From: Josef Wolf <jw@raven.inka.de>
To: guile-user@gnu.org
Subject: Re: Need help with a macro
Date: Mon, 16 Nov 2009 18:20:45 +0100 [thread overview]
Message-ID: <20091116172045.GE29831@raven.wolf.lan> (raw)
In-Reply-To: <87lji7h6ul.fsf@ossau.uklinux.net>
On Sun, Nov 15, 2009 at 08:26:58PM +0000, Neil Jerram wrote:
> Josef Wolf <jw@raven.inka.de> writes:
> > I am trying to work through the little schemer book. In order to make it
> > easier to go through the examples, I've come up with the following macro:
> > [ ... ]
>
> The body of a define-macro definition is supposed to return the code
> that should be substituted in place of the original macro call. With
> the newlines there, the body returns *unspecified*, because that is what
> (newline) returns.
OK, I think I see the problem now...
> Do you want those newlines to happen at macro-expansion time or eval
> time? If the latter (which I would guess), the code that you want is
>
> (define-macro (disp exp)
> (display exp) (newline)
> `(begin
> (display ,exp)
> (newline) (newline)))
Works great. Thanks!
prev parent reply other threads:[~2009-11-16 17:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-15 16:33 Need help with a macro Josef Wolf
2009-11-15 18:18 ` Andy Wingo
2009-11-16 17:40 ` Josef Wolf
2009-11-15 20:26 ` Neil Jerram
2009-11-16 17:20 ` Josef Wolf [this message]
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