Re: Four problems with Scheme 48 1.8

Martin Ward <[email protected]> writes:

> (1) Compiling with gcc version 4.4.0 gives an error on "make test":
>
> FAILURES:
> Test case *3 [misc-big-tests] FAILED:
>>From expression (* 47123 46039) EXPECTED value 2169495797 of 2169495797
> INSTEAD got -2125471499
>
> '(#{Check-failure #{Test-case *3} (actual (* 47123 46039) -2125471499) 
> (expected 2169495797 2169495797) #{Procedure 983 (equal? in 
> scheme-level-1)}})
>
> Compiling with gcc 4.0.1 seems to work OK.
>
I'll leave that one to more knowledgeable people than me.

>
> (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)))))

> (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"):

<identifier> --> <initial> <subsequent>*
     | <peculiar identifier>
<initial> --> <letter> | <special initial>
<letter> --> a | b | c | ... | z

<special initial> --> ! | $ | % | & | * | / | : | < | =
     | > | ? | ^ | _ | ~
<peculiar identifier> --> + | - | ...

So while `+' is a valid identifier, identifiers can not start with `+'
in general.

> scheme48
> Welcome to Scheme 48 1.8 (made by martin on Mon Jul 13 10:50:38 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 "ALL2.scm")
> ALL2.scm
> Condition: (&interrupt post-major-gc)
> 1> 
> Condition: (&interrupt post-major-gc)
> 2> 
>
>
> 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

HTH, Rotty
-- 
Andreas Rottmann -- <http://rotty.yi.org/>