Subject: Re: Dylan and Lisp
From: Erik Naggum <>
Date: 1999/11/09
Newsgroups: comp.lang.lisp
Message-ID: <>

* Jochen Schneider <>
| I got a related question.  Does CL have "primitive types"?

  yes, but we name them accurately "system classes".  a _type_ is a set of
  values of a given class.  some languages don't have any means to express
  this, so conflate "type" with "class".  some languages don't have type
  hierarchies and think "primitive type" is a good idea to make different
  from all other types.  this is an issue of forcing the user to be acutely
  aware of implementational considerations on the hardware, so the types
  should be more accurately be called "hardware types" and "software types"
  in such languages.

| I mean, can or can't you write a method for, e.g., numbers that get
| dynamically dispatched?

  yes, NUMBER is a system class.  so are its two disjoint subtypes REAL and
  COMPLEX, the two disjoint subtypes RATIONAL and FLOAT of REAL, and the
  two disjoint subtypes INTEGER and RATIO of RATIONAL, but the subtypes
  system classes.  you can still dynamically dispatch on them in most CLOS
  implementations, however, because they form implementation classes.

| What's the deal with the typecase macro?

  it is to TYPEP what EQL is to CASE.  (I don't think this answered your
  question, but it is not a very answerable question -- it seems to say,
  because of the preceding tone, that you disapprove of it because it isn't
  OO, which is a silly reason.  I can't make you approve of something you
  don't yet understand, and won't waste my time to help you understand when
  approval precedes understanding.  back up a bit and desire to understand
  before you want to approve or disapprove, and this might change.)

  Attention Microsoft Shoppers!  MS Monopoly Money 6.0 are now worthless.