Conses as Lists (ANSI and GNU Common Lisp Document)

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#### 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.

      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

      Figure 14–3: Some defined names relating to lists.