[r6rs-discuss] [Formal] Expand the set of self-evaluating datums

[Pascal Costanza]

On 22 Jan 2007, at 19:37, John Cowan wrote:

> Peter Gavin scripsit:
>
>> I don't think the empty list should be self-evaluating.  No other  
>> list
>> in scheme is self-evaluating, so why should the empty one be?
>
> Because it can be neither syntax (which must have a keyword) nor a  
> function call
> (which must have at least one form).  Making () self-evaluating  
> also represents
> a return to Lisp tradition; it would be interesting to know why it  
> was made
> *not* self-evaluating in RRRS.

My guess is this was because of the wish to separate the different  
meanings of NIL in traditional Lisp dialects, where NIL is at the  
same time a symbol, the empty list and the boolean value false.


Pascal

-- 
Pascal Costanza, mailto:pc at p-cos.net, http://p-cos.net
Vrije Universiteit Brussel, Programming Technology Lab
Pleinlaan 2, B-1050 Brussel, Belgium