65 lines
1.8 KiB
Markdown
65 lines
1.8 KiB
Markdown
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# Strain
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Implement the `keep` and `discard` operation on collections. Given a collection
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and a predicate on the collection's elements, `keep` returns a new collection
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containing those elements where the predicate is true, while `discard` returns
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a new collection containing those elements where the predicate is false.
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For example, given the collection of numbers:
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- 1, 2, 3, 4, 5
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And the predicate:
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- is the number even?
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Then your keep operation should produce:
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- 2, 4
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While your discard operation should produce:
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- 1, 3, 5
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Note that the union of keep and discard is all the elements.
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The functions may be called `keep` and `discard`, or they may need different
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names in order to not clash with existing functions or concepts in your
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language.
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## Restrictions
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Keep your hands off that filter/reject/whatchamacallit functionality
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provided by your standard library! Solve this one yourself using other
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basic tools instead.
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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 strain_test.rb
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To include color from the command line:
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ruby -r minitest/pride strain_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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