[Openmcl-devel] deftype bug?

[Nikodemus Siivola]

On 18 March 2010 16:11, Paul Krueger <plkrueger at comcast.net> wrote:

> also include a "satisfies" type. I'm curious if anyone knows why the
> serial semantics that were so clearly defined in CLtL2 were not
> adopted for the standard; oversight or choice?

At a guess, because it would mean that set-theoretical notion of types
goes out of the window. Consider the type

  (or (and x y) (and z y))

this is -- in ANSI Common Lisp -- equivalent to both types

  (and (or x z) y)
  (and y (or x z))

but under CLtL2 is certainly not equivalent to the last one. Consider
further what should should

  (subtypep '(and (or x z) y) '(and y (or x z)))

return? In ANSI CL the answer is a clear and resounding T, T. CLtL2 I
have no clue about.

Cheers,

 -- Nikodemus