Defined in header
intstoi(conststd::string&str,std::size_t*pos=nullptr,intbase=10); (1) (since C++11)intstoi(conststd::wstring&str,std::size_t*pos=nullptr,intbase=10); (2) (since C++11)longstol(conststd::string&str,std::size_t*pos=nullptr,intbase=10); (3) (since C++11)longstol(conststd::wstring&str,std::size_t*pos=nullptr,intbase=10); (4) (since C++11)longlongstoll(conststd::string&str,std::size_t*pos=nullptr,intbase=10); (5) (since C++11)longlongstoll(conststd::wstring&str,std::size_t*pos=nullptr,intbase=10); (6) (since C++11)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
) 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
.
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
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
if no conversion could be performed.
if the converted value would fall out of the range of the result type or if the underlying function (
or
) sets
to
.
Example
Run this code
#include<iomanip>#include<iostream>#include<stdexcept>#include<string>#include<utility>intmain(){constautodata={"45","+45"," -45","3.14159","31337 with words","words and 2","12345678901",};for(conststd::strings:data){std::size_tpos{};try{std::cout<<"std::stoi("<<std::quoted(s)<<"): ";constinti{std::stoi(s,&pos)};std::cout<<i<<"; pos: "<<pos<<'\n';}catch(std::invalid_argumentconst&ex){std::cout<<"std::invalid_argument::what(): "<<ex.what()<<'\n';}catch(std::out_of_rangeconst&ex){std::cout<<"std::out_of_range::what(): "<<ex.what()<<'\n';constlonglongll{std::stoll(s,&pos)};std::cout<<"std::stoll("<<std::quoted(s)<<"): "<<ll<<"; pos: "<<pos<<'\n';}}std::cout<<"\nCalling with different radixes:\n";for(constauto&[s,base]:{std::pair<constchar*,int>{"11",2},{"22",3},{"33",4},{"77",8},{"99",10},{"FF",16},{"jJ",20},{"Zz",36}}){constinti{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
C++11
would not be thrown if
or
sets
to
will throw See also
(C++11)(C++11)
converts a string to an unsigned integer
(function)
(C++11)(C++11)(C++11)
converts a string to a floating point value
(function)
(C++11)
converts a byte string to an integer value
(function)
(C++11)
converts a byte string to an unsigned integer value
(function)
(C++11)(C++11)
converts a byte string to
or
(function)
(C++17)
converts a character sequence to an integer or floating-point value
(function)
(C++11)
converts a byte string to an integer value
(function)
(C++11)
converts an integral or floating-point value to string
(function)
(C++11)
converts an integral or floating-point value to wstring
(function)