[kazinator]

A simple deque in the spirit of unencapsulated lists can be made in Common Lisp using two back-to back lists. So that is to say, each end of the deque is a Lisp list, where we chase cdr going toward the middle of the deque.

Only the pop operation has to know about the arrangement. We make it a macro which cleverly transfers nodes from one list to the other to keep the amortized cost low.

https://www.kylheku.com/cgit/lisp-snippets/tree/deque.lisp [oops, where are the test cases?]

> That does not mean that I should think everything in the language or everything that people commonly use are good ideas.

I, however, provide the "cadavers" down to one level deeper in TXR Lisp than Common Lisp, from caar to cdddddr. Therefore, I'm not in a position to turn around and disown them as a bad idea.

There are people genuinely invested in various aspects of this stuff.