Re: [eclipse-clp-users] Question about suspend

Ulrich Scholz wrote:
> Hi,
> 
> I'd like to write a demon that wakes when an ic variable gets constrained.
> Also, it should wake if the ic variable is made equal to another ic variable
> with same bounds.  
> 
> Somehow, I seem to set up the condition list it in a wrong way.  Consider
> the three examples given below.  Only t2 weakes the demon.  How can I set up
> a demon that wakes in case t3?
> 
> Thanks,
> 
> Ulrich
> 
> 
> I'm using ECLiPSe Version 6.0 #154 (i386_linux)
> 
> ----
> :- lib(ic).
> 
> :- demon d/0.
> 
> d :-
>     writeln("suspension woken").
> 
> t1 :- 
>     suspend(d, 0, [X->bound], _S),
> 
>     X = Y.
>     
> t2 :- 
>     X :: [0..100],
>     
>     suspend(d, 0, [X->bound, X->constrained], _S),
> 
>     Y :: [0..50],
>     
>     X = Y.
>     
> t3 :- 
>     X :: [0..100],
>     
>     suspend(d, 0, [X->bound, X->constrained], _S),
> 
>     Y :: [0..100],
>     
>     X = Y.

Unification of X with an "unrelated" Y will not cause waking.

You have to include Y in the trigger condition like this:

t4 :-
    X :: [0..100],

    suspend(d, 0, [[X,Y]->bound], _S),

    Y :: [0..100],

    X = Y.

See http://eclipseclp.org/doc/userman/umsroot111.html#toc130


-- Joachim