• nconc &rest lists → concatenated-list

• list - each but the last must be a list (which might be a dotted list but must not be a circular list); the last list may be any object.
• concatenated-list - a list.

Returns a list that is the concatenation of lists. If no lists are supplied, (nconc) returns nil. nconc is defined using the following recursive relationship:

(apply #'nconc nil lists) ≡ (apply #'nconc lists)
(nconc list-1 list-2) ≡ (progn (rplacd (last list-1) list-2) list-1)
(apply #'nconc list-1 list-2 lists) ≡ (apply #'nconc (nconc list-1 list-2) lists)

(nconc) 

→

NIL



(nconc (list 'foo 'bar 'baz))) 

→

(FOO BAR BAZ)



(defparameter *x* '(a b c)) 

→

(A B C)



(defparameter *y* '(d e f)) 

→

(D E F)



(nconc *x* *y*) 

→

(A B C D E F)



*x* 

→

(A B C D E F)

Note, in the example, that the value of *x* is now different, since its last cons has been rplacd'd to the value of *y*. If (nconc *x* *y*) were evaluated again, it would yield a piece of a circular list, whose printed representation would be (A B C D E F D E F D E F ...), repeating forever; if the *print-circle* switch were non-nil, it would be printed as (A B C . #1=(D E F . #1#)).

(defparameter *foo* (list 'a 'b 'c 'd 'e)) 

→

*FOO*



(defparameter *bar* (list 'f 'g 'h 'i 'j)) 

→

*BAR*



(defparameter *baz* (list 'k 'l 'm)) 

→

*BAZ*



(setf *foo* (nconc *foo* *bar* *baz*)) 

→

(A B C D E F G H I J K L M)



*foo* 

→

(A B C D E F G H I J K L M)



*bar* 

→

(F G H I J K L M)



*baz* 

→

(K L M)



(setf *foo* (list 'a 'b 'c 'd 'e) 

→

(A B D C E)



(setf *bar* (list 'f 'g 'h 'i 'j)) 

→

(F G H I J)



(setf *baz* (list 'k 'l 'm)) 

→

(K L M)



(setf *foo* (nconc nil *foo* *bar* nil *baz*)) 

→

(A B C D E F G H I J K L M) 



*foo* 

→

(A B C D E F G H I J K L M)



*bar* 

→

(F G H I J K L M)



*baz* 

→

(K L M)

The lists are modified rather than copied.

None.

None.

Function APPEND, Function CONCATENATE

To be done.

None.

\issue{REMF-DESTRUCTION-UNSPECIFIED:X3J13-MAR-89} \issue{DOTTED-LIST-ARGUMENTS:CLARIFY}