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nreverse 368
I
nreverse sequence Function
nreverse returns a sequence containing the same elements as sequence, but
in reverse order. The result mayor may not be eq to the argument, so it
is usually wise to say something like (setq x (nreverse x», because
(nreverse x) is not guaranteed to leave the reversed value in x.
sequence can be either a list or a vector (one-dimensional array). Note that
nil is considered to be a sequence, of length zero.
For example:
(setq item-list '(heron stork loon owl»
=> (HERON STORK LOON OWL)
(nreverse item-list) => (OWL LOON STORK HERON)
item-list => (HERON)
nreverse is the destructive version of reverse.
For a table of related items: See the section "Functions for Modifying
Lists" in Symbolics Common Lisp: Language Concepts.
For a table of related items: See the section "Sequence Modification" in
Symbolics Common Lisp: Language Concepts.
zl:nreverse list Function
zl:nreverse reverses its argument, which should be a list. The argument
is destroyed by rplacds all through the list (see zl:reverse). Example:
(zl :nreverse '(a b c» => (c b a)
zl:nreverse could have been defined by:
(de fun nreverse (x)
(cond «null x) nil)
«nreverse1 x nil»»
(de fun nreverse1 (x y)
; auxiliary function
(cond «null (cdr x» (rplacd x y»
«nreverse1 (cdr x) (rplacd x y»»)
;; this last call depends on order of argument evaluation.
zl:nreverse does something inefficient with cdr-coded lists, because it just
uses rplacd in the straightforward way. See the section "Cdr-Coding" in
Symbolics Common Lisp: Language Concepts. Using zl:reverse might be
preferable in some cases.
For a table of related items: See the section "Functions for Modifying
Lists" in Symbolics Common Lisp: Language Concepts.