NAME¶

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

Synopsis¶

Defined in header <string>
int stoi ( const std::string& str, (1) (since C++11)
std::size_t* pos = nullptr, int base = 10 );
int stoi ( const std::wstring& str, (2) (since C++11)
std::size_t* pos = nullptr, int base = 10 );
long stol ( const std::string& str, (3) (since C++11)
std::size_t* pos = nullptr, int base = 10 );
long stol ( const std::wstring& str, (4) (since C++11)
std::size_t* pos = nullptr, int base = 10 );
long long stoll( const std::string& str, (5) (since C++11)
std::size_t* pos = nullptr, int base = 10 );
long long stoll( const std::wstring& str, (6) (since C++11)
std::size_t* pos = nullptr, int base = 10 );

Interprets a signed integer value in the string str.

Let ptr be an internal (to the conversion functions) pointer of type char* (1,3,5)
or wchar_t* (2,4,6), accordingly.

1) Calls std::strtol(str.c_str(), &ptr, base).
2) Calls std::wcstol(str.c_str(), &ptr, base).
3) Calls std::strtol(str.c_str(), &ptr, base).
4) Calls std::wcstol(str.c_str(), &ptr, base).
5) Calls std::strtoll(str.c_str(), &ptr, base).
6) Calls std::wcstoll(str.c_str(), &ptr, base).

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) 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 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.

If pos is not a null pointer, then ptr will receive an address of the first
unconverted character in str.c_str(), and the index of that character will be
calculated and stored in *pos, giving the number of characters that were processed
by the conversion.

Parameters¶

str - the string to convert
pos - address of an integer to store the number of characters processed
base - the number base

Return value¶

Integer value corresponding to the content of str.

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.

Example¶

// Run this code

#include <iomanip>
#include <iostream>
#include <stdexcept>
#include <string>
#include <utility>

int main()
{
const auto data =
{
"45",
"+45",
" -45",
"3.14159",
"31337 with words",
"words and 2",
"12345678901",
};

for (const std::string s : data)
{
std::size_t pos{};
try
{
std::cout << "std::stoi(" << std::quoted(s) << "): ";
const int i{std::stoi(s, &pos)};
std::cout << i << "; pos: " << pos << '\n';
}
catch (std::invalid_argument const& ex)
{
std::cout << "std::invalid_argument::what(): " << ex.what() << '\n';
}
catch (std::out_of_range const& ex)
{
std::cout << "std::out_of_range::what(): " << ex.what() << '\n';
const long long ll{std::stoll(s, &pos)};
std::cout << "std::stoll(" << std::quoted(s) << "): " << ll
<< "; pos: " << pos << '\n';
}
}

std::cout << "\nCalling with different radixes:\n";
for (const auto& [s, base] : {std::pair<const char*, int>
{"11", 2}, {"22", 3}, {"33", 4}, {"77", 8},
{"99", 10}, {"FF", 16}, {"jJ", 20}, {"Zz", 36}})
{
const int i{std::stoi(s, nullptr, base)};
std::cout << "std::stoi(" << std::quoted(s)
<< ", nullptr, " << base << "): " << i << '\n';
}
}

Possible output:¶

std::stoi("45"): 45; pos: 2
std::stoi("+45"): 45; pos: 3
std::stoi(" -45"): -45; pos: 4
std::stoi("3.14159"): 3; pos: 1
std::stoi("31337 with words"): 31337; pos: 5
std::stoi("words and 2"): std::invalid_argument::what(): stoi
std::stoi("12345678901"): std::out_of_range::what(): stoi
std::stoll("12345678901"): 12345678901; pos: 11

Calling with different radixes:
std::stoi("11", nullptr, 2): 3
std::stoi("22", nullptr, 3): 8
std::stoi("33", nullptr, 4): 15
std::stoi("77", nullptr, 8): 63
std::stoi("99", nullptr, 10): 99
std::stoi("FF", nullptr, 16): 255
std::stoi("jJ", nullptr, 20): 399
std::stoi("Zz", nullptr, 36): 1295

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
std::out_of_range would not be thrown if
LWG 2009 C++11 std::strtol or std::strtoll sets errno to will throw
ERANGE

See also¶

stoul
stoull converts a string to an unsigned integer
(C++11) (function)
(C++11)
stof
stod
stold converts a string to a floating point value
(C++11) (function)
(C++11)
(C++11)
strtol converts a byte string to an integer value
strtoll (function)
(C++11)
strtoul converts a byte string to an unsigned integer value
strtoull (function)
(C++11)
strtoimax
strtoumax converts a byte string to std::intmax_t or std::uintmax_t
(C++11) (function)
(C++11)
from_chars converts a character sequence to an integer or floating-point value
(C++17) (function)
atoi
atol converts a byte string to an integer value
atoll (function)
(C++11)
to_string converts an integral or floating-point value to string
(C++11) (function)
to_wstring converts an integral or floating-point value to wstring
(C++11) (function)