incremental definitions

[Gerhard Eckel <V4110DAA%AWIUNI11.BITNET@mitvma.mit.edu>]

In Digest #123 William Clinger <uoregon!will@beaver.cs.washington.edu> writes:

> Neither EVAL nor THE-ENVIRONMENT are part of Scheme, so the fact that XScheme
> happens to define procedures with those names that happen not to work the way
> someone expects has no bearing on whether it is a real Scheme system.

> Most people think it is better to think of incremental definitions as part
> of a programming environment instead of a language, since they are primarily
> used for debugging.  The programming environment obviously differs from one
> implementation to another, so code that depends on the programming environment
> is not portable.

   Is it  possible to  design an  object-oriented layer  which implements the
concepts of classes, inheritance and polymorphism in pure Scheme?   Something
like Scoops seems to be impossible  to build without functions like EVAL  and
THE-ENVIRONMENT.  In the case  of Scoops incremental definitons are  used for
much more than  debugging.  What  could I do  if I would  like to make Scoops
portable?  Am I completely missing the point?

Gerhard Eckel, v4110daa@awiuni11.bitnet