Does the CL spec require the implementation to use linked lists or merely to behave as if it were a linked list? I believe it is the latter and that makes a wor

Does the CL spec require the implementation to use linked lists or merely to behave as if it were a linked list? I believe it is the latter and that makes a world of difference when it comes to optimization. A great mainstream example of this are JavaScript Arrays. They are defined to behave as hashtables. They inherit from Object. Their "indices" are actually strings instead of numbers (all object keys are strings and numbers get converted to strings before the lookup happens). Despite that spec model, JS arrays have used a very different representation in practice for decades. Even in the dark ages, arrays were implemented as linked lists. Today, they might be hashtables, linked lists, boxed objects, or even unboxed primitives all while still pretending to be hashtables. Cons doesn't have to return a linked list element.