From: VIQAR ABBASI
Subject: The function READ
Date: Sun, 16 Oct 1994 21:40:57 +0000
Message-ID: <CxsC89.FFI@ariel.cs.yorku.ca>

I would like to know if there's a way to access the contents of the function 
READ before it is completely evaluated.  So, if the input is not in the form
of a lisp expression, it may be considered a special case.

For example:

	(cond ((equal (read) "exit") (return ())
              (t eval(read))

* This is not exactly what my task calls for, but I think it illustrates the
concern.... Help?

Viqar Abbasi

From: Barry Margolin
Subject: Re: The function READ
Date: Mon, 17 Oct 1994 02:16:50 +0000
Message-ID: <37smqi$a7@tools.near.net>

In article <··········@ariel.cs.yorku.ca> ········@ariel.cs.yorku.ca (VIQAR ABBASI) writes:
>For example:
>
>	(cond ((equal (read) "exit") (return ())
>              (t eval(read))

You could put the result of the (read) in a variable, and test it before
evaluating it:

(let ((input (read)))
  (if (eq input 'exit) (return '())
      (eval input)))

If the special sequence isn't valid Lisp syntax, you could use READ-LINE
and then READ-FROM-STRING.  For instance, if you wanted to use a line
consisting of a single "." as the exit trigger:

(let ((input (read-line)))
  (if (equal input ".") (return '())
      (eval (read-from-string input))))
-- 

Barry Margolin
BBN Internet Services Corp.
······@near.net