From fadushin@blackcat.cat.syr.edu  Fri May 21 15:30:21 1999
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Date: Fri, 21 May 1999 09:31:55 -0400 (EDT)
From: Fred Dushin <fadushin@blackcat.cat.syr.edu>
Reply-To: fadushin@blackcat.cat.syr.edu
To: Amir Wolf <amirwolf@netvision.net.il>
cc: "'prolog@swi.psy.uva.nl'" <prolog@swi.psy.uva.nl>
Subject: Re: the meaning of ";"
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On Thu, 20 May 1999, Amir Wolf wrote:

> What is the meaning  of  " ; " in prolog 

'Or', last time I used it.  

> and what is the meaning of  " () " ?

Do you mean '()' or '(t_1, ..., t_n)'?

In general, () is used by the prolog parser to group terms
using infix operators (',', ';', etc.)  Jan may have
a better answer to this.

An interesting observation:  ',' is a *binary* functor,
despite its occurrence in terms like '(t_1, ..., t_n)'.
Internally, such a term has the following represenatation:

	','( t_1, ','( t_1, ..., ','( t_{n-1}, t_n )...))

Maybe Jab can clarify for other cases, like ';' or user-defined
operators.

-Fred

--
Fred Dushin                      mailto:fadushin@syr.edu
PGP public key available at      http://blackcat.cat.syr.edu/~fadushin/pgp

