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std::is_compound Template in C++

  • Last Updated : 19 Nov, 2018

The std::is_compound template of C++ STL is used to check the whether the type is a compound type or not. It returns a boolean value showing the same.

Syntax:

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template < class T > struct is_compound;

Parameter: This template contains single parameter T (Trait class) to check whether T is a compound type or not.

Return Value: This template returns a boolean value as shown below:



  • True: if the type is a compound type.
  • False: if the type is a non-compound type.

Below programs illustrate the is_compound template in C++ STL:

Program 1:




// C++ program to illustrate
// is_compound template
  
#include <iostream>
#include <type_traits>
using namespace std;
  
// main program
struct GFG1 {
};
  
union GFG2 {
    int var1;
    float var2;
};
  
int main()
{
    cout << boolalpha;
    cout << "is_compound:"
         << endl;
    cout << "GFG1: "
         << is_compound<GFG1>::value
         << endl;
    cout << "GFG2: "
         << is_compound<GFG2>::value
         << endl;
    cout << "int: "
         << is_compound<int>::value
         << endl;
    cout << "int*: "
         << is_compound<int*>::value
         << endl;
    return 0;
}
Output:
is_compound:
GFG1: true
GFG2: true
int: false
int*: true

Program 2:




// C++ program to illustrate
// is_compound template
  
#include <iostream>
#include <type_traits>
using namespace std;
  
class GFG1 {
};
  
enum class GFG2 { var1,
               var2,
               var3,
               var4
};
  
// main program
int main()
{
    cout << boolalpha;
    cout << "is_compound:"
         << endl;
    cout << "GFG1: "
         << is_compound<GFG1>::value
         << endl;
    cout << "GFG2: "
         << is_compound<GFG2>::value
         << endl;
    cout << "int[10]: "
         << is_compound<int[10]>::value
         << endl;
    cout << "int &: "
         << is_compound<int&>::value
         << endl;
    cout << "char: "
         << is_compound<char>::value
         << endl;
  
    return 0;
}
Output:
is_compound:
GFG1: true
GFG2: true
int[10]: true
int &: true
char: false

Program 3:




// C++ program to illustrate
// is_compound template
  
#include <iostream>
#include <type_traits>
using namespace std;
  
// driver code
int main()
{
    class gfg {
    };
  
    cout << boolalpha;
    cout << "is_compound:"
         << endl;
    cout << "int(gfg::*): "
         << is_compound<int(gfg::*)>::value
         << endl;
    cout << "float: "
         << is_compound<float>::value
         << endl;
    cout << "double: "
         << is_compound<double>::value
         << endl;
    cout << "int(int): "
         << is_compound<int(int)>::value
         << endl;
  
    return 0;
}
Output:
is_compound:
int(gfg::*): true
float: false
double: false
int(int): true



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