Re: [Chicken-hackers] [PATCH] Fix meta evaluation (so that require-extension-for-syntax works properly)

[John Cowan]

Peter Bex scripsit:

> This means that currently we can only get syntax-rules from R7RS
> through (import-for-syntax r7rs), because it's on the right-hand side
> of define-syntax.

Well, that's not so bad, or wouldn't be so bad if there was a command-line
switch to accomplish it.

> You can't truly ignore it, except maybe by hacking around it by making
> syntax-rules a part of define-syntax and friends, and allowing no
> other macro expander types.

Within the R7RS-small context, that would actually work, since no other
syntax transformer is allowed in conforming R7RS code.  But frankly I'd
rather you just put a formal derogation saying that Chicken supports
only R5RS syntax-rules even in R7RS mode.  After all, Chibi supports
R7RS syntax-rules even in its R5RS (default) mode.

> As much as I hate to say it, the explicit phasing stuff in R6RS really
> seems like the Right Way to do it.  

See <http://www.cs.indiana.edu/~dyb/pubs/implicit-phasing.pdf>,
which explains the advantages of implicit phasing.  It's
actually possible to write libraries which are valid on an
implicit-phasing system but not on an explicit-phasing system.
As far as I know, Andre van Tonder is the only actual convert
from the explicit-phasing faith to the implicit-phasing faith
(most people adopt one or the other right away), so his email at
<http://lists.r6rs.org/pipermail/r6rs-discuss/2009-September/005493.html>
is worth reading too.

-- 
Real FORTRAN programmers can program FORTRAN    John Cowan
in any language.  --Ed Post                     address@hidden