is_void template in C++
Last Updated :
19 Nov, 2018
The std::is_void template of C++ STL is used to check whether the type is a void or not. It returns a boolean value showing the same.
Syntax:
template < class T > struct is_void;
Parameter: This template contains single parameter T (Trait class) to check whether T is a void type or not.
Return Value: This template returns a boolean value as shown below:
- True: if the type is a void.
- False: if the type is a non-void.
Below programs illustrate the std::is_void template in C++ STL:
Program 1:
#include <iostream>
#include <type_traits>
using namespace std;
int main()
{
cout << boolalpha;
cout << "is_void:"
<< '\n' ;
cout << "void:"
<< is_void< void >::value
<< '\n' ;
cout << "const void:"
<< is_void< const void >::value
<< '\n' ;
cout << "int:"
<< is_void< int >::value
<< '\n' ;
cout << "char:"
<< is_void< char >::value
<< '\n' ;
return 0;
}
|
Output:
is_void:
void:true
const void:true
int:false
char:false
Program 2:
#include <iostream>
#include <type_traits>
using namespace std;
int main()
{
cout << boolalpha;
cout << "is_void:"
<< '\n' ;
cout << "double:"
<< is_void< double >::value
<< '\n' ;
cout << "float:"
<< is_void< float >::value
<< '\n' ;
cout << "volatile void:"
<< is_void< volatile void >::value
<< '\n' ;
cout << "const volatile void:"
<< is_void< const volatile void >::value
<< '\n' ;
return 0;
}
|
Output:
is_void:
double:false
float:false
volatile void:true
const volatile void:true
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