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valarray apply() in C++

Last Updated : 11 Jul, 2025
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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:- CPP
// 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:- CPP
// 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

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