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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.
In order to run the test, you can run the test file from the exercise
directory. For example, if the test suite is called
`hello_world_test.rb`, you can run the following command:
ruby hello_world_test.rb
To include color from the command line:
ruby -r minitest/pride hello_world_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
102 entries across 102 versions & 1 rubygems