Portability and Code walkers

["Scott E. Fahlman" <Fahlman@C.CS.CMU.EDU>]

We might or might not be able to agree to set up an absolute restriction
against macros expanding into non-standard special forms.  We could
require everyone to provide legitimate macro-expansions that are
equivalent to any non-standard special forms that the system really
uses, but whether this is useful depends on what you are using the code
walker for.  You don't want to optimize or modify these equivalent forms
and then have the system bypass the whole thing.

I think that most practical solution is to provide a good extension
language for your code-walker and then add templates for any unusual
special forms present in a given system.  The resulting system is not
100% portable, but the effort required to move it to a new system is
neglegible.

-- Scott