table of contents
std::valarray::apply(3) | C++ Standard Libary | std::valarray::apply(3) |
NAME¶
std::valarray::apply - std::valarray::apply
Synopsis¶
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.
Parameters¶
func - function to apply to the values
Return value¶
The resulting valarray with values acquired by applying function func.
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.
* For every function taking a const std::valarray<T>&
except begin() and end()
(since C++11), identical functions taking the replacement types shall
be added;
* For every function taking two const std::valarray<T>& arguments,
identical
functions taking every combination of const std::valarray<T>& and
replacement
types shall be added.
* The return type does not add more than two levels of template nesting over
the
most deeply-nested argument type.
Possible implementation¶
Following straightforward implementations can be replaced by
expression templates
for a higher efficiency.
template<class T>
valarray<T> valarray<T>::apply(T func(T)) const
{
valarray<T> other = *this;
for (T& i : other)
i = func(i);
return other;
}
template<class T>
valarray<T> valarray<T>::apply(T func(const T&)) const
{
valarray<T> other = *this;
for (T& i : other)
i = func(i);
return other;
}
Example¶
Calculates and prints the first 10 factorials.
// Run this code
#include <cmath>
#include <iostream>
#include <valarray>
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
See also¶
for_each applies a function to a range of elements
(function template)
ranges::for_each applies a function to a range of elements
(C++20) (niebloid)
Hidden category:¶
* Pages with unreviewed LWG DR marker
2024.06.10 | http://cppreference.com |