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|library(prolog_debug): User level debugging tools|
This library provides tools to control the Prolog debuggers. Traditionally this code was built-in. Because these tools are only required in (interactive) debugging sessions they have been moved into the library.
informational, with one of the following terms, where Spec is of the form M:Head.
forall(debugging_hook, true)and that may be used to extend the information printed from other debugging libraries.
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.