From: Leo <sdl.web@gmail.com>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: emacs-devel@gnu.org
Subject: Re: Common Lisp like feature expressions
Date: Tue, 28 Dec 2010 15:26:31 +0000 [thread overview]
Message-ID: <m1vd2d6hqw.fsf@cam.ac.uk> (raw)
In-Reply-To: <jwvpqsmn2be.fsf-monnier+emacs@gnu.org> (Stefan Monnier's message of "Mon, 27 Dec 2010 20:01:02 -0500")
On 2010-12-28 01:01 +0000, Stefan Monnier wrote:
> Just for fun, here's a version using pcase:
>
> (defun eval-feature-expression (form)
> (pcase form
> ((pred atom) (featurep form nil))
> (`(not ,x) (not (eval-feature-expression x)))
> (`(and) t)
> (`(and ,form1 . ,forms)
> (and (eval-feature-expression form1)
> (eval-feature-expression (cons 'and forms))))
> (`(or) nil)
> (`(or ,form1 . ,forms)
> (or (eval-feature-expression form1)
> (eval-feature-expression (cons 'or forms))))
> (t (error "Invalid feature expression: %s" form)))))
That appears to be an excellent example for pcase. Maybe it should be
added to the header of pcase.el or where it is documented? Thanks.
Leo
prev parent reply other threads:[~2010-12-28 15:26 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-27 9:21 How and when to use GCPRO? Leo
2010-12-27 10:15 ` Andreas Schwab
2010-12-27 10:38 ` Leo
2010-12-27 11:17 ` Andreas Schwab
2010-12-27 16:00 ` Stefan Monnier
2010-12-27 17:51 ` Andreas Schwab
2010-12-28 1:01 ` Stefan Monnier
2010-12-28 1:33 ` Daniel Colascione
2010-12-28 2:17 ` Stefan Monnier
2010-12-28 3:37 ` Daniel Colascione
2010-12-28 4:15 ` Stefan Monnier
2010-12-28 4:36 ` Conservative scanning (was: Re: How and when to use GCPRO?) Daniel Colascione
2010-12-28 17:07 ` How and when to use GCPRO? Richard Stallman
2010-12-27 19:15 ` Leo
2010-12-27 19:26 ` Common Lisp like feature expressions (was: How and when to use GCPRO?) Leo
2010-12-27 19:38 ` Andreas Schwab
2010-12-27 19:57 ` Leo
2010-12-28 1:01 ` Common Lisp like feature expressions Stefan Monnier
2010-12-28 15:26 ` Leo [this message]
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