Re: [eclipse-clp-users] Suspend till tentative value change

On 04/02/16 02:01, Edgaonkar, Shrirang wrote:
> Dear clp users,
>
>   I wish to suspend a predicate till a change in tentative value occurs to one
> of its variables. I get the following error "out of range in suspend(cast(_612,
> _613), 1, _613 -> tent_chg, 'SUSP-5-susp') in module eclipse"
>
> for the following script
>
> :- lib(tentative).
> solve(R):-
> cast(Number,String),
> tent_set(String, 1).
>
>
> cast(Number,String):-
>    (var(String)->
>    suspend(cast(Number,String),
>     1, String->tent_chg, Susp2);writeln(instantiated),true).
>
> Whenever tentative value of String changes it should invoke cast(Number,String)
> is the intention.

Two issues here:

1. write  String->tentative:tent_chg  instead of just  String->tent_chg
    (this is wrong in the manual, sorry)

2. you can only suspend on the tent_chg condition when the variable
    already has a tentative value.  So you have to call tent_set/2 before.

And a third recommendation: don't use 1 as the suspension priority
(it is the highest priority, and reserved for debugging purposes).
Use 0 for default, or 2 and higher.


Cheers,
Joachim