Strain

Instructions

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.

Implementaton Notes

The test suite passes a Function class instance to the keep and discard methods as a block argument. To successfully pass the tests, you'll need to call that function inside your code. If you're unfamiliar with how to do this, please consult the Function class documentation.

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Source

Conversation with James Edward Gray II