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mryan's solution

to Accumulate in the Raku Track

Published at Mar 26 2021 · 0 comments
Test suite

Implement the accumulate operation, which, given a collection and an operation to perform on each element of the collection, returns a new collection containing the result of applying that operation to each element of the input collection.

Given the collection of numbers:

  • 1, 2, 3, 4, 5

And the operation:

  • square a number (x => x * x)

Your code should be able to produce the collection of squares:

  • 1, 4, 9, 16, 25

Check out the test suite to see the expected function signature.


Keep your hands off that collect/map/fmap/whatchamacallit functionality provided by your standard library! Solve this one yourself using other basic tools instead.


Remember to check out the Raku documentation and resources pages for information, tips, and examples if you get stuck.

Running the tests

There is a test suite and module included with the exercise. The test suite (a file with the extension .rakutest) will attempt to run routines from the module (a file with the extension .rakumod). Add/modify routines in the module so that the tests will pass! You can view the test data by executing the command raku --doc *.rakutest (* being the name of the test suite), and run the test suite for the exercise by executing the command prove6 . in the exercise directory.


Conversation with James Edward Gray II https://twitter.com/jeg2

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.


#!/usr/bin/env raku
use Test;
use lib $?FILE.IO.dirname;
use Accumulate;
plan 6;

  accumulate( [], -> {} ),
  'test empty';

  accumulate( 1..5, *² ),
  [1, 4, 9, 16, 25],
  'raise to 2';

    (10, 17, 23),
    { $^a div 7, $a % 7 }
  [ (1, 3), (2, 3), (3, 2) ],

  accumulate( <hello exercism>, *.uc ),

    <a b c>,
    -> $letter {
      ( accumulate 1..3, { $letter ~ $^number } )
  [ [<a1 a2 a3>], [<b1 b2 b3>], [<c1 c2 c3>] ],

  accumulate( <the quick brown fox>, *.flip ),
  [<eht kciuq nworb xof>],
  'reverse strings';
unit module Accumulate;

sub accumulate ( @list, &function ) returns Array() is export {
	@list.map: &function

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