----- Original Message -----
From: "Dan Muresan" <dan-r6rs_at_omnigia.com>
To: <czhu_at_cs.utah.edu>
Cc: "Jason Orendorff" <jason.orendorff_at_gmail.com>; <r6rs-discuss_at_lists.r6rs.org>
Sent: Wednesday, September 20, 2006 5:17 PM
Subject: Re: [r6rs-discuss] "Unspecified"
>> which I do use in my program. PLT doesn't provide a direct way to get the
>> "undefined" value, so I'm glad to see the "unspecified" value given
>
> I'm not sure what you mean by "direct way", but
>
> (define x (if #f #f))
I'm talking about the *undefined* value of PLT Scheme. "(if #f #f)" returns the *void* value in PLT.
And "(values)" pass 0 value(s) to the current continuation (according to R5RS). Ther are all different from each other.
> works. Interestingly, (define x (values)) does not work, so PLT
> distinguishes between 0 values and undefined.
>
>
> Best,
> Dan Muresan
> http://alumnus.caltech.edu/~muresan
>
Chongkai
Received on Wed Sep 20 2006 - 19:42:47 UTC