Dear CIAO Users

I have been playing about with multithreading in CIAO Prolog and came across what I believe to be a strange side-effect of debugging on a simple piece of code.

If I load the following piece of code

:- use_module(library(dynamic)). :- use_module(library(concurrency)). :- concurrent p/1. :- concurrent q/1.

try:- eng_call(test,create,create).

test:- retract_fact(p(X)), asserta(q(X)).

And type

?- try.

I then am able to assert p(Something) and that gets re-written as q(Something):

?- asserta_fact(p(a)).

yes ?- retract_fact_nb(q(A)).

A = a ?

However, if I try to debug the code, then it won't work! Check it out:

?- try. 1 1 Call: user:try ? 2 2 Call: concurrency:eng_call($:(user:test),create,create) ? 2 2 Exit: concurrency:eng_call($:(user:test),create,create) ? 1 1 Exit: user:try ?

yes {trace} ?- asserta_fact(p(a)).

yes {trace} ?- retract_fact_nb(q(A)).

no

What is going on here? Am I missing something?

Thanks for any help!