Lexical::Types - Extend the semantics of typed lexicals.
VERSION
- Version 0.03
+ Version 0.12
SYNOPSIS
{ package Str; }
DESCRIPTION
This pragma allows you to hook the execution of typed lexicals
- declarations ("my Str $x"). In particular, it can be used to
- automatically tie or bless typed lexicals.
+ declarations ("my Str $x") by calling a configurable method in a
+ configurable package at each run. In particular, it can be used to
+ automatically tie or bless typed lexicals whenever they are initialized.
- It is not implemented with a source filter.
+ Remind that for "perl" to be able to parse "my Str $x", you need :
+
+ * either the "Str" package to be defined ;
+
+ * or for "Str" to be a constant sub returning a valid defined package.
+
+ so make sure you follow one of those two strategies to define your
+ types.
+
+ This pragma is not implemented with a source filter.
FUNCTIONS
"import [ as => [ $prefix | $mangler ] ]"
use Lexical::Types as => sub { 'My', 'new_' . lc($_[0]) };
my Str $x; # the coderef indicates to call My->new_str
- The initializer method receives an alias to the pad entry of $x in $_[1]
- and the original type name ("Str") in $_[2]. You can either edit $_[1]
- in place, in which case you should return an empty list, or return a new
- scalar that will be copied into $x.
+ Note that if the type is a constant, $_[0] will be set to the
+ *value* of constant and not to its name.
+
+ use Lexical::Types as => sub { $_[0] => 'new' };
+ use constant Str => 'MyStr';
+ my Str $x; # calls MyStr->new
+
+ This means in particular that you can't both use constant types and
+ redirect several types to different methods of the same package,
+ because then you can't distinguish between the original types with
+ $_[0].
"unimport"
Magically called when writing "no Lexical::Types". Turns the pragma off.
+RUN-TIME INITIALIZER METHOD
+ The initializer method receives an alias to the pad slot of the
+ initialized lexical in $_[1] and the original type name in $_[2]. You
+ can either edit $_[1] in place, in which case you should return an empty
+ list, or return a new scalar that will be copied into the pad slot.
+
+ use Lexical::Types as => 'My';
+
+ my Str $x;
+
+ ...
+
+ sub My::Str::TYPEDSCALAR {
+ # $_[1] is an alias to $x, and $_[2] is 'Str'
+ ...
+ }
+
INTEGRATION
You can integrate Lexical::Types in your module so that using it will
provide types to your users without asking them to load either
sub new_int { ... }
-CAVEATS
- For "perl" to be able to parse "my Str $x", you need :
+ If you prefer to use constants rather than creating empty packages, you
+ can replace the previous example with something like this :
- * either the "Str" package to be defined ;
+ package MyTypes;
- * or for "Str" to be a constant sub returning a valid defined package.
+ BEGIN { require Lexical::Types; }
- Those restrictions apply even if you use the 'as' option to redirect to
- another package, and are unlikely to find a workaround as this happens
- deep inside the lexer - far from the reach of an extension.
+ sub import {
+ my $pkg = caller;
+ for (qw<Str Int>) {
+ my $type = __PACKAGE__ . '::' . $_;
+ no strict 'refs';
+ no warnings 'redefine';
+ *{$pkg.'::'.$_} = eval "sub () { '$type' }";
+ }
+ Lexical::Types->import(
+ as => sub { $_[0] => 'new' }
+ );
+ }
+
+ sub unimport {
+ Lexical::Types->unimport;
+ }
+
+ package MyTypes::Str;
+
+ sub new { ... }
+
+ package MyTypes::Int;
+
+ sub new { ... }
+
+CONSTANTS
+ "LT_THREADSAFE"
+ True iff the module could have been built with thread-safety features
+ enabled.
+
+ "LT_FORKSAFE"
+ True iff this module could have been built with fork-safety features
+ enabled. This will always be true except on Windows where it's false for
+ perl 5.10.0 and below .
+
+CAVEATS
+ The restrictions on the type (being either a defined package name or a
+ constant) apply even if you use the 'as' option to redirect to another
+ package, and are unlikely to find a workaround as this happens deep
+ inside the lexer - far from the reach of an extension.
Only one mangler or prefix can be in use at the same time in a given
scope.
+ The implementation was tweaked to work around several limitations of
+ vanilla "perl" pragmas : it's thread safe, and doesn't suffer from a
+ "perl 5.8.x-5.10.0" bug that causes all pragmas to propagate into
+ "require"d scopes.
+
+ With 5.8 perls, the pragma does not propagate into "eval STRING". This
+ is due to a shortcoming in the way perl handles the hints hash, which is
+ addressed in perl 5.10.
+
DEPENDENCIES
- perl 5.8, XSLoader.
+ perl 5.8.3.
+
+ A C compiler. This module may happen to build with a C++ compiler as
+ well, but don't rely on it, as no guarantee is made in this regard.
+
+ XSLoader (standard since perl 5.006).
SEE ALSO
fields.
Thanks Florian Ragwitz for suggesting the use of constants for types.
COPYRIGHT & LICENSE
- Copyright 2009 Vincent Pit, all rights reserved.
+ Copyright 2009,2010,2011 Vincent Pit, all rights reserved.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
projects / perl / modules / Lexical-Types.git / blobdiff