Re: proper tail recusion for `or'

[John Clements <clements@cs.rice.edu>]

>Please, correct me if I am wrong.  By using the stepper, it seems that
>DrScheme do not handle tail recursion properly for `or'.  Is this a bug?
>
>Here is an example:
>
>   (define (list-or l)
>     (if (null? l)
>         #t
>         (or (car l) (list-or (cdr l)))))
>
>   (list-or (list #f #f #f #f #f #f #t))
>
>Thank you.
>MM

If I understand you correctly, you're surprised by the fact that, 
say, (or #f M) reduces to (or M), rather than directly to M.  This is 
because the beginner and intermediate languages require that all 
arguments to or be booleans.  If M was tail w.r.t the expression (or 
#f M), this check would not be possible.

Does this answer your question?

john