=head1 TITLE

All perl generated errors should have a unique identifier

=head1 VERSION

  Maintainer: Chaim Frenkel <chaimf@pobox.com>
  Date: 9 Aug 2000
  Last Modified: 19 Sep 2000
  Mailing List: perl6-language@perl.org
  Number: 85
  Version: 2
  Status: Developing

=head1 ABSTRACT

All perl generated errors should have a unique identity. So that
changes in the text should not cause breakage in code.

=head1 DESCRIPTION

Currently many programs handle error returns by examining the text of
the error returned in $@. This makes changes in the text of the error
message, an issue for the backwards compatibility police.

In addition error messages can be localized without effecting a
working script.

=head1 CHANGES

=item *

Removed any mention of language implementation as part of this RFC.
This is too dependent upon other changes in the language.

=head1 IMPLEMENTATION

Each unique identifier once assigned as part of a stable release
of perl will be guarenteed never to be changed, or if the error
text is removed, never to be reused.

This RFC currently makes no attempt to define the actual methodology
of how the unique ids are assigned or how they will be made available
at the language level.

However some discussion was sparked by the original RFC and is left
as a historical note.

=head1 Appendix

=head2 Unique number

Each error message will be assigned a unique number. The number
could be made accessible via the $@ in a numeric context.

This would be simple and direct. With no major hassles.

=head2 Unique String

Each error message will have a unique string assigned.

The unique string could be accessible as

	$@->id

An id string could have some structure associated to enable 
better handling. One suggestion was to follow the lead of VMS.

	facility:
		The program (or, in perl's case, the thing that errored)
	status:
		I=information, W=warning, E=error, S=Severe error
	message-code:
		A one word abbreviation for the text message 

	text message:
		A human readable string with more detail

	A sample error:

	%APPEND-I-CREATED, MEM.SUM;1 created

For perl the actual text would be in $@.

or rather than make the user break up the text string the values
could be supplied as

	$@->id		# The unique identifier for this error
	$@->facility	# regex, io, syscall
	$@->severity	# Fatal, Warning, Informationl, 

=head1 Aknowledgements

Bryan C. Warnock <bwarnock@gtemail.net>
Peter Scott <Peter@PSDT.com>
Uri Guttman <uri@sysarch.com>
Ariel Scolnicov <ariels@compugen.co.il>
Juanma Barranquero <lektu@uol.com.br>
"Paul L. Allen" <pla@softflare.net>
Brian Wheeler <bdwheele@wombat.educ.indiana.edu>

=head1 REFERENCES

IBM Messages and Codes

VMS (anyone have a reference)

SCCS