
error(++EventId, ?Culprit, +Module)

   An error EventId is raised with Culprit and context module Module, and the corresponding error handler is executed

Arguments
   EventId             Atom, integer or structure with functor default/1.
   Culprit             Prolog term.
   Module              Atom.

Type
   Event Handling

Description
   The event or error EventId with Culprit as its culprit goal is raised.
   EventId is either an integer error number, or an atomic event name.
   The error handler which is associated with EventId is invoked,
   with its first argument set to EventId, its second argument to Culprit,
   its third argument to Module, and its fourth argument to the context module
   in which error/3 is invoked. If the handler has less than four arguments,
   the extra information is lost.

   This simulates an occurrence of the error EventId inside a call
   to Culprit in Module.  The valid error numbers are those returned by
   current_error/1.  Event names can be any atom as long as an event handler
   has been defined for them.

   If EventId is a structure with functor default/1, the structure argument
   is taken as the error number and the default handler is executed, even
   if the error handler has been redefined using set_event_handler/2.
   This is useful for writing user error handlers.

   If the event handler succeeds, possibly binding some variables
   inside Culprit, then error/3 succeeds as well. If the handler fails
   or calls exit_block/1, then so does error/3.

   Not that when the error handler ignores the module (ie.  has arity less
   than three), then error/2 and error/3 are equivalent.



Modules
   This predicate is sensitive to its module context (tool predicate, see @/2).

Fail Conditions
   Fails if the handler fails

Resatisfiable
   Resatisfiable if the handler is resatisfiable

Exceptions
     4 --- EventId is not instantiated.
     5 --- EventId is not an error specification.
     6 --- EventId is a number but not a valid error number.
    32 --- No handler is associated to EventId

Examples
   
Success:

    ?- error(68, length(X, Y), lists).
    calling an undefined procedure eclipse:length(X, Y) in module lists

   % writing an alternative error handler for undefined predicates:
    ?- arg(1,2).           % we want to change this
    calling an undefined procedure arg(1, 2) in module eclipse

    ?- [user].             % compile the new handler

     undef_handler(_, Goal, _Context, Module) :-
            functor(Goal, Name, BadArity),
            (
                current_predicate(Name/Arity)@Module
            ;
                current_built_in(Name/Arity)@Module
            ),
            !,
            printf("%w does not exist, but there is %w\n",
                               [Name/BadArity, Name/Arity]),
            fail.
     undef_handler(Err, Goal, Context, Module) :-
            error(default(Err), Goal, Context, Module).
     user compiled 592 bytes in 0.02 seconds
    yes.

    ?- set_event_handler(68, undef_handler/4).
    yes.

    ?- arg(1,2).            % check if it works
    arg / 2 does not exist, but there is arg / 3

    no.

Error:
      error(N,dummy(1),eclipse).    (Error 4).
      error(5.0,dummy(1),eclipse).  (Error 5).
      error(-2,dummy(1),eclipse).   (Error 6).
      error(95,dummy(1),eclipse).   (Error 6).





See Also
   error / 2, event / 1, current_error / 1, error_id / 2, get_event_handler / 3, reset_event_handler / 1, reset_error_handlers / 0, set_event_handler / 2
