From: Vincent Pit <vince@profvince.com>
Date: Tue, 17 Feb 2009 00:52:18 +0000 (+0100)
Subject: A clearer introduction to magic
X-Git-Tag: v0.31~9
X-Git-Url: http://git.vpit.fr/?p=perl%2Fmodules%2FVariable-Magic.git;a=commitdiff_plain;h=3ed7c4d2c3b930e70e9006db2b902a47d98b775b

A clearer introduction to magic
---

diff --git a/lib/Variable/Magic.pm b/lib/Variable/Magic.pm
index 4456efb..50ada38 100644
--- a/lib/Variable/Magic.pm
+++ b/lib/Variable/Magic.pm
@@ -36,28 +36,49 @@ BEGIN {
 =head1 DESCRIPTION
 
 Magic is Perl way of enhancing objects.
-This mechanism let the user add extra data to any variable and hook syntaxical operations (such as access, assignation or destruction) that can be applied to it.
-With this module, you can add your own magic to any variable without the pain of the C API.
+This mechanism lets the user add extra data to any variable and hook syntaxical operations (such as access, assignation or destruction) that can be applied to it.
+With this module, you can add your own magic to any variable without having to write a single line of XS.
 
-Magic differs from tieing and overloading in several ways :
+You'll realize that these magic variables look a lot like tied variables.
+It's not surprising, as tied variables are implemented as a special kind of magic, just like any 'irregular' Perl variable : scalars like C<$!>, C<$(> or C<$^W>, the C<%ENV> and C<%SIG> hashes, the C<@ISA> array,  C<vec()> and C<substr()> lvalues, L<thread::shared> variables...
+They all share the same underlying C API, and this module gives you direct access to it.
+
+Still, the magic made available by this module differs from tieing and overloading in several ways :
 
 =over 4
 
 =item *
 
-Magic isn't copied on assignation (as for blessed references) : you attach it to variables, not values.
+It isn't copied on assignation.
+
+You attach it to variables, not values (as for blessed references).
 
 =item *
 
-It doesn't replace the original semantics : magic callbacks trigger before the original action take place, and can't prevent it to happen.
+It doesn't replace the original semantics.
+
+Magic callbacks trigger before the original action take place, and can't prevent it to happen.
+This makes catching individual events easier than with C<tie>, where you have to provide fallbacks methods for all actions by usually inheriting from the correct C<Tie::Std*> class and overriding individual methods in your own class.
 
 =item *
 
-It's mostly invisible at the Perl level : magical and non-magical variables cannot be distinguished with C<ref>, C<tied> or another trick.
+It's type-agnostic.
+
+The same magic can be applied on scalars, arrays, hashes, subs or globs.
+But the same hook (see below for a list) may trigger differently depending on the the type of the variable.
 
 =item *
 
-It's notably faster, since perl's way of handling magic is lighter by nature, and there's no need for any method resolution.
+It's mostly invisible at the Perl level.
+
+Magical and non-magical variables cannot be distinguished with C<ref>, C<tied> or another trick.
+
+=item *
+
+It's notably faster.
+
+Mainly because perl's way of handling magic is lighter by nature, and because there's no need for any method resolution.
+Also, since you don't have to reimplement all the variable semantics, you only pay for what you actually use.
 
 =back