Re: URGENT RESPONSE REQUESTED!!!!!

["J. A. Durieux" <xerox@cs.vu.nl>]

One common problem I run into when #F == () is to distinguish
between failure and an empty successful response,
e.g. of a matcher or unifyer.  [Plug for failure semantics ... :-)]

My common way around has been to build the response list on e.g. #T
instead of #F.  (Other solutions, like an extra cons around the
answer, are much uglier.)
But alas, in Scheme all standard functions (like assoc, member, etc.)
refuse to deal with such a "non-proper" (sic!) list.

So, *if* it has to remain acceptable that lists may end in #F,
one should allow them to end in other values as well (just #T
would do).  Of course, that is no acceptable solution,
given the state of affairs, so:

    I am strongly in favour of distinguishing #F and ().



Sorry for my clumsy English,
					J. A. "Biep" Durieux