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To: "Lyosha" <ai@solvo.ru>
Cc: <prolog@swi.psy.uva.nl>
Subject: Re: [SWIPL] Q
References: <200108160302.PAA62210@atlas.otago.ac.nz> <004b01c12658$e19c9f00$c901a8c0@MINERVA> <005701c126bb$6663c940$102cc9c3@elbrus>
From: Tom Breton <tob@world.std.com>
Date: 16 Aug 2001 12:09:47 -0400
In-Reply-To: "Lyosha"'s message of "Thu, 16 Aug 2001 18:24:45 -0700"
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"Lyosha" <ai@solvo.ru> writes:

> If [] is not a list then I would expect is_list([]) to fail. However it
> succeeds, which
> of course we can treat as an exception. :)


is_list(+Term)
    Succeeds  if Term is  bound to the  empty list ([])  or a term  with
    functor `.' and arity 2.


It's the same behavior as in Lisp, where it's a little easier to
understand.  The empty list ([] or nil) is the list terminator alone.


-- 
Tom Breton, http://world.std.com/~tob

