EndsWith

[Source | Tests]

This function checks whether the final elements of the one collection are the same as the elements in another collection.

## Detailed Design

The `ends(with:)` and `ends(with:by:)` functions are added as methods on an extension of 
`BidirectionalCollection`.

```swift
extension BidirectionalCollection {
    public func ends<PossibleSuffix: BidirectionalCollection>(
        with possibleSuffix: PossibleSuffix
    ) -> Bool where PossibleSuffix.Element == Element
    
    public func ends<PossibleSuffix: BidirectionalCollection>(
        with possibleSuffix: PossibleSuffix,
        by areEquivalent: (Element, PossibleSuffix.Element) throws -> Bool
    ) rethrows -> Bool
}

This method requires BidirectionalCollection for being able to traverse back from the end of the collection. It also requires the possibleSuffix to be BidirectionalCollection, because it too needs to be traverse backwards, to compare its elements against self from back to front.

Complexity

O(m), where m is the lesser of the length of the collection and the length of possibleSuffix.

Naming

The function's name resembles that of an existing Swift function starts(with:), which performs same operation however in the forward direction of the collection.