From: "Drew Adams" <drew.adams@oracle.com>
To: "'Thierry Volpiatto'" <thierry.volpiatto@gmail.com>
Cc: 11328@debbugs.gnu.org
Subject: bug#11328: 24.1.50; Comment in `dired-copy-file-recursive' code
Date: Thu, 26 Apr 2012 07:09:06 -0700 [thread overview]
Message-ID: <0A995EE899D2417E8DDD481A153E96BF@us.oracle.com> (raw)
In-Reply-To: <87ipgngi26.fsf@gmail.com>
> we can't say also they are really "free" (even if they
> are sort of free) because they are (will be) all
> let-bounded in some places.
Look up the definition of free variable - see the lambda calculus.
It is always about free _occurrences_ of a variable. Freedom of a variable (not
a great word for it, admittedly) is relative to a given context.
Whether a variable is bound in some outer lambda is not the question. What
matters is whether it is free in some other (e.g. inner) lambda.
X is a free variable in the inner lambda form here, though it is bound in the
outer one, i.e., in the overall expression.
(funcall
(funcall
(lambda (x) (lambda (y) (+ x y)))
42) ; Fn that increments by 42.
3) ; Applied to 3 gives 45.
That is equivalent to this:
(let ((x 42))
(funcall (lambda (y) (+ x y)) 3)
(It's perhaps clearer if you remove all the `funcall' atoms. That will give you
Lisp 1 syntax ~= lambda calculus syntax.)
next prev parent reply other threads:[~2012-04-26 14:09 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-24 17:37 bug#11328: 24.1.50; Comment in `dired-copy-file-recursive' code Drew Adams
2012-04-24 17:49 ` Drew Adams
2012-04-24 18:22 ` Drew Adams
2012-04-25 13:40 ` Nix
2012-04-25 16:26 ` Drew Adams
2012-04-25 18:42 ` Thierry Volpiatto
2012-04-25 21:51 ` Drew Adams
2012-04-26 5:48 ` Thierry Volpiatto
2012-04-26 14:09 ` Drew Adams [this message]
2012-04-26 15:35 ` Drew Adams
2012-04-26 18:38 ` Thierry Volpiatto
2012-04-24 18:54 ` Stefan Monnier
2014-02-09 4:32 ` Lars Ingebrigtsen
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