valarray apply() in C++

The apply() function is defined in valarray header file. This function returns a valarray with each of its elements initialized to the result of applying func to its corresponding element in *this.

Syntax:

valarray apply (T func(T)) const;
valarray apply (T func(const T&)) const;

Parameter: This method accepts a mandatory parameter func which represents the pointer to the function taking an argument of type T.

Return Value: This method returns a valarray object with the results of applying func to all the elements of *this.

Below programs illustrate the above function:

Example 1:-

// C++ program to demonstrate
// example of apply() function.

#include <bits/stdc++.h>
using namespace std;

int main()
{

    // Initializing valarray
    valarray<int> varr = { 15, 10, 30, 33, 40 };

    // Declaring new valarray
    valarray<int> varr1;

    // Using apply() to increment all elements by 5
    varr1 = varr.apply([](int x) { return x = x + 5; });

    // Displaying new elements value
    cout << "The new valarray "
         << "with manipulated values is : ";

    for (int& x : varr1)
        cout << x << " ";

    cout << endl;

    return 0;
}

Output:

The new valarray with manipulated values is : 20 15 35 38 45

Example 2:-

// C++ program to demonstrate
// example of apply() function.

#include <bits/stdc++.h>
using namespace std;

int main()
{

    // Initializing valarray
    valarray<int> varr = { 15, 10, 30, 33, 40 };

    // Declaring new valarray
    valarray<int> varr1;

    // Using apply() to decrement all elements by 5
    varr1 = varr.apply([](int x) { return x = x - 5; });

    // Displaying new elements value
    cout << "The new valarray"
         << " with manipulated values is : ";

    for (int& x : varr1)
        cout << x << " ";

    cout << endl;

    return 0;
}

Output:

The new valarray with manipulated values is : 10 5 25 28 35