cons package:mono-traversable

Prepend an element onto a sequence.

> 4 `cons` [1,2,3]
[4,1,2,3]

Prepend an element to a SemiSequence, creating a non-null SemiSequence. Generally this uses cons underneath. cons is not efficient for most data structures. Alternatives:

• if you don't need to cons, use fromNullable or nonNull if you can create your structure in one go.
• if you need to cons, you might be able to start off with an efficient data structure such as a NonEmpty List. fromNonEmpty will convert that to your data structure using the structure's fromList function.

Extract the first element of a sequence and the rest of the non-null sequence if it exists.

Use Data.List's : to prepend an element to a sequence.

uncons returns the tuple of the first element of a sequence and the rest of the sequence, or Nothing if the sequence is empty.

> uncons (fromList [1,2,3,4] :: Vector Int)
Just (1,fromList [2,3,4])

> uncons ([] :: [Int])
Nothing