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Re: [Chicken-users] How to avoid predefined cond-expand features in csc?
From: |
Peter Bex |
Subject: |
Re: [Chicken-users] How to avoid predefined cond-expand features in csc? |
Date: |
Mon, 28 Dec 2015 14:19:10 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, Dec 28, 2015 at 09:32:24AM +0100, Sven Hartrumpf wrote:
> PB wrote on 2015-12-24 11:25:
> > These features are a bit weird: when you require a core library, it will
> > register a feature with the same name (I think that's to prevent it from
> > being reloaded again). I'm not sure if this is in general for units or
> > only for core units, but I think the problem here is that the compiler
> > loads all of them. So you're really cond-expanding against what's
> > been loaded by the compiler, which is of course undocumented and subject
> > to change.
>
> And hopefully is changed ... in chicken 5? :-)
There are plans to overhaul the whole unit/module/library loading stuff,
but development on CHICKEN 5 seems to have stalled a bit. We need more
people to work on it, even if just to flesh out the desired API.
> >> Example:
> >> > echo "(cond-expand (srfi-1 (print "srfi-1")) (else))" > bugchicken2.scm
> >> > csi -e '(load "bugchicken2.scm")'
> >> > -> as expected
> >> > csc bugchicken2.scm && ./bugchicken2
> >> srfi-1 -> unexpected; csc should behave like csi.
> >
> > If you don't mind doing this at runtime, that's a solution:
> >
> > (when (feature? srfi-1:) (print "srfi-1"))
>
> Thanks for the idea.
> But I need cond-expand mainly to write programs that are portable
> across different Scheme implementation. So I cannot replace the
> most basic SRFI-0 by some implementation-specific variant.
You could still do something like
(cond-expand
(chicken (when (feature? srfi-1:) (print "srfi-1")))
(gauche ...)
(chibi ...)
(else ...))
It's not pretty but it should do the trick. You could even write a
macro that expands to the desired cond-expand form, but that's a bit
tricky to do if you can't rely on syntax-rules being present.
Cheers,
Peter
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