From: Erik Naggum <>
Date: 05 Sep 2002 10:32:01 +0000
Newsgroups: comp.lang.lisp
Message-ID: <>

* Tim Bradshaw
| But don't I need to know if there *was* any whitespace?

  No.  Why do you think you need it?

| I think that (peek-char t) fails to distinguish between the first and second
| of these cases.

  We have the following situation.  After a token has been read, you are
  either looking at a terminating macro character or a non-constituent
  character such as whitespace.  This is an invariant.  Before you read a
  token, you skip any whitespace.  This is an invariant.  So you read the
  token.  If that token is the consing dot, you read the next token and should
  now look at the closing paren.  You interpret and add the last read token to
  your list in the appropriate manner and continue or return as appropriate.

| But I am now quite confused about the whole thing.

  I completely fail to understand what can be confusing here.  The reader
  algorithm is described in detail in the standard and in CLtL2.  I think you
  may have confused yourself by trying to see the consing dot after you have
  interpreted the tokens.

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.