[Martin Meyer]

Hello Thomas,

please check this; it might be a mistake otherwise please explain: Running the code

Code: Select all

class facts
    myMutex : mutex := mutex::create(false).
 
clauses
    run() :-
        %stdIO::write(toBoolean(myMutex:isSet())),
        myMutex:release().

throws an exception because a mutex that has not been entered cannot be released. However, if the commented-out line is enabled, no exception occurs and “true” is output.

Apparently, isSet/0 changes the state of the mutex. Yet the name suggests that the predicate is merely intended to query the state.

[Thomas Linder Puls]

Yes, you are right our implementation of isSet (which is used for many other things than mutex'es) doesn't work for a mutex, because it will actually acquire the mutex.

There is no way to test ownership of a mutex, so I think we will implement the predicate to raise an exception for mutexes.