— Scheme Procedure: proper-list? obj

Return #t if obj is a proper list, or #f otherwise. This is the same as the core list? (see List Predicates).

A proper list is a list which ends with the empty list () in the usual way. The empty list () itself is a proper list too.

          (proper-list? '(1 2 3))  => #t
          (proper-list? '())       => #t
     

— Scheme Procedure: circular-list? obj

Return #t if obj is a circular list, or #f otherwise.

A circular list is a list where at some point the cdr refers back to a previous pair in the list (either the start or some later point), so that following the cdrs takes you around in a circle, with no end.

          (define x (list 1 2 3 4))
          (set-cdr! (last-pair x) (cddr x))
          x => (1 2 3 4 3 4 3 4 ...)
          (circular-list? x)  => #t
     

— Scheme Procedure: dotted-list? obj

Return #t if obj is a dotted list, or #f otherwise.

A dotted list is a list where the cdr of the last pair is not the empty list (). Any non-pair obj is also considered a dotted list, with length zero.

          (dotted-list? '(1 2 . 3))  => #t
          (dotted-list? 99)          => #t
     

— Scheme Procedure: null-list? lst

Return #t if lst is the empty list (), #f otherwise. If something else than a proper or circular list is passed as lst, an error is signalled. This procedure is recommended for checking for the end of a list in contexts where dotted lists are not allowed.

— Scheme Procedure: not-pair? obj

Return #t is obj is not a pair, #f otherwise. This is shorthand notation (not (pair? obj)) and is supposed to be used for end-of-list checking in contexts where dotted lists are allowed.

— Scheme Procedure: list= elt= list1 ...

Return #t if all argument lists are equal, #f otherwise. List equality is determined by testing whether all lists have the same length and the corresponding elements are equal in the sense of the equality predicate elt=. If no or only one list is given, #t is returned.