CODEWITHSUNDEEP
c++arraysc++11
Amr Rady
Amr Rady

Reputation: 1197

How to use std::for_each over std::array<> and apply lambda function on each element?

I want to combine these three features together:

into one example using C++11.

std::for_each(arr, arr + sizeof(arr) / sizeof(int), [&](int x) { std::cout<<x<<" ";});

How to convert that code to operate over std::array ?

Upvotes: 3

Views: 4962

Answers (2)

gsamaras
gsamaras

Reputation: 73444

You want array::begin and array::end of the array, for the two first parameters of for_each(), which will mark the start and end of the array.

Then the third parameter is a function, in your case a lambda function, like this:

std::for_each(myarray.begin(), myarray.end(), [](int x) { std::cout << x <<" "; });

PS: For a more generic approach, you could use std::begin() and std::end(), so that if the container changes (from std::array to std::vector for example), you can keep this code unchanged.

Upvotes: 6

duong_dajgja
duong_dajgja

Reputation: 4276

The answer is quite popular on the internet. I grabbed from std::array in action

Given:

std::array<int, 8> arr{1, 2, 3, 4, 5, 6, 7, 8};

Or even:

int arr[] = {1, 2, 3, 4, 5, 6, 7, 8};

Use of for_each and lambda:

std::for_each(std::begin(arr), std::end(arr), [](int v){std::cout << v << " ";});

or even:

// calculate the sum of the array by using a global variable
int sum = 0;
std::for_each(std::begin(arr), std::end(arr), [&sum](int v) { sum += v; });
std::cout << "sum of array{1,2,3,4,5,6,7,8}: " << sum << std::endl;

Updated

Using std::begin() and std::end() instead of .begin() and .end() as suggested by @NathanOliver.

Upvotes: 0

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