[string.conversions]

# 27 Strings library [[strings]](./#strings)

## 27.4 String classes [[string.classes]](string.classes#string.conversions)

### 27.4.5 Numeric conversions [string.conversions]

[🔗](#lib:stoi)

`int stoi(const string& str, size_t* idx = nullptr, int base = 10);
long stol(const string& str, size_t* idx = nullptr, int base = 10);
unsigned long stoul(const string& str, size_t* idx = nullptr, int base = 10);
long long stoll(const string& str, size_t* idx = nullptr, int base = 10);
unsigned long long stoull(const string& str, size_t* idx = nullptr, int base = 10);
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5214)

*Effects*: The first two functions call strtol(str.c_str(), ptr, base),
and the last three functions call strtoul(str.c_str(), ptr, base),strtoll(str.c_str(), ptr, base), and strtoull(​str.c_str(), ptr,
base), respectively[.](#1.sentence-1)

Each function returns the converted result, if any[.](#1.sentence-2)

The
argument ptr designates a pointer to an object internal to the function
that is used to determine what to store at *idx[.](#1.sentence-3)

If the function does
not throw an exception and idx != nullptr, the function stores in *idx the index of the first unconverted element of str[.](#1.sentence-4)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5225)

*Returns*: The converted result[.](#2.sentence-1)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5229)

*Throws*: invalid_argument if strtol, strtoul,strtoll, or strtoull reports that no conversion can be
performed[.](#3.sentence-1)

Throws out_of_range if strtol, strtoul,strtoll or strtoull sets errno to ERANGE,
or if the converted value is outside the range of representable values
for the return type[.](#3.sentence-2)

[🔗](#lib:stof)

`float stof(const string& str, size_t* idx = nullptr);
double stod(const string& str, size_t* idx = nullptr);
long double stold(const string& str, size_t* idx = nullptr);
`

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5249)

*Effects*: These functions callstrtof(str.c_str(), ptr), strtod(str.c_str(), ptr), andstrtold(​str.c_str(), ptr), respectively[.](#4.sentence-1)

Each function returns
the converted result, if any[.](#4.sentence-2)

The argument ptr designates a pointer to
an object internal to the function that is used to determine what to store at*idx[.](#4.sentence-3)

If the function does not throw an exception and idx != nullptr,
the function stores in *idx the index of the first unconverted element
of str[.](#4.sentence-4)

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5260)

*Returns*: The converted result[.](#5.sentence-1)

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5264)

*Throws*: invalid_argument if strtof, strtod, orstrtold reports that no conversion can be performed[.](#6.sentence-1)

Throwsout_of_range if strtof, strtod, orstrtold sets errno to ERANGE or if the converted value is outside the range of representable
values for the return type[.](#6.sentence-2)

[🔗](#lib:to_string)

`string to_string(int val);
string to_string(unsigned val);
string to_string(long val);
string to_string(unsigned long val);
string to_string(long long val);
string to_string(unsigned long long val);
string to_string(float val);
string to_string(double val);
string to_string(long double val);
`

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5288)

*Returns*: format("{}", val)[.](#7.sentence-1)

[🔗](#lib:stoi_)

`int stoi(const wstring& str, size_t* idx = nullptr, int base = 10);
long stol(const wstring& str, size_t* idx = nullptr, int base = 10);
unsigned long stoul(const wstring& str, size_t* idx = nullptr, int base = 10);
long long stoll(const wstring& str, size_t* idx = nullptr, int base = 10);
unsigned long long stoull(const wstring& str, size_t* idx = nullptr, int base = 10);
`

[8](#8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5307)

*Effects*: The first two functions call wcstol(str.c_str(), ptr, base),
and the last three functions call wcstoul(str.c_str(), ptr, base),wcstoll(str.c_str(), ptr, base), and wcstoull(​str.c_str(), ptr,
base), respectively[.](#8.sentence-1)

Each function returns the converted result, if any[.](#8.sentence-2)

The
argument ptr designates a pointer to an object internal to the function
that is used to determine what to store at *idx[.](#8.sentence-3)

If the function does
not throw an exception and idx != nullptr, the function stores in *idx the index of the first unconverted element of str[.](#8.sentence-4)

[9](#9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5318)

*Returns*: The converted result[.](#9.sentence-1)

[10](#10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5322)

*Throws*: invalid_argument if wcstol, wcstoul, wcstoll, orwcstoull reports that no conversion can be performed[.](#10.sentence-1)

Throwsout_of_range if the converted value is outside the range of representable values
for the return type[.](#10.sentence-2)

[🔗](#lib:stof_)

`float stof(const wstring& str, size_t* idx = nullptr);
double stod(const wstring& str, size_t* idx = nullptr);
long double stold(const wstring& str, size_t* idx = nullptr);
`

[11](#11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5340)

*Effects*: These functions call wcstof(str.c_str(), ptr),wcstod(str.c_str(), ptr), and wcstold(​str.c_str(), ptr),
respectively[.](#11.sentence-1)

Each function returns the converted
result, if any[.](#11.sentence-2)

The argument ptr designates a pointer to an object internal to
the function that is used to determine what to store at *idx[.](#11.sentence-3)

If the function
does not throw an exception and idx != nullptr, the function stores in *idx the index of the first unconverted element of str[.](#11.sentence-4)

[12](#12)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5350)

*Returns*: The converted result[.](#12.sentence-1)

[13](#13)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5354)

*Throws*: invalid_argument if wcstof, wcstod, or wcstold reports that no
conversion can be performed[.](#13.sentence-1)

Throws out_of_range if wcstof, wcstod, orwcstold sets errno to ERANGE[.](#13.sentence-2)

[🔗](#lib:to_wstring)

`wstring to_wstring(int val);
wstring to_wstring(unsigned val);
wstring to_wstring(long val);
wstring to_wstring(unsigned long val);
wstring to_wstring(long long val);
wstring to_wstring(unsigned long long val);
wstring to_wstring(float val);
wstring to_wstring(double val);
wstring to_wstring(long double val);
`

[14](#14)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/strings.tex#L5375)

*Returns*: format(L"{}", val)[.](#14.sentence-1)