exercism/ruby/accumulate/README.md

Accumulate

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.

Restrictions

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

Advanced

It is typical to call #to_enum when defining methods for a generic Enumerable, in case no block is passed.

Here is an additional test you could add:

def test_accumulate_when_block_is_deferred
  skip
  accumulate_enumerator = [1, 2, 3].accumulate
  accumulated_result = accumulate_enumerator.each do |number|
    number * number
  end
  assert_equal [1, 4, 9], accumulated_result
end

---

For installation and learning resources, refer to the exercism help page.

For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:

gem install minitest

If you would like color output, you can require 'minitest/pride' in the test file, or note the alternative instruction, below, for running the test file.

Run the tests from the exercise directory using the following command:

ruby accumulate_test.rb

To include color from the command line:

ruby -r minitest/pride accumulate_test.rb

Source

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.