Subject: Re: Comments, was Re: Parentheses Hierarchy
From: Erik Naggum <>
Date: 1999/07/26
Newsgroups: comp.lang.lisp
Message-ID: <>

* Kent Pitman
| Your mechanism would force it to be the case that certain objects could
| never be notated in a program visible way because those objects would be
| removed if I tried to make them program-visible.

* Tom Breton
| Such objects already exist.  They are called comments.  I apologize for
| my tone, but after saying this in several ways already, I find myself a
| bit frustrated in explaining it.  Think of the comments as comments.

  consider a list (foo bar zot), where one of the elements is present in
  one interpretation of the list and absent in another.  what determines
  whether it be present or not?  in your design, the evaluator determines
  whether the element is present.  Kent objects to that.  I have suggested
  that you use two different READ functions, one which returns the list
  with that element, and one which doesn't, because it would be necessary
  to deal with the element in code, and so it would be necessary for the
  evaluator to be able to deal with that object, not just excise it.

  incidentally, you would need a comment object that is a bit more complex:
  it needs to know the column at which it starts, the number of semi's if
  you don't do that as part of the comment string, and whether it was a
  #|...|#-style or a ;-style comment.  an editor would need to know the
  exact location on the line of every form, not just comments, however, and
  it seems awfully naïve to believe that the only thing you'd need to get
  this right would be to retain comments in the flow of the other data.

  Tom, it's a bad idea.  it has been tried, and it was garbage collected.

  suppose we blasted all politicians into space.
  would the SETI project find even one of them?