is_trivial function in C++

In this article we will be discussing the working, syntax and examples of std::is_trivial template in C++ STL.

is_trivial is a template which comes under <type_traits> header file. This template is used to check whether the given type T is a trivial class or not

What is a trivial class type in C++?

We say a type as a Trivial type, when its data is stored in a contiguous manner and which accepts only static default initialization. It can include arrays of any type, classes and scalar type.

Trivial class is a class which is trivially default constructed and trivially copyable. There are some points which should be taken care while making a class as trivial −

• It must have no virtual members or virtual base class.
• No non static members.
• No Base class with non-static members

Syntax

template <class T> is_trivial;

Parameters

The template can have only parameters of type T, and check whether the given type is a trivial type class or not.

Return value

It returns a Boolean value, true if the given type is a trivial class type, and false if the given type is not a trivial class type.

Example

Input: class A {};
   class B { B() {} };
   class D { virtual void fn() {} };
   cout<<”A: ”<<is_trivial<A>;
   cout<<”B: ”<<is_trivial<B>;
   cout<<”D: ”<<is_trivial<D>;
Output:
A: True
B: False
D: False

Example

 Live Demo

#include <iostream>
#include <type_traits>
using namespace std;
class TP_1 {
};
class TP_2 {
   TP_2(){
   }
};
class TP_3 : TP_2 {
};
class TP_4 {
   virtual void dummy() {
   }
};
int main() {
   std::cout << std::boolalpha; //Returns value in boolean type
   std::cout << "TP_1: " << std::is_trivial<TP_1>::value << endl;
   std::cout << "TP_2: " << std::is_trivial<TP_2>::value << endl;
   std::cout << "TP_3: " << std::is_trivial<TP_3>::value << endl;
   std::cout << "TP_4: " << std::is_trivial<TP_4>::value << endl;
   return 0;
}

Output

If we run the above code it will generate the following output −

TP_1: true
TP_2: false
TP_3: false
TP_4: false