1 package Lexical::Types;
10 Lexical::Types - Extend the semantics of typed lexicals.
28 package My::Types::Str;
30 sub new { bless { }, shift }
33 use Lexical::Types as => sub { 'My::Types::' . $_[0] => 'new' };
35 my Str $x; # $x is now a My::Types::Str object
38 package My::Types::Int;
40 sub TYPEDSCALAR { bless { }, shift }
45 use constant Int => 'My::Types::Int';
47 my Int $y; # $y is now a My::Types::Int object
51 This pragma allows you to hook the execution of typed lexicals declarations (C<my Str $x>) by calling a configurable method in a configurable package at each run.
52 In particular, it can be used to automatically tie or bless typed lexicals whenever they are initialized.
54 Remind that for C<perl> to be able to parse C<my Str $x>, you need :
60 either the C<Str> package to be defined ;
64 or for C<Str> to be a constant sub returning a valid defined package.
68 so make sure you follow one of those two strategies to define your types.
70 This pragma is B<not> implemented with a source filter.
76 XSLoader::load(__PACKAGE__, $VERSION);
81 =head2 C<< import [ as => [ $prefix | $mangler ] ] >>
83 Magically called when writing C<use Lexical::Types>.
84 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.
85 The method and package are determined by the parameter C<'as'> :
91 If it's left unspecified, the C<TYPEDSCALAR> method in the C<Str> package will be called.
94 my Str $x; # calls Str->TYPEDSCALAR
98 If a plain scalar C<$prefix> is passed as the value, the C<TYPEDSCALAR> method in the C<${prefix}::Str> package will be used.
100 use Lexical::Types as => 'My::'; # or "as => 'My'"
101 my Str $x; # calls My::Str->TYPEDSCALAR
105 If the value given is a code reference C<$mangler>, it will be called at compile-time with arguments C<'Str'> and C<'TYPEDSCALAR'> and is expected to return :
111 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) ;
113 use Lexical::Types as => sub { return $_[0] =~ /Str/ ? @_ : () };
114 my Str $y; # calls Str->TYPEDSCALAR
115 my Int $x; # nothing special
119 or the desired package and method name, in that order (if any of those is C<undef>, the default value will be used instead).
121 use Lexical::Types as => sub { 'My', 'new_' . lc($_[0]) };
122 my Str $x; # the coderef indicates to call My->new_str
126 Note that if the type is a constant, C<$_[0]> will be set to the I<value> of constant and not to its name.
128 use Lexical::Types as => sub { $_[0] => 'new' };
129 use constant Str => 'MyStr';
130 my Str $x; # calls MyStr->new
132 This means in particular that you can't both use constant types and redirect several types to different methods of the same package, because then you can't distinguish between the original types with C<$_[0]>.
144 my $as = delete $args{'as'};
150 $as .= '::' if $as !~ /::$/;
151 $hint = _tag(sub { $as . $_[0] });
154 Carp::croak("Invalid $r reference for 'as'");
157 $hint = _tag(sub { @_ });
161 # Yes, we store a coderef inside the hints hash, but that's just for compile
163 $^H{+(__PACKAGE__)} = $hint;
168 Magically called when writing C<no Lexical::Types>.
169 Turns the pragma off.
174 $^H{+(__PACKAGE__)} = undef;
177 =head1 RUN-TIME INITIALIZER METHOD
179 The initializer method receives an alias to the pad slot of the initialized lexical in C<$_[1]> and the original type name in C<$_[2]>.
180 You can either edit C<$_[1]> in place, in which case you should return an empty list, or return a new scalar that will be copied into the pad slot.
182 use Lexical::Types as => 'My';
188 sub My::Str::TYPEDSCALAR {
189 # $_[1] is an alias to $x, and $_[2] is 'Str'
195 You can integrate L<Lexical::Types> in your module so that using it will provide types to your users without asking them to load either L<Lexical::Types> or the type classes manually.
199 BEGIN { require Lexical::Types; }
202 eval 'package Str; package Int'; # The types you want to support
203 Lexical::Types->import(
204 as => sub { __PACKAGE__, 'new_' . lc($_[0]) }
209 Lexical::Types->unimport;
216 If you prefer to use constants rather than creating empty packages, you can replace the previous example with something like this :
220 BEGIN { require Lexical::Types; }
225 my $type = __PACKAGE__ . '::' . $_;
227 no warnings 'redefine';
228 *{$pkg.'::'.$_} = eval "sub () { '$type' }";
230 Lexical::Types->import(
231 as => sub { $_[0] => 'new' }
236 Lexical::Types->unimport;
239 package MyTypes::Str;
243 package MyTypes::Int;
249 =head2 C<LT_THREADSAFE>
251 True iff the module could have been built with thread-safety features enabled.
253 =head2 C<LT_FORKSAFE>
255 True iff this module could have been built with fork-safety features enabled.
256 This will always be true except on Windows where it's false for perl 5.10.0 and below .
260 The restrictions on the type (being either a defined package name or a constant) 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.
262 Only one mangler or prefix can be in use at the same time in a given scope.
264 The implementation was tweaked to work around several limitations of vanilla C<perl> pragmas : it's thread safe, and doesn't suffer from a C<perl 5.8.x-5.10.0> bug that causes all pragmas to propagate into C<require>d scopes.
266 With 5.8 perls, the pragma does not propagate into C<eval STRING>.
267 This is due to a shortcoming in the way perl handles the hints hash, which is addressed in perl 5.10.
274 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.
276 L<XSLoader> (standard since perl 5.006).
282 L<Attribute::Handlers>.
286 Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
288 You can contact me by mail or on C<irc.perl.org> (vincent).
292 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>.
293 I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
297 You can find documentation for this module with the perldoc command.
299 perldoc Lexical::Types
301 Tests code coverage report is available at L<http://www.profvince.com/perl/cover/Lexical-Types>.
303 =head1 ACKNOWLEDGEMENTS
305 Inspired by Ricardo Signes.
307 Thanks Florian Ragwitz for suggesting the use of constants for types.
309 =head1 COPYRIGHT & LICENSE
311 Copyright 2009,2010,2011 Vincent Pit, all rights reserved.
313 This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
317 1; # End of Lexical::Types