From: John Cowan <[email protected]>
Subject: Re: [r6rs-discuss] Import choices: flexibility vs. discoverability
Date: Tue, 13 Oct 2009 17:21:24 -0400
> Shiro Kawai scripsit:
>
> > Hmm... in this scenario, you can only say (import Good-Module)
> > within some conditionals, either directly in the cond-expand
> > clause or indirectly within the included file. That means
> > import must be recognized *after* macro expansion, or the
> > conditional must be lifted to the module-syntax level, doesn't it?
>
> No, because you import the same set of identifiers in either case.
> You load different sets of code thanks to the conditional inclusion.
I don't understand. My application can work with and without
Good-Module, but wants to use it if available.
Somewhere in my app I need to say (import Good-Module) in
order to use existing Scheme module Good-Module, right?
Do you suggest that I put (import Good-Module) in a file and
include it in conditional clause? e.g.
(cond-expand
(has-good-module (include "import-good-module.scm"))
(else ...alternative code...))
and in separate file "import-good-module.scm"
(import Good-Module)
But if include just works as code substitution, then isn't the
above code equivalent to the following?
(cond-expand
(has-good-module (import Good-Module))
(else ...alternative code...))
--shiro
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