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# std::strtoimax, std::strtoumax

From cppreference.com
< cpp‎ | string‎ | byte

Defined in header `<cinttypes>` |  |
std::intmax_t strtoimax( const char* nptr, char** endptr, int base ); |  | (since C++11)
std::uintmax_t strtoumax( const char* nptr, char** endptr, int base ); |  | (since C++11)

Interprets an integer value in a byte string pointed to by `nptr`.

Function discards any whitespace characters (as identified by calling `isspace()`) until first non-whitespace character is found. Then it takes as many characters as possible to form a valid base-n (where n=base) integer number representation and converts 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 digits for base-2 integer is `01`, for base-3 integer is `012`, 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.

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

If the `nptr` is empty or does not have the expected form, no conversion is performed, and (if `enptr` is not NULL) the value of `nptr` is stored in the object pointed to by `endptr`.

### [edit] Parameters

nptr | - | pointer to the null-terminated byte string to be interpreted
endptr | - | pointer to a pointer to character.
base | - | base of the interpreted integer value

### [edit] Return value

- If successful, an integer value corresponding to the contents of `str` is returned.
- If the converted value falls out of range of corresponding return type, a range error occurs (setting errno to ERANGE) and INTMAX_MAX, INTMAX_MIN, UINTMAX_MAX or ​0​ is returned, as appropriate.
- If no conversion can be performed, ​0​ is returned.

### [edit] Example

Run this code

    #include <iostream>
    #include <string>
    #include <cinttypes>

    int main()
    {
        std::string str = "helloworld";
        std::intmax_t val = std::strtoimax(str.c_str(), nullptr, 36);
        std::cout << str << " in base 36 is " << val << " in base 10\n";

        char* nptr;
        val = std::strtoimax(str.c_str(), &nptr, 30);
        if(nptr != &str[0] + str.size())
            std::cout << str << " in base 30 is invalid."
                      << " The first invalid digit is " << *nptr << '\n';
    }

Output:

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

### [edit] See also

wcstoimaxwcstoumax (C++11)(C++11) | converts a wide string to std::intmax_t or std::uintmax_t (function) [edit]
strtolstrtoll | converts a byte string to an integer value (function) [edit]
strtoul strtoull | converts a byte string to an unsigned integer value (function) [edit]
C documentation for strtoimax, strtoumax

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