Hi Mikael,
Mikael Djurfeldt <mik...@djurfeldt.com> writes:
> I'm working on an mit-scheme compatibility module (compat mit-scheme)
> enabling Guile to read a (so far) subset of mit-scheme code.
>
> Now I have the problem that mit-scheme has the two constants
> #!optional and #!rest (mit-scheme extensions to the scheme standard).
>
> I thought that I could support this using %read-hash-procedures but
> discovered that there are three "precedence levels":
>
> 1. Most predefine hash syntax like #(, #! etc.
> 2. %read-hash-procedures
> 3. #|
>
> This means that I can't add new syntax for #!.
>
> I propose to simplify this to only two levels:
>
> 1. %read-hash-procedures
> 2. predefined syntax
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.
One idea would be to provide a way to register new handlers for tokens
of the form "#!<symbol><delimiter>". However, we'd probably want to
discourage its use, because every time you add a new token, you
potentially turn existing #! ... !# block comments into lexical errors.
Thanks for working on scmutils for Guile!
I've been wanting this for a while :)
Mark
