wait-for Predicates

Predicate wait-for/1 can be used by the current thread to wait for some event to occur. In previous releases of COCA, when a message was expected from a certain object, we needed an active rule to wait for it. This new construct can make it simpler and clearer. For example, when a message is sent to an object and an answer is expected from it, we simply specify the following.

A second argument can be added to wait-for which specifies the timeout period before wait-for/2 can be failed. Any nonnegative number is valid or the symbol ``$\infty$'' can be used to denote infinity. If it is an unbound variable, when the predicate succeeds this variable is bound to the length of time from when the wait-for was executed until the event occurred.