1.54.2 Send methods

error ->display: unchecked ...

Present the error to the user or programmer. This method may be redefined to present the error in a different way. The default implementation performs the following actions:

• if error<-feedback equals report Invoke object->report using error<-kind, error<-format and the arguments passed. This message is sent to the object that generated the error using object->error.
• if error<-feedback equals print Use’@pce error->format’to print the message. If error<-kind is error, start the PCE tracer.

error ->initialise: name=name, format=string, kind=[{status,inform,warning,error,fatal,ignored}], feedback=[{report,throw,print,backtrace}]

Create an error from its error<-id, error<-format, error<-kind and error<-feedback. The default kind is warning and the default feedback is report. The error object is locked against the garbage collector and a mapping from its error<-id is added to the @errors database.

The following provides a (schematic example).

:- new(_, error(key_clash,
                                '%N: Key %s is already in use')).

:- pce_begin_class(database, hash_table).

add(DB, Record:record) :->
        "Add record to the database"::
        get(Record, key, Key),
        (   get(DB, member, Key, _)
        ->  send(DB, error, key_clash, Key),
                fail
        ;   send(DB, append, Key, Record)
        ).

:- pce_end_class.

See also object->report.