std is_union() template in C++
The std::is_union template of C++ STL is used to check whether the given type is union or not. It returns a boolean value showing the same.
Syntax:
template <class T> struct is_union;
Parameter: This template accepts single parameter T (Trait class) to check whether T is a union or not.
Return Value: This template returns a boolean value as shown below:
- True: If a type is a union class.
- False: If a type is a non-union class.
Below programs illustrate the std::is_union template in C++:
Program 1::
#include <iostream>
#include <type_traits>
using namespace std;
struct GFG1 {
};
union GFG2 {
int var1;
float var2;
};
int main()
{
cout << boolalpha;
cout << "is_union:" << endl;
cout << "GFG1: "
<< is_union<GFG1>::value << endl;
cout << "GFG2: "
<< is_union<GFG2>::value << endl;
return 0;
}
|
Output:
is_union:
GFG1: false
GFG2: true
Program 2:
#include <iostream>
#include <type_traits>
using namespace std;
union GFG1 {
int var1;
float var2;
char var3;
};
struct GFG2 {
union {
int var4;
float var5;
};
};
int main()
{
cout << boolalpha;
cout << "is_union:" << endl;
cout << "int: "
<< is_union< int >::value << endl;
cout << "GFG1: "
<< is_union<GFG1>::value << endl;
cout << "GFG2: "
<< is_union<GFG2>::value << endl;
return 0;
}
|
Output:
is_union:
int: false
GFG1: true
GFG2: false
Last Updated :
19 Nov, 2018
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