code
#include <iostream>
#include <iterator>
#include <locale>

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; it's a virtual protected member function of std::ctype<CharT>.
• scan_not — locates the first character in a sequence that fails given classification, using the classification table; it's a public member function.

mwah 💋 — source: http://cppreference.com, version/date: 2024.06.10, page: std::ctype::scan_is(3). bye bestie 🫶