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  ANSI Common Lisp   14 Conses   14.1 Cons Concepts

14.1.2 Conses as Lists

A list is a chain of conses in which the car of each cons is an element of the list, and the cdr of each cons is either the next link in the chain or a terminating atom.

A proper list is a list terminated by the empty list. The empty list is a proper list, but is not a cons.

An improper list is a list that is not a proper list; that is, it is a circular list or a dotted list.

A dotted list is a list that has a terminating atom that is not the empty list. A non-nil atom by itself is not considered to be a list of any kind - not even a dotted list.

A circular list is a chain of conses that has no termination because some cons in the chain is the cdr of a later cons.

Some defined names relating to lists.
append last nbutlast rest
butlast ldiff nconc revappend
copy-alist list ninth second
copy-list list* nreconc seventh
eighth list-length nth sixth
endp make-list nthcdr tailp
fifth member pop tenth
first member-if push third
fourth member-if-not pushnew  Lists as Association Lists  Lists as Sets  General Restrictions on Parameters that must be Lists

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