Re: [Gcl-devel] More on proclaim error

[Paul F. Dietz]

Camm Maguire wrote:
> Greetings!  The issue regards type specifiers of the form
>
> (satisfies foop)
>
> where foop is a user defined predicate.  I'm assuming typep and
> subtypep can always return nil for such types?  I'm wondering in
> particular if any class hierarchy or other known structure could allow
> a non-nil return in certain circumstances.

SUBTYPEP is allowed to return NIL, NIL, but TYPEP has to do the
right thing.  For example:

  (typep x '(satisfies foop)) ==> (funcall (symbol-function foop) x)

Note the page for TYPEP:

  A type-specifier of the form (satisfies fn) is handled by applying
  the function fn to object.

        Paul