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has_trivial_constructor Class

Tests if type has trivial default constructor.

template<class Ty>
    struct has_trivial_constructor;

Ty

The type to query.

An instance of the type predicate holds true if the type Ty is a class that has a trivial constructor, otherwise it holds false.

A constructor for a class Ty is trivial if:

it is an implicitly declared default constructor

the class Ty has no virtual functions

the class Ty has no virtual bases

all the direct bases of the class Ty have trivial constructors

the classes of all the non-static data members of class type have trivial constructors

the classes of all the non-static data members of type array of class have trivial constructors

 

// std_tr1__type_traits__has_trivial_constructor.cpp 
// compile with: /EHsc 
#include <type_traits> 
#include <iostream> 
 
struct trivial 
    { 
    int val; 
    }; 
 
struct throws 
    { 
    throws() throw(int) 
        { 
        } 
 
    throws(const throws&) throw(int) 
        { 
        } 
 
    throws& operator=(const throws&) throw(int) 
        { 
        } 
 
    int val; 
    }; 
 
int main() 
    { 
    std::cout << "has_trivial_constructor<trivial> == " << std::boolalpha 
        << std::has_trivial_constructor<trivial>::value << std::endl; 
    std::cout << "has_trivial_constructor<throws> == " << std::boolalpha 
        << std::has_trivial_constructor<throws>::value << std::endl; 
 
    return (0); 
    } 
 
has_trivial_constructor<trivial> == true
has_trivial_constructor<throws> == false

Header: <type_traits>

Namespace: std

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