Re: Four problems with Scheme 48 1.8

Thanks for your message!


On Tuesday 14 Jul 2009 13:09, you wrote:

> > (2) I cannot figure out how to define a macro such as:
> >
> > (defmacro substr (str from . rest)
> >   (if (null? rest)
> >       ; two argument form of substr:
> >       `(let ((s ,str))
> >          (substring s ,from (string-length s)))
> >       ; three argument form of substr:
> >       `(substring ,str ,from (+ ,from ,@rest))))
>
> Scheme48 doesn't have `define-macro'-style macros (which are a bad idea
> anyway, as they are inherently unhygienic); you'd either have to use
> syntax-rules, or use explicit-renaming macros[0]. For the above example,
> I syntax-rules suffices:
>
> (define-syntax substr
>   (syntax-rules ()
>     ((substr str from)
>      (let ((s str))
>        (substring s from (string-length s))))
>     ((substr str from count)
>      (substring str from (+ from count)))))

I was hoping that there would be a simple way to define defmacro using
define-syntax and syntax-rules, but I can't find one.
(There is something which lookd promising in SLIB, but I couldn't
get it to work).

> > (3) scheme48 won't accept ++ as a symbol name for some reason:
>
> ++ is not a valid identifier according to R5RS (from the section
> "Lexical structure"):

OK, I have replaced ++ by concat, and also fixed the calls to "-"
which have more than two arguments (I know that (- z1 z2 ...)
is only "optional" in R5RS, but it can't be *that* hard to implement... :-))

> > ALL2.scm is 6.7MB of scheme source.
>
> I think your heap size is too small; try starting scheme48 with a larger
> heap size, e.g.:
>
> % scheme48 -h 30000000

I recompiled scheme48 with the BIBOP garbage collector, so that it will
grow the heap as needed, but it still chokes on my program:

% scheme48 -h 0
Welcome to Scheme 48 1.8 (made by martin on Tue Jul 14 23:24:14 BST 2009)
Copyright (c) 1993-2008 by Richard Kelsey and Jonathan Rees.
Please report bugs to [email protected].
Get more information at http://www.s48.org/.
Type ,? (comma question-mark) for help.
> (load "ALL.scm")
ALL.scm

Error: VM limit exceeded: segment too large
       309153
       (&error)
1> 

I get the same error with scheme48 -h 30000000,
or, for that matter, -h 300000000.



-- 
			Martin

[email protected] http://www.cse.dmu.ac.uk/~mward/ Erdos number: 4
G.K.Chesterton web site: http://www.cse.dmu.ac.uk/~mward/gkc/