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Re: [Chicken-hackers] Made a start with CHICKEN 5 proposal

From: Alex Shinn
Subject: Re: [Chicken-hackers] Made a start with CHICKEN 5 proposal
Date: Tue, 9 Sep 2014 20:02:38 +0900

On Tue, Sep 9, 2014 at 5:57 AM, Peter Bex <address@hidden> wrote:

- The "new" syntax-rules foolishly changed the underscore to act as
   a wildcard symbol, making it - strictly speaking - incompatible with
   R5RS.  I don't think it's a good idea to support this in core.

I think this has been discussed here before, but it's R6RS
which is incompatible and breaks many macros here.  R7RS
"fixed" this for basically all realistic cases by requiring that
using _ as a literal overrides the wildcard behavior.

- For no good reason, R7RS syntax-rules allows not only renaming
   ellipsis identifiers, but also quoting them (which I think is
   a bit ugly).  I *think* this is entirely backwards compatible,
   so we could add that to core.

The ellipsis renaming (and also already supported by Chicken tail
patterns) are just Taylor Campbell's SRFI 46.  It makes many
macros more readable than (... <x>) escaping.  The latter, however,
is very widely supported.  Probably providing both forms of
escape was overkill, but these are easy to implement and entirely
backwards compatible.


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