                          Carp::Datum 0.1
     Copyright (c) 2002, Dave Hoover
     Copyright (c) 2000-2001, Christophe Dehaudt & Raphael Manfredi

------------------------------------------------------------------------
    This program is free software; you can redistribute it and/or modify
    it under the terms of the Artistic License, a copy of which can be
    found with perl.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    Artistic License for more details.
------------------------------------------------------------------------

========================================================================
This module is known to exercise a bug in perl 5.6.0.  Don't use that
version of perl: use 5.005_03, or try 5.6.1.

If ran under 5.6.0 nonetheless, the t/failmsg_on tests will be skipped.
========================================================================

       *** This is alpha software -- use at your own risks ***

Name           DSLI  Description                                  Info
-----------    ----  -------------------------------------------- -----
Carp::Datum    adpf  Debugging And Tracing Ultimate Module        CDE

========================================================================

This module is the Perl version of a C/C++ library, called DATUM, which
Christophe Dehaudt & Raphael Manfredi used in many programs since 1996.

Following is the preamble to the DATUM library, written by Raphael in 1998:

--- Begin Exerpt:

A bug in a software system may have multiple causes. It can be the result
of an oversight, a typo, a misunderstanding, a misuse, etc... Being able
to identify the presence of a bug, and then nail it down as quickly as
possible were the reasons of our deciding to create debugging foundations.

During the bug hunting phase, a developer needs to be able to trace
routine execution around the suspected bug spot, which is a moving target
usually. Flexibility of the tracing subsystem is therefore mandatory to
only be able to trace a specific area of the software.

Detecting bugs as early as possible is also recognized as the most
efficient route to quality, and it is certainly economically justified.
By following the Design by Contract principle, i.e. by inserting pre- and
post-conditions to specify the interfaces, one guards against improper
implementations and also formally documents the original intent of the
designer. That is also an invaluable aid during maintenance or evolution,
since it avoids improper use of existing interfaces that could otherwise
lead to havoc when left undetected.


    NOTE: It is a wise practice to develop and test a piece of
    software with all the assertions turned on (that includes pre- and
    post-conditions, but also any additional assertion checking within
    the code), and release it with only pre-conditions enabled. Indeed,
    software correctness is compromised when any pre-condition is
    violated.

--- End Exerpt.

Carp::Datum implements the following features:

* Programming by contract: pre-conditions, post-conditions, assertions.
* Flow control tracing: routine entry, arguments, returned values
* Dynamic (i.e. runtime) configuration via mini language to tailor
  debugging and/or tracing at the routine / file / package / type level.
* Ability to statically remove all assertions and flow control tracing
  hooks in modules making use of Carp::Datum.
* Cooperation with Log::Agent for tracing.

In order to do so, the following routines are provided:

	Assertions:   DREQUIRE, DENSURE, DASSERT
	Flow control: DFEATURE, DVAL, DARY, DVOID
	Tracing:      DTRACE

A sepcial precondition, VERIFY, is always kept (i.e. never stripped)
and can be used for checking important conditions, to write:

	VERIFY $pre_condition, "message";

where one would otherwise use a test like:

	logcroak "message" if !$pre_condition;

in regular code.

Over the years, the original authors found DATUM to be a very valuable
aid in large software, especially in situations where the bug tolerence
is zero: OS modules, DB access/replication modules.

Send bug reports, hints, tips, suggestions to Dave Hoover at
<squirrel@cpan.org>.
