Re: Why <empty-list> and <pair>? or More heresy...

[alms@cambridge.apple.com (Andrew LM Shalit)]

At  1:36 PM 12/1/92 +0100, Jonathan Bachrach wrote:
> All this talk of the lack of a need for <true> and <false> classes has
> made me wonder why it is necessary to have an <empty-list> class.  Why
> can't people just use `(singleton '())'?  Given that, why even have a
> <pair> class?  Programs can distinguish between a <pair> instance and
> an <empty-list> instance using the same `(singleton '()).  This change
> would definitely simplify the class structure.  Granted, in some cases
> programmers might need to employ two methods to flag list arguments
> that must be non-empty, such as for `(setter car)', but in most cases
> they need to handle '() specially anyway and would be writing a
> separate method for it.

I think it would be perfectly reasonable to do away with <empty-list>,
and use (singleton '()) instead.  Note that () would be an instance
of <list> but not of <pair>.