Course of Raku / Addendum 🆕 / Flow and functions / Subroutines and functional style / Exercises / Sum of even squares

Solution: Sum of even squares

Here is a possible solution to the task.

Code

say [+] (1..10).grep(* %% 2).map(* ** 2);

🦋 You can find the source code in the file sum-even-squares.raku.

Output

220

Comments

1. The chain reads left to right: .grep(* %% 2) keeps the even numbers, .map(* ** 2) squares each, and [+] reduces the squares to their sum.

2. The even numbers 2 4 6 8 10 square to 4 16 36 64 100, which add up to 220.

3. The same steps can be written as a feed pipeline, where ==> passes each result on to the next stage — so the flow reads top to bottom rather than as a method chain:

   (1..10)
       ==> grep(* %% 2)
       ==> map(* ** 2)
       ==> sum()
       ==> say();

   Each ==> feeds its left-hand list into the next routine, and the final ==> say() prints the total, 220.

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