Requested changes to R4RS

[Jonathan Rees <jar@zohar.ai.mit.edu>]

[Cc: Scheme-Standard deleted]

   Date: Thu, 25 May 89 02:19:56 -0700
   From: "Jonathan S. Shapiro" <shap@polya.stanford.edu>

   I think the peek-char debate centered around what peek-char's behavior
   was in the face of rubout handlers, which evolved from the discussions
   about char-ready?.  The problem is that if we can't define the
   semantics for char-ready?, a good argument can be made that for the
   same reasons we can't define the semantics of peek-char.  If it was
   there to be peeked at, and we can define what that means, then we can
   surely define what char-ready? means.

We need some suitable primitive to permit the construction of portable
readers.  Right now there is now way a user can write READ or anything
similar because there is no way to find out when you've encountered
the end of a symbol or number without gobbling the character that
delimits then symbol or number.  I don't care what the primitive is.
It doesn't have to be PEEK-CHAR, but we've got to have it.  Don't
just argue against PEEK-CHAR; explain how we can solve the READ problem.

I think CHAR-READY? is a much less interesting and important question.
If it is made possible by progress on the READ problem, fine, but
that's a secondary issue.

What does X3J13 Common Lisp say about the interaction of PEEK-CHAR and
input editing?