[det]trap(+Formal)error(Formal, Context) exceptions that
unify. The tracer is started when a matching exception is raised. This
predicate enables debug mode using debug/0
to get more context about the exception. Even with debug mode disabled
exceptions are still trapped and thus one may call nodebug/0
to run in normal mode after installing a trap. Exceptions are trapped in
any thread. Debug mode is only enabled in the calling thread. To enable
debug mode in all threads use tdebug/0.
Calling debugging/0 lists the enabled traps. The predicate notrap/1 removes matching (unifying) traps.
In many cases debugging an exception that is caught is as simple as below (assuming run/0 starts your program).
?- trap(_). ?- run.
The multifile hook trap_alias/2 allow for defining short hands for commonly used traps. Currently this defines
- det
- Trap determinism exceptions raised as a result of the det/1 directive.
=>- Trap rule existence error exceptions.