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Contents
# Strain
Implement the `keep` and `discard` operation on collections. Given a collection
and a predicate on the collection's elements, `keep` returns a new collection
containing those elements where the predicate is true, while `discard` returns
a new collection containing those elements where the predicate is false.
For example, given the collection of numbers:
- 1, 2, 3, 4, 5
And the predicate:
- is the number even?
Then your keep operation should produce:
- 2, 4
While your discard operation should produce:
- 1, 3, 5
Note that the union of keep and discard is all the elements.
The functions may be called `keep` and `discard`, or they may need different
names in order to not clash with existing functions or concepts in your
language.
## Restrictions
Keep your hands off that filter/reject/whatchamacallit functionality
provided by your standard library! Solve this one yourself using other
basic tools instead.
* * * *
For installation and learning resources, refer to the
[exercism help page](http://exercism.io/languages/ruby).
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 strain_test.rb
To include color from the command line:
ruby -r minitest/pride strain_test.rb
## Source
Conversation with James Edward Gray II [https://twitter.com/jeg2](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.
Version data entries
79 entries across 79 versions & 1 rubygems