Re: pldoc: how to specify predicates with arguments unbound.

On Sep 17, 2014, at 12:51, Richard A. O'Keefe <[email protected]> wrote:

> 
> On 16/09/2014, at 5:57 PM, Kuniaki Mukai wrote:
> 
>> 
>> Hi, 
>> 
>> Using pldoc, how do we specify a predicate such as follows:
>> 
>> 	foo(X, Y) :-  (random(3) =:= 2, X==Y;  true).
> 
> This is logically equivalent to foo(_, _).
> Did you mean
> 
> 	foo(X, Y) :- ( random(3) =:= 2 -> X == Y ; true ).
>                                       ^^

What I intended to write is the following:

foo(X, Y) :-  (random(3) =:= 2, X=Y;  true), !.

?- foo(X, Y), X==Y.
%@ X = Y .
?- foo(X, Y), X==Y.
%@ false.
?- foo(X, Y), X==Y.
%@ X = Y .

I wrote a unifier on rational trees on Edinburgh Prolog in ancient time
writing clauses  for unbound arguments to test whether two variables are
already unified or not.  I am afraid that such kind of prolog programming 
is no more recommended nowadays from view of mode declaration.

Thank you for pointing my careless typo.

Kuniaki Mukai

> 
> 
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