std::stod, std::stof, std::stold in C++
- std::stod() : It convert string into double.
Syntax:double stod( const std::string& str, std::size_t* pos = 0 ); double stod( const std::wstring& str, std::size_t* pos = 0 ); Return Value: return a value of type double Parameters str : the string to convert pos : address of an integer to store the number of characters processed. This parameter can also be a null pointer, in which case it is not used.
// CPP program to illustrate
// std::stod()
#include <string>
#include <iostream>
int
main(
void
)
{
std::string str =
"y=4.4786754x+5.6"
;
double
y, x, a, b;
y = 0;
x = 0;
// offset will be set to the length of
// characters of the "value" - 1.
std::
size_t
offset = 0;
a = std::stod(&str[2], &offset);
b = std::stod(&str[offset + 3]);
std::cout << b;
return
0;
}
Output:
5.6
Another Example :
// CPP program to illustrate
// std::stod()
#include <iostream>
#include <string>
using
namespace
std;
int
main()
{
string b =
"5"
;
double
a = stod(b);
int
c = stoi(b);
cout << b <<
" "
<< a <<
" "
<< c << endl;
}
Output:
5 5 5
If conversion is not performed, an invalid_argument exception is thrown. If the value read is out of the range of representable values by a double an out_of_range exception is thrown. An invalid idx causes undefined behavior.
- std::stof : It convert string into float.
Syntax:float stof( const string& str, size_t* pos = 0 ); float stof( const wstring& str, size_t* pos = 0 ); Parameters str : the string to convert pos : address of an integer to store the number of characters processed This parameter can also be a null pointer, in which case it is not used. Return value: it returns value of type float.
Example 1:
// CPP program to illustrate
// std::stof()
#include <iostream>
#include <string>
int
main()
{
std::string x;
x =
"20"
;
float
y = std::stof(x) + 2.5;
std::cout << y;
return
0;
}
Output:
22.5
Example 2:
// CPP program to illustrate
// std::stof()
#include <iostream>
#include <string>
int
main()
{
std::string str =
"5000.5"
;
float
x = std::stof(str);
std::cout << x;
return
0;
}
Output:
5000.5
If no conversion could be performed, an invalid_argument exception is thrown.
- std::stold : It convert string into long double.
Syntax:long double stold( const string& str, size_t *pos = 0 ); long double stold (const wstring& str, size_t* pos = 0); Parameters : str : the string to convert pos : address of integer to store the index of the first unconverted character. This parameter can also be a null pointer, in which case it is not used. Return value : it returns value of type long double.
Examples 1:
// CPP program to illustrate
// std::stold()
#include <iostream>
#include <string>
int
main()
{
std::string str =
"500087"
;
long
double
x = std::stold(str);
std::cout << x;
return
0;
}
Output:
500087
Example 2:
// CPP program to illustrate
// std::stold()
#include <iostream>
#include <string>
int
main()
{
std::string x;
x =
"2075"
;
long
double
y = std::stof(x) + 2.5;
std::cout << y;
return
0;
}
Output:
2077.5