75 lines
2.0 KiB
Markdown
75 lines
2.0 KiB
Markdown
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# Accumulate
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Implement the `accumulate` operation, which, given a collection and an
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operation to perform on each element of the collection, returns a new
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collection containing the result of applying that operation to each element of
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the input collection.
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Given the collection of numbers:
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- 1, 2, 3, 4, 5
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And the operation:
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- square a number (`x => x * x`)
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Your code should be able to produce the collection of squares:
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- 1, 4, 9, 16, 25
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Check out the test suite to see the expected function signature.
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## Restrictions
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Keep your hands off that collect/map/fmap/whatchamacallit functionality
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provided by your standard library!
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Solve this one yourself using other basic tools instead.
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## Advanced
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It is typical to call [#to_enum](http://ruby-doc.org/core-2.3.1/Object.html#method-i-to_enum) when defining methods for a generic Enumerable, in case no block is passed.
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Here is an additional test you could add:
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```ruby
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def test_accumulate_when_block_is_deferred
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skip
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accumulate_enumerator = [1, 2, 3].accumulate
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accumulated_result = accumulate_enumerator.each do |number|
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number * number
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end
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assert_equal [1, 4, 9], accumulated_result
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end
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```
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* * * *
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For installation and learning resources, refer to the
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[exercism help page](http://exercism.io/languages/ruby).
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For running the tests provided, you will need the Minitest gem. Open a
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terminal window and run the following command to install minitest:
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gem install minitest
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If you would like color output, you can `require 'minitest/pride'` in
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the test file, or note the alternative instruction, below, for running
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the test file.
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Run the tests from the exercise directory using the following command:
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ruby accumulate_test.rb
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To include color from the command line:
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ruby -r minitest/pride accumulate_test.rb
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## Source
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Conversation with James Edward Gray II [https://twitter.com/jeg2](https://twitter.com/jeg2)
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## Submitting Incomplete Solutions
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It's possible to submit an incomplete solution so you can see how others have completed the exercise.
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