Re: Precedence for reader extensions

[Mikael Djurfeldt]

On Tue, Feb 19, 2013 at 12:33 AM, Mark H Weaver <address@hidden> wrote:
> Mikael Djurfeldt <address@hidden> writes:
>> I propose to simplify this to only two levels:
>>
>> 1. %read-hash-procedures
>> 2. predefined syntax

It turns out that the change I propose above was already implemented
in read.c.  The effect just wasn't visible due to a bug in flush_ws
which caused all #! to be erroneously removed if they exist as the
outermost expression.

In the attached diff, I've fixed the flush_ws bug and cleaned up some
garbage code in scm_read_sharp which was unreachable.

Can I push this into the repository?

> I don't think this would be sufficient.  The problem is that tokens of
> the form "#!<symbol><delimiter>" have become standardized.  To name a
> few examples, both R6RS and R7RS define the reader directives
> #!fold-case and #!no-fold-case, R6RS has #!r6rs, and SRFI-105 has
> #!curly-infix.  Guile also has #! ... !# block comments to help with the
> handling of executable scripts.

In what sense is it not sufficient?  In any case: The present diff
doesn't remove any functionality or make performance worse.  It only
removes some inconsistent behavior.  At the same time it allows
support for mit-scheme #!optional and #!rest.

Best regards,
Mikael D.

reader-fix.diff
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