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

< cpp‎ | string‎ | basic string
Defined in header <string>
int       stoi( const std::string& str, size_t *pos = 0, int base = 10 );
(1) (since C++11)
long      stol( const std::string& str, size_t *pos = 0, int base = 10 );
(2) (since C++11)
long long stoll( const std::string& str, 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)
2) calls std::strtol(str.c_str(), &ptr, base)
3) calls std::strtoll(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. In non-default locales, additional numeric formats may be accepted.

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

#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';


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

[edit] See also

converts a byte string to an integer value
(function) [edit]
converts a string to an unsigned integer
(function) [edit]
converts a string to a floating point value
(function) [edit]
converts an integral or floating point value to string
(function) [edit]