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Code sugar and high-level concepts

Let us multiply all the elements from the set {1, 2, 13} by all the elements of {7, 5}.
Thinking in imperative languages, one may come with two nested loops (or iterators).

Speaking C++
#include <iostream>

using namespace std;

int main() {
    int a [] = {1, 2, 13};
    int b [] = {7, 5};
    for (int i = 0; i < 3; ++i) {
        for (int j = 0; j < 3; ++j) {
            cout << a[i] * b[j] << endl;
    return 0;

In Python I'd rather utilize a list comprehension
>>>  [a * b for a in [1, 2, 13] for b in [7, 5]]

The same goes to the blocks in ruby
> [1, 2, 13].each do |x| [7, 5].each { |y| puts x * y } end

One may find analogous list comprehensions in Haskell. But they aren't cool here.
All you need is applicative functors aka Control.Applicative
(*) <$> [1,2,13] <*> [7,5]

Bonus: have you noticed, the C++ code contains a bug which is passed by the compiler? There are only two elements in array b, not three! The practical consequence of high-level concepts: cleaner code for less debugging.


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