Subject: Scheme's "apply" [was: Re: Adding a charcter ... ]
From: (Rob Warnock)
Date: 1 Nov 2000 04:57:21 GMT
Newsgroups: comp.lang.lisp
Message-ID: <8to7rh$ahn7d$>
Erik Naggum  <> wrote:
| (apply #'concatenate 'string (mapcar #'string list))
|   If you have a Scheme background (where apply takes two arguments),
|   you could have consed 'string onto the list of arguments, too.

Erik, just as Lisp has evolved beyond the outdated concepts of
"interpreter/slow/etc." and Common Lisp has evolved beyond CLtL1,
Scheme too has made *some* progress over its life, and in fact has
had multi-arg "apply" since at least 1986 with the release of R3RS.

Granted, in R3RS and R4RS the two-arg form was called an "essential
procedure" and the multi-arg form was just a "procedure", but by the
time of the IEEE Scheme Standard in 1991 (and in R5RS today), this
distinction had vanished:

	(apply proc arg1 ... args)

	Proc must be a procedure and args must be a list. Calls proc
	with the elements of the list (append (list arg1 ...) args)
	as the actual arguments.

For example:

	> (apply vector 1 2 3 '(4 5 6))
	#(1 2 3 4 5 6)
	> (apply string-append (map string '(#\a #\c #\e) '(#\b #\d #\f)))


Rob Warnock, 31-2-510
Network Engineering
Silicon Graphics, Inc.		Phone: 650-933-1673
1600 Amphitheatre Pkwy.		PP-ASEL-IA
Mountain View, CA  94043