Re: Fwd: Re: behavior of CASE with strings PART 2

Hi Damien

Your macro might work on some implementations, but is not R5RS compliant.
Ellipses ("...") must always be the last item of a list or vector before
the closing ")", (unless the last item is a pair).

If you want a general solution, I think you should go for this:

(define-syntax case*
        (syntax-rules (else)
                ((case* (key ...)
                        clauses ...)
                 (let ((atom-key (key ...)))
                        (case* atom-key clauses ...)))
                ((case* key
                        (else result1 result2 ...))
                 (begin result1 result2 ...))
                ((case* key
                        ((atoms ...) result1 result2 ...))
                 (if (member key '(atoms ...))
                        (begin result1 result2 ...)))
                ((case* key
                        ((atoms ...) result1 result2 ...) clause clauses
...)
                 (if (member key '(atoms ...))
                        (begin result1 result2 ...)
                        (case* key clause clauses ...)))))


Best regards


Bent

2017-01-20 16:24 GMT+01:00 <[email protected]>:

> Hi Marc,
>
> Nice to see you here ;-)
>
> > Note that you can use symbols with the case construct.  In other words,
> these two expressions are equivalent if str is a string:
> >
> >  (cond ((string=? str "foo") 111)
> >        ((string=? str "bar") 222)
> >        (else                 333))
> >
> > and
> >
> >  (case (string->symbol str)
> >    ((foo) 111)
> >    ((bar) 222)
> >    (else  333))
> Agree with a minor warning. Although its probably not a problem in that
> particular situation but in my own programs I try to limit the use of
> symbols
> as much as possible as these objects are never collected.
>
> --
> Manuel
>