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# std::stoi, std::stol, std::stoll

From cppreference.com
< cpp‎ | string‎ | basic string

Defined in header `<string>` |  |
int stoi( const std::string& str, std::size_t* pos = 0, int base = 10 ); int stoi( const std::wstring& str, std::size_t* pos = 0, int base = 10 ); | (1) | (since C++11)
long stol( const std::string& str, std::size_t* pos = 0, int base = 10 ); long stol( const std::wstring& str, std::size_t* pos = 0, int base = 10 ); | (2) | (since C++11)
long long stoll( const std::string& str, std::size_t* pos = 0, int base = 10 ); long long stoll( const std::wstring& str, std::size_t* pos = 0, int base = 10 ); | (3) | (since C++11)

Interprets a signed integer value in the string `str`.

1) calls std::strtol(str.c_str(), &ptr, base) or std::wcstol(str.c_str(), &ptr, base)
2) calls std::strtol(str.c_str(), &ptr, base) or std::wcstol(str.c_str(), &ptr, base)
3) calls std::strtoll(str.c_str(), &ptr, base) or std::wcstoll(str.c_str(), &ptr, base)

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.

If `pos` is passed a value other than 0 or nullptr, then a pointer `ptr` - internal to the conversion functions - will receive the address of the first unconverted character, and the index of that character will be calculated and stored in `*pos`.

### [edit] Parameters

str | - | the string to convert
pos | - | address of an integer to store the index of the first unconverted character
base | - | the number base

### [edit] Return value

The string converted to the specified signed integer type.

### [edit] Exceptions

- std::invalid_argument if no conversion could be performed
- std::out_of_range if the converted value would fall out of the range of the result type or if the underlying function (std::strtol or std::strtoll) sets errno to ERANGE.

### [edit] Example

Run this code

    #include <iostream>
    #include <string>

    int main()
    {
        std::string str1 = "45";
        std::string str2 = "3.14159";
        std::string str3 = "31337 with words";
        std::string str4 = "words and 2";

        int myint1 = std::stoi(str1);
        int myint2 = std::stoi(str2);
        int myint3 = std::stoi(str3);
        // error: 'std::invalid_argument'
        // int myint4 = std::stoi(str4);

        std::cout << "std::stoi(\"" << str1 << "\") is " << myint1 << '\n';
        std::cout << "std::stoi(\"" << str2 << "\") is " << myint2 << '\n';
        std::cout << "std::stoi(\"" << str3 << "\") is " << myint3 << '\n';
        //std::cout << "std::stoi(\"" << str4 << "\") is " << myint4 << '\n';
    }

Output:

    std::stoi("45") is 45
    std::stoi("3.14159") is 3
    std::stoi("31337 with words") is 31337

### [edit] See also

atoi atol atoll | converts a byte string to an integer value (function) [edit]
stoul stoull (C++11)(C++11) | converts a string to an unsigned integer (function) [edit]
stof stod stold (C++11)(C++11)(C++11) | converts a string to a floating point value (function) [edit]
to_string (C++11) | converts an integral or floating point value to `string` (function) [edit]

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