Re: why does this not work

> Date: Tue, 25 Mar 2014 15:40:53 +0100
> From: [email protected]
> To: [email protected]
> Subject: Re: [SWIPL] why does this not work
> 
> On Tue, Mar 25, 2014 at 14:32:03 +0000, Roelof Wobben wrote:
> > % Displays the output of siblings(X,Y) and takes care that 
> > % there are no duplicates.
> > display_siblings(Person) :-
> >       findall(Person-Y, (siblings(Person,Y),Person @< Y), Sibs),
> >        display_the_siblings(Sibs).
> > [...]
> > But when I do display_siblings(kimberly) I see a message Er zijn geen zussen/broers bekend
> > That's wrong Denise is a sibling of Kimberly.
> 
> ?- Person = kimberly, findall(Person-Y, (siblings(Person,Y),Person @< Y), Sibs).
> Person = kimberly,
> Sibs = [].
> 

If I change it to what you said :

% Displays the output of siblings(X,Y) and takes care that 
% there are no duplicates.
display_siblings(Person) :-
      findall(Person-Y, (siblings(Person,Y)), Sibs),
      display_the_siblings(Sibs).

Then I see these error messages:

ERROR: /home/roelof/prolog/gene:28:0: Syntax error: Operator expected
ERROR: /home/roelof/prolog/gene:34:0: Syntax error: Operator expected

Roelof
 		 	   		  
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