Subject: Re: Macros in Common Lisp, Scheme, and other languages
From: Erik Naggum <>
Date: 07 Sep 2002 20:49:54 +0000
Newsgroups: comp.lang.lisp,comp.lang.scheme,comp.lang.functional
Message-ID: <>

* Paul F. Dietz
| This would work, but I see some problems.

  All of them implementation restrictions.  If we wish to make macros better by
  augmenting them with environment information, that would require some work
  to improve existing compilers.  If not even the work necessary to remove the
  implementation restrictions that you point out is sufficiently motivated by
  the improvements that we could clearly obtain at the far side of availability
  of better compilers, what would motivate the universal implementation of
  environment information for macros?  Do you see the effort required to add
  environment information as significantly less than that required to fix the
  problems you have encountered in existing compilers?  If so, on what have
  you based this assessment?

  I think the current language is strong enough to do what we want to do with
  Common Lisp, and that the macro system does not need improvement for any
  /semantic/ reasons.  However, there is a difference in /convenience/ that might
  provide programmers with an impetus to change their ways when optimizing
  their code if they had macros that could significantly simplify the task for
  the compiler, and they could observe improvements in the compiled code.

  However, I can hardly imagine such improvements to be disconnected, so one
  who wanted to make type-sensitive improvements to Common Lisp code would
  want a compiler that could do it with the current language.

  As to the exponential growth, I do not understand the purpose of pointing
  out hard problems before we even know where to go with simpler ones.  What
  matters is the conditions under which the solutions will scale well and under
  which it would not.  I would not be very surprised to see n-ary functions
  fail to be optimizable with this scheme, but that should not deter us from
  making improvements that would mainly improve less complex functions.

Erik Naggum, Oslo, Norway

Act from reason, and failure makes you rethink and study harder.
Act from faith, and failure makes you blame someone and push harder.