79 lines
1.9 KiB
Markdown
79 lines
1.9 KiB
Markdown
# 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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`apply` will let you pass arguments to a function, as will `fun.(args)`
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## Running tests
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Execute the tests with:
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```bash
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$ elixir strain_test.exs
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```
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### Pending tests
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In the test suites, all but the first test have been skipped.
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Once you get a test passing, you can unskip the next one by
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commenting out the relevant `@tag :pending` with a `#` symbol.
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For example:
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```elixir
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# @tag :pending
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test "shouting" do
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assert Bob.hey("WATCH OUT!") == "Whoa, chill out!"
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end
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```
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Or, you can enable all the tests by commenting out the
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`ExUnit.configure` line in the test suite.
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```elixir
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# ExUnit.configure exclude: :pending, trace: true
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```
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For more detailed information about the Elixir track, please
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see the [help page](http://exercism.io/languages/elixir).
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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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