The core collections in Swift are single, simple, non-abbreviated, real English words:
Array, Set, Dictionary, String
Conversely, collections that we don’t expect people to write out themselves have more lengthy, jargony, compound names:
DropFirstSequence, LazyFilterSequence, Zip2Sequence, etc.
This latter group generally arises as the return type of methods which transform existing collections, whereas the first group is often used directly with the type-name written out by the user.
It seems evident that double-ended queues are designed to be used directly, and they are not simply the result of transforming an existing collection.
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Regarding the term Deque, if I may put my own experience as an anecdote, my degree is in math but I also minored in computer science so I took all the basic CS courses including data structures and algorithms.
I remember learning about queues and double-ended queues in class, and the latter were sometimes shortened to “dequeue”. However I never encountered the spelling “deque” at all in school.
I’m not sure if I’ve seen it since then either. I like to read published articles on efficient implementations of data structures and algorithms, but still I can’t remember seeing “deque” in any context.
So I would say, for myself, that “deque” is emphatically not a term of art that I would recognize.