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# std::valarray::apply

From cppreference.com
< cpp‎ | numeric‎ | valarray

valarray<T> apply( T func(T) ) const; |  |
valarray<T> apply( T func(const T&) ) const; |  |

Returns a new valarray of the same size with values which are acquired by applying function `func` to the previous values of the elements.

### [edit] Parameters

func | - | function to apply to the values

### [edit] Return value

The resulting valarray with values acquired by applying function `func`.

### [edit] Notes

The function can be implemented with the return type different from std::valarray. In this case, the replacement type has the following properties:

  - All const member functions of std::valarray are provided.
  - std::valarray, std::slice_array, std::gslice_array, std::mask_array and std::indirect_array can be constructed from the replacement type.
  - All functions accepting an argument of type const std::valarray& except `begin()` and `end()` (since C++14) should also accept the replacement type.
  - All functions accepting two arguments of type const std::valarray& should accept every combination of const std::valarray& and the replacement type.
  - The return type does not add more than two levels of template nesting over the most deeply-nested argument type.

### [edit] Example

calculates and prints the first 10 factorials

Run this code

    #include <iostream>
    #include <valarray>
    #include <cmath>

    int main()
    {
        std::valarray<int> v = {1,2,3,4,5,6,7,8,9,10};
        v = v.apply([](int n)->int {
                        return std::round(std::tgamma(n+1));
                    });
        for(auto n : v) {
            std::cout << n << ' ';
        }
        std::cout << '\n';
    }

Output:

    1 2 6 24 120 720 5040 40320 362880 3628800

### [edit] See also

for_each | applies a function to a range of elements (function template) [edit]

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