std::wcstol,std::wcstoll(3)

💖 NAME 💖

std::wcstol,std::wcstoll(3) — hi bestie 💖 welcome to the page from the C++ Standard Libary manual (yes, “Libary” is literally how the header spells it and we’re keeping the typo because it’s iconic 💅). This is all about std::wcstol and std::wcstoll, the wide-string-to-integer besties. periodt.

✨ Synopsis ✨

Defined in header <cwchar> — locked and loaded:

long      wcstol ( const wchar_t* str, wchar_t** str_end, int base );
long long wcstoll( const wchar_t* str, wchar_t** str_end, int base );

wcstoll is (since C++11).

Okay so these functions interpret an integer value in a wide string pointed to by str. They discard any whitespace characters (as identified by calling std::iswspace) until the first non-whitespace character is found, then take as many characters as possible to form a valid base-n (where n=base) integer number representation and convert them to an integer value. The valid integer value consists of the following parts:

• (optional) plus or minus sign
• (optional) prefix (0) indicating octal base (applies only when the base is 8 or 0)
• (optional) prefix (0x or 0X) indicating hexadecimal base (applies only when the base is 16 or 0)
• a sequence of digits

The set of valid values for base is {0,2,3,...,36}. The set of valid digits for base-2 integers is {0,1}, for base-3 integers is {0,1,2}, and so on. For bases larger than 10, valid digits include alphabetic characters, starting from Aa for base-11 integer, to Zz for base-36 integer. The case of the characters is ignored.

Additional numeric formats may be accepted by the currently installed C locale.

If the value of base is 0, the numeric base is auto-detected: if the prefix is 0, the base is octal, if the prefix is 0x or 0X, the base is hexadecimal, otherwise the base is decimal.

If the minus sign was part of the input sequence, the numeric value calculated from the sequence of digits is negated as if by unary minus in the result type.

The functions set the pointer pointed to by str_end to point to the wide character past the last character interpreted. If str_end is a null pointer, it is ignored.

🎀 Parameters 🎀

• str — pointer to the null-terminated wide string to be interpreted
• str_end — pointer to a pointer to wide character
• base — base of the interpreted integer value

🌈 Return value 🌈

Integer value corresponding to the contents of str on success. If the converted value falls out of range of corresponding return type, range error occurs and LONG_MAX, LONG_MIN, LLONG_MAX or LLONG_MIN is returned. If no conversion can be performed, 0 is returned.

💻 Example 💻

// Run this code

        #include <cwchar>
        #include <errno.h>
        #include <iostream>
        #include <string>

        int main()
        {
            const wchar_t* p = L"10 200000000000000000000000000000 30 -40";
            wchar_t* end;
            std::wcout << "Parsing L'" << p << "':\n";
            for (long i = std::wcstol(p, &end, 10); p != end; i = std::wcstol(p, &end, 10))
            {
                std::wcout << '\'' << std::wstring(p, end-p) << "' -> ";
                p = end;
                if (errno == ERANGE)
                {
                    std::wcout << "range error, got ";
                    errno = 0;
                }
                std::wcout << i << '\n';
            }
        }

🍓 Possible output 🍓

        Parsing L'10 200000000000000000000000000000 30 -40':
        '10' -> 10
        ' 200000000000000000000000000000' -> range error, got
       9223372036854775807
        ' 30' -> 30
        ' -40' -> -40

👑 See also 👑

• strtol — converts a byte string to an integer value
• strtoll — (function) (C++11)
• wcstoul — converts a wide string to an unsigned integer value
• wcstoull — (function)
• C documentation for wcstol, wcstoll

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source/version/date sign-off: http://cppreference.com · 2024.06.10 · mwah, bestie 💋✨