C++ Templates MCQ: C++ Templates Multiple Choice Questions

Can we have overloading of the function templates?

Output of the below code?

#include <iostream>
using namespace std;

template <int i>
void fun()
{
    i = 20;
    cout << i;
}

int main()
{
    fun<10>();

    return 0;
}

Which of the following describes a potentially surprising result of using templates?

The output of the below code?

#include <iostream>
using namespace std;

template<int n> struct funStruct
{
    static const int val = 2*funStruct<n-1>::val;
};

template<> struct funStruct<0>
{
    static const int val = 1 ;
};

int main()
{
    cout << funStruct<10>::val << endl;

    return 0;
}

What will be the output of the below code?

#include <iostream>

using namespace std;

template <typename T>
void fun(const T&x)
{
    static int count = 0;
    cout << "x = " << x << " count = " << count << endl;
    ++count;
    return;
}

int main()
{
    fun<int> (1);
    cout << endl;

    fun<int>(1);
    cout << endl;

    fun<double>(1.1);
    cout << endl;

    return 0;
}

Which of the following is true about templates?

1.  A template is a feature of C++ that allows us to write one code for different data types.

2. We can write one function that can be used for all data types including user-defined types. Like sort(), max(), min(), ..etc.

3. We can write one class or struct that can be used for all data types including user-defined types. Like Linked List, Stack, Queue ..etc.

4. Template is an example of compile-time polymorphism.

What is the result of trying to run this program?

#include <iostream>
template <int T>
struct X
{
    enum val {v = T * X<T-1>::v };
};

template <>
struct X<0>
{
    enum val {v = 1 };
};

int main()
{
    std::cout<<X<5>::v;
}

From where does the template class derived?

When are templates usually instantiated?

Which of the following is an invalid template declaration:

What is the output of the below code?

#include <iostream>
using namespace std;

template <typename T>
T max(T x, T y)
{
    return (x > y)? x : y;
}

int main()
{
    cout << max(3, 7) << std::endl;
    cout << max(3.0, 7.0) << std::endl;
    cout << max(3, 7.0) << std::endl;

    return 0;
}

What is the validity of template parameters?

Which keyword can be used in template?

What problems can a templated member function cause?

Output of following program? Assume that the size of int is 4 bytes and size of double is 8 bytes, and there is no alignment done by the compiler.

#include<iostream>

using namespace std;

template<class T, class U, class V=double>
class A
{
    T x;
    U y;
    V z;
    static int count;
};

int main()
{
    A<int, int> a;
    A<double, double> b;

    cout << sizeof(a) << endl;
    cout << sizeof(b) << endl;

    return 0;
}

Which of the following is incorrect in C++ ?

1. When we write overloaded function we must code the function for each usage.
2. When we write function template we code the function only once.
3. It is difficult to debug macros.
4. Templates are more efficient than macros

When must template functions have explicit template parameters?

Is there any semantic difference between class and typename in a type-parameter-key?

Can I separate the definition of my template class from its declaration and put it inside a .cpp file?

Output of the program?

#include <iostream>
using namespace std;

template <class T, int max>
int arrMin(T arr[], int n)
{
    int m = max;
    int i;
    for (i = 0; i < n; i++)
    {
        if (arr[i] < m)
        {
            m = arr[i];
        }
    }
    return m;
}

int main()
{
    int arr1[]  = {10, 20, 15, 12};
    int n1 = sizeof(arr1)/sizeof(arr1[0]);

    char arr2[] = {1, 2, 3};
    int n2 = sizeof(arr2)/sizeof(arr2[0]);

    cout << arrMin<int, 10000>(arr1, n1) << endl;
    cout << arrMin<char, 256>(arr2, n2);

    return 0;
}

Which of the things does not require instantiation?

What is the output?

#include <iostream>
using namespace std;

template <typename T, int count>
void Test(T x)
{
    T val[count];
    for(int i = 0; i < count; i++)
    {
        val[i] = x++;
        cout <<  val[i] << endl;
    }
};

int main()
{
    float data = 2.1;
    Test<float, 3>(data);
    
    return 0;
}

The output of the following program? Assume that the size of char is 1 byte and size of int is 4 bytes, and there is no alignment done by the compiler.

#include<iostream>

using namespace std;

template<class T, class U>
class A
{
    T x;
    U y;
    static int count;
};

int main()
{
    A<char, char> a;
    A<int, int> b;
    cout << sizeof(a) << endl;
    cout << sizeof(b) << endl;

    return 0;
}

Given the below code, what happens when a method invokes callFunc on an object of type obj?

#include <iostream>

template <class X>
func(X val) 
{

}

template <> 
func<double>(double val) 
{

}

class obj
{
public:
    callFunc()
    {
        func(4.5);
    }
private:
    func(int val) {}
};

Are templates conceptually related to polymorphism?

Select the correct statement.

#include <iostream>

template<class T> class X
{
    static T t;
};


class Y
{
private:
    struct S
    {
    };
    X<S> x;
};


int main()
{

    return 0;
}

Which of the following provides the best description of an entity type?

Output of the below code?

#include <iostream>
using namespace std;

template <class T>
T max (T &a, T &b)
{
    return (a > b)? a : b;
}

template <>
int max <int> (int &a, int &b)
{
    cout << "Called ";

    return (a > b)? a : b;
}

int main ()
{
    int a = 10, b = 20;

    cout << max <int> (a, b);

    return 0;
}

In general, is it possible to completely hide the source code of a library written using templates?

What is the output of the below code?

#include <iostream>
using namespace std;

template <class T>
class Test
{
private:
    T val;
public:
    static int count;
    Test()
    {
        count++;
    }
};

template<class T>
int Test<T>::count = 0;

int main()
{
    Test<int> a;
    Test<int> b;
    Test<double> c;

    cout << Test<int>::count   << endl;
    cout << Test<double>::count << endl;

    return 0;
}