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.

Adding method to the Array structure

This exercise focuses on adding methods to the Array structure in Swift. This is easiest done through using extensions.

extension Array {
  // Write your code for the 'Strain' exercise in this file.
}

The Array documentation can be found here.

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Source

Conversation with James Edward Gray II