From: Bill Clementson
Subject: What is the origin of s-expression
Date: Fri, 06 Sep 2002 21:43:12 +0000
Message-ID: <wkznuuzt9j.fsf@attbi.com>

I know that the term "s-expression" stands for "symbolic expression" and
I know what its meaning is in the context of Lisp; however, I have been
using the term for some time without any awareness of its origin or
pre-Lisp meaning. This started to bug me & I recently decided to see if 
I could find out where the term might originate from. 

Google didn't provide any sites with definitions of the origin of
the term. Neither did CLHS, CLtL2, nor the dozen Lisp & AI books that I
checked. I searched through a number of the Lisp papers that I've down-
loaded from the web and, eventually, I got to John McCarthy's original 
paper on Lisp. In it, he discusses 3 types of expressions:

1. Symbolic-expression or S-expression or s-exp
2. Meta-expression or M-expression 
3. Lambda-expression 

However, it is not clear in the paper whether he invented the terms or
whether they are Mathematics terms or whether they originate from some
other domain. 

So, before I waste any more time on this, can anyone enlighten me on
what the original source of the term "symbolic expression" is? 

--
Bill Clementson

From: Jim White
Subject: Re: What is the origin of s-expression
Date: Sat, 07 Sep 2002 04:45:16 +0000
Message-ID: <3D798458.9010003@pagesmiths.com>

Bill Clementson wrote:
>... 
> So, before I waste any more time on this, can anyone enlighten me on
> what the original source of the term "symbolic expression" is? 

McCarthy invented/introduced the term "symbolic expression" as we 
understand it in computing.  The earlier work was mathematical and used 
different terminology.  Prior relevant use of the term "symbol" was by 
Turing, which he used with the tape machine metaphor.  With LISP, 
McCarthy took the computing symbol concept but applied it to expressions 
in the Lambda calculus (Church et al).

jim