1 package Lexical::Types;
12 Lexical::Types - Extend the semantics of typed lexicals.
30 package My::Types::Str;
32 sub new { bless { }, shift }
35 use Lexical::Types as => sub { 'My::Types::' . $_[0] => 'new' };
37 my Str $x; # $x is now a My::Types::Str object
40 package My::Types::Int;
42 sub TYPEDSCALAR { bless { }, shift }
47 use constant Int => 'My::Types::Int';
49 my Int $y; # $y is now a My::Types::Int object
53 This pragma allows you to hook the execution of typed lexicals declarations (C<my Str $x>).
54 In particular, it can be used to automatically tie or bless typed lexicals.
56 It is B<not> implemented with a source filter.
62 XSLoader::load(__PACKAGE__, $VERSION);
67 =head2 C<< import [ as => [ $prefix | $mangler ] ] >>
69 Magically called when writing C<use Lexical::Types>.
70 All the occurences of C<my Str $x> in the current lexical scope will be changed to call at each run a given method in a given package.
71 The method and package are determined by the parameter C<'as'> :
77 If it's left unspecified, the C<TYPEDSCALAR> method in the C<Str> package will be called.
80 my Str $x; # calls Str->TYPEDSCALAR
84 If a plain scalar C<$prefix> is passed as the value, the C<TYPEDSCALAR> method in the C<${prefix}::Str> package will be used.
86 use Lexical::Types as => 'My::'; # or "as => 'My'"
87 my Str $x; # calls My::Str->TYPEDSCALAR
91 If the value given is a code reference C<$mangler>, it will be called at compile-time with arguments C<'Str'> and C<'TYPEDSCALAR'> and is expected to return :
97 either an empty list, in which case the current typed lexical definition will be skipped (thus it won't be altered to trigger a run-time hook) ;
99 use Lexical::Types as => sub { return $_[0] =~ /Str/ ? @_ : () };
100 my Str $y; # calls Str->TYPEDSCALAR
101 my Int $x; # nothing special
105 or the desired package and method name, in that order (if any of those is C<undef>, the default value will be used instead).
107 use Lexical::Types as => sub { 'My', 'new_' . lc($_[0]) };
108 my Str $x; # the coderef indicates to call My->new_str
114 The initializer method receives an alias to the pad entry of C<$x> in C<$_[1]> and the original type name (C<Str>) in C<$_[2]>.
115 You can either edit C<$_[1]> in place, in which case you should return an empty list, or return a new scalar that will be copied into C<$x>.
125 my $as = delete $args{'as'};
131 $as .= '::' if $as !~ /::$/;
132 $hint = _tag(sub { $as . $_[0] });
134 croak "Invalid $r reference for 'as'";
141 # Yes, we store a coderef inside the hints hash, but that's just for compile
143 $^H{+(__PACKAGE__)} = $hint;
148 Magically called when writing C<no Lexical::Types>.
149 Turns the pragma off.
154 $^H{+(__PACKAGE__)} = undef;
159 You can integrate L<Lexical::Types> in your module so that using it will provide types to your users without asking them to load either L<Lexical::Types> or the type classes manually.
163 BEGIN { require Lexical::Types; }
166 eval 'package Str; package Int'; # The types you want to support
167 Lexical::Types->import(
168 as => sub { __PACKAGE__, 'new_' . lc($_[0]) }
173 Lexical::Types->unimport;
182 For C<perl> to be able to parse C<my Str $x>, you need :
188 either the C<Str> package to be defined ;
192 or for C<Str> to be a constant sub returning a valid defined package.
196 Those restrictions apply even if you use the C<'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.
198 Only one mangler or prefix can be in use at the same time in a given scope.
202 L<perl> 5.8, L<XSLoader>.
208 L<Attribute::Handlers>.
212 Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
214 You can contact me by mail or on C<irc.perl.org> (vincent).
218 Please report any bugs or feature requests to C<bug-lexical-types at rt.cpan.org>, or through the web interface at L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Lexical-Types>. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
222 You can find documentation for this module with the perldoc command.
224 perldoc Lexical::Types
226 Tests code coverage report is available at L<http://www.profvince.com/perl/cover/Lexical-Types>.
228 =head1 ACKNOWLEDGEMENTS
230 Inspired by Ricardo Signes.
232 Thanks Florian Ragwitz for suggesting the use of constants for types.
234 =head1 COPYRIGHT & LICENSE
236 Copyright 2009 Vincent Pit, all rights reserved.
238 This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
242 1; # End of Lexical::Types