Re: Scheme mistakes (was Re: nil)

[Shriram Krishnamurthi <address@hidden>]

Alan Bawden wrote:

>    Date: Thu, 14 Aug 2003 15:01:49 -0500
>    From: Matt Hellige <matt@immute.net>
>    Mail-Followup-To: ll1-discuss@ai.mit.edu
> 
>    [Alan Bawden <Alan@lcs.mit.edu>]
>    > 
>    > Consider evaluating:
>    > 
>    >   (throw (f x) 42)
>    > 
>    > Since you know that the expression `(f)' must yield a continuation, the
>    > old continuation can be discarded (and perhaps reclaimed by the garbage
>    > collector) -before- you call the function `f'.  If continuations just look
>    > like procedures, then the programmer would have written:
>    > 
>    >   ((f x) 42)
>    > 
>    > is which case you don't know that the old continuation is going to be
>    > discarded until -after- the call to `f' returns a continuation.
> 
>    Is this really true? What if `f' causes an error? Mightn't we need the
>    old continuation to handle it correctly?
> 
> In pure R5RS Scheme I see no reason that old continuation can't be
> discarded.

But also, in pure R5RS Scheme I see no reason to program.

Shriram