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);
84 use Lexical::Types as => $prefix;
85 use Lexical::Types as => sub { ... }; # = $mangler
87 Magically called when C<use Lexical::Types> is encountered.
88 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.
89 The method and package are determined by the parameter C<'as'> :
95 If it's left unspecified, the C<TYPEDSCALAR> method in the C<Str> package will be called.
98 my Str $x; # calls Str->TYPEDSCALAR
102 If a plain scalar C<$prefix> is passed as the value, the C<TYPEDSCALAR> method in the C<${prefix}::Str> package will be used.
104 use Lexical::Types as => 'My::'; # or "as => 'My'"
105 my Str $x; # calls My::Str->TYPEDSCALAR
109 If the value given is a code reference C<$mangler>, it will be called at compile-time with arguments C<'Str'> and C<'TYPEDSCALAR'> and is expected to return :
115 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) ;
117 use Lexical::Types as => sub { return $_[0] =~ /Str/ ? @_ : () };
118 my Str $y; # calls Str->TYPEDSCALAR
119 my Int $x; # nothing special
123 or the desired package and method name, in that order (if any of those is C<undef>, the default value will be used instead).
125 use Lexical::Types as => sub { 'My', 'new_' . lc($_[0]) };
126 my Str $x; # the coderef indicates to call My->new_str
130 Note that if the type is a constant, C<$_[0]> will be set to the I<value> of constant and not to its name.
132 use Lexical::Types as => sub { $_[0] => 'new' };
133 use constant Str => 'MyStr';
134 my Str $x; # calls MyStr->new
136 This means in particular that you can't both use constant types and redirect several types to different methods of the same package, because then you can't distinguish between the original types with C<$_[0]>.
148 my $as = delete $args{'as'};
154 $as .= '::' if $as !~ /::$/;
155 $hint = _tag(sub { $as . $_[0] });
158 Carp::croak("Invalid $r reference for 'as'");
161 $hint = _tag(sub { @_ });
165 # Yes, we store a coderef inside the hints hash, but that's just for compile
167 $^H{+(__PACKAGE__)} = $hint;
174 Magically called when C<no Lexical::Types> is encountered.
175 Turns the pragma off.
180 $^H{+(__PACKAGE__)} = undef;
183 =head1 RUN-TIME INITIALIZER METHOD
185 The initializer method receives an alias to the pad slot of the initialized lexical in C<$_[1]> and the original type name in C<$_[2]>.
186 You can either edit C<$_[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.
188 use Lexical::Types as => 'My';
194 sub My::Str::TYPEDSCALAR {
195 # $_[1] is an alias to $x, and $_[2] is 'Str'
201 You can integrate L<Lexical::Types> in your module so that using it will provide types to your users without asking them to load either L<Lexical::Types> or the type classes manually.
205 BEGIN { require Lexical::Types; }
208 eval 'package Str; package Int'; # The types you want to support
209 Lexical::Types->import(
210 as => sub { __PACKAGE__, 'new_' . lc($_[0]) }
215 Lexical::Types->unimport;
222 If you prefer to use constants rather than creating empty packages, you can replace the previous example with something like this :
226 BEGIN { require Lexical::Types; }
231 my $type = __PACKAGE__ . '::' . $_;
233 no warnings 'redefine';
234 *{$pkg.'::'.$_} = eval "sub () { '$type' }";
236 Lexical::Types->import(
237 as => sub { $_[0] => 'new' }
242 Lexical::Types->unimport;
245 package MyTypes::Str;
249 package MyTypes::Int;
255 =head2 C<LT_THREADSAFE>
257 True iff the module could have been built with thread-safety features enabled.
259 =head2 C<LT_FORKSAFE>
261 True iff this module could have been built with fork-safety features enabled.
262 This will always be true except on Windows where it's false for perl 5.10.0 and below .
266 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.
268 Only one mangler or prefix can be in use at the same time in a given scope.
270 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.
272 With 5.8 perls, the pragma does not propagate into C<eval STRING>.
273 This is due to a shortcoming in the way perl handles the hints hash, which is addressed in perl 5.10.
280 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.
282 L<XSLoader> (standard since perl 5.006).
288 L<Attribute::Handlers>.
292 Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
294 You can contact me by mail or on C<irc.perl.org> (vincent).
298 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>.
299 I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
303 You can find documentation for this module with the perldoc command.
305 perldoc Lexical::Types
307 Tests code coverage report is available at L<http://www.profvince.com/perl/cover/Lexical-Types>.
309 =head1 ACKNOWLEDGEMENTS
311 Inspired by Ricardo Signes.
313 Thanks Florian Ragwitz for suggesting the use of constants for types.
315 =head1 COPYRIGHT & LICENSE
317 Copyright 2009,2010,2011 Vincent Pit, all rights reserved.
319 This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
323 1; # End of Lexical::Types