Difference between revisions of "cpp/string/wide/wcstoimax"

Revision as of 12:05, 10 April 2013

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Interprets an unsigned integer value in a wide string pointed to by nptr.

Discards any whitespace characters (as identified by calling std::isspace) until the first non-whitespace character is found, then takes as many characters as possible to form a valid base-n (where n=base) unsigned integer number representation and converts them to an integer value. The valid unsigned 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, which applies unsigned integer wraparound rules.

The functions sets the pointer pointed to by endptr to point to the wide character past the last character interpreted. If endptr is NULL, it is ignored.

Parameters

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 INTMAX_MAX, INTMAX_MIN, UINTMAX_MAX, or ​0​ is returned, as appropriate. If no conversion can be performed, ​0​ is returned.

Example

#include <iostream>
#include <string>
#include <cinttypes>
 
int main()
{
    std::wstring str = L"helloworld";
    std::intmax_t val = std::wcstoimax(str.c_str(), nullptr, 36);
    std::wcout << str << " in base 36 is " << val << " in base 10\n";
 
    wchar_t* nptr;
    val = std::wcstoimax(str.c_str(), &nptr, 30);
    if(nptr != &str[0] + str.size())
        std::wcout << str << " in base 30 is invalid."
                  << " The first invalid digit is " << *nptr << '\n';
}

helloworld in base 36 is 1767707668033969 in base 10
helloworld in base 30 is invalid. The first invalid digit is w

See also