=head1 VERSION
-Version 0.15
+Version 0.17
=cut
our $VERSION;
BEGIN {
- $VERSION = '0.15';
+ $VERSION = '0.17';
}
=head1 SYNOPSIS
target('hello'); # "hello from Uplevel::target()"
+L</uid> and L</validate_uid> :
+
+ use Scope::Upper qw<uid validate_uid>;
+
+ my $uid;
+
+ {
+ $uid = uid();
+ {
+ if ($uid eq uid(UP)) { # yes
+ ...
+ }
+ if (validate_uid($uid)) { # yes
+ ...
+ }
+ }
+ }
+
+ if (validate_uid($uid)) { # no
+ ...
+ }
+
=head1 DESCRIPTION
This module lets you defer actions I<at run-time> that will take place when the control flow returns into an upper scope.
=item *
-execute a subroutine in the context of an upper subroutine stack frame with L</uplevel>.
+execute a subroutine in the setting of an upper subroutine stack frame with L</uplevel> ;
+
+=item *
+
+uniquely identify contextes with L</uid> and L</validate_uid>.
=back
}
my @inverses = target(1, 2, 4); # @inverses contains (0, 0.5, 0.25)
- my $count = target(1, 2, 4); # $target is 3
+ my $count = target(1, 2, 4); # $count is 3
L<Sub::Uplevel> also implements a pure-Perl version of C<uplevel>.
Both are identical, with the following caveats :
=item *
The L<Sub::Uplevel> implementation of C<uplevel> may execute a code reference in the context of B<any> upper stack frame.
-The L<Scope::Upper> version only allows to uplevel to a B<subroutine> stack frame, and will croak if you try to target an C<eval> or a format.
+The L<Scope::Upper> version can only uplevel to a B<subroutine> stack frame, and will croak if you try to target an C<eval> or a format.
=item *
=item *
-L<Sub::Uplevel> globally overrides C<CORE::GLOBAL::caller>, while L<Scope::Upper> does not.
+L<Sub::Uplevel> globally overrides the Perl keyword C<caller>, while L<Scope::Upper> does not.
=back
Albeit the three exceptions listed above, it passes all the tests of L<Sub::Uplevel>.
+=head2 C<uid $context>
+
+Returns an unique identifier (UID) for the context (or dynamic scope) pointed by C<$context>, or for the current context if C<$context> is omitted.
+This UID will only be valid for the life time of the context it represents, and another UID will be generated next time the same scope is executed.
+
+ my $uid;
+
+ {
+ $uid = uid;
+ if ($uid eq uid()) { # yes, this is the same context
+ ...
+ }
+ {
+ if ($uid eq uid()) { # no, we are one scope below
+ ...
+ }
+ if ($uid eq uid(UP)) { # yes, UP points to the same scope as $uid
+ ...
+ }
+ }
+ }
+
+ # $uid is now invalid
+
+ {
+ if ($uid eq uid()) { # no, this is another block
+ ...
+ }
+ }
+
+For example, each loop iteration gets its own UID :
+
+ my %uids;
+
+ for (1 .. 5) {
+ my $uid = uid;
+ $uids{$uid} = $_;
+ }
+
+ # %uids has 5 entries
+
+The UIDs are not guaranteed to be numbers, so you must use the C<eq> operator to compare them.
+
+To check whether a given UID is valid, you can use the L</validate_uid> function.
+
+=head2 C<validate_uid $uid>
+
+Returns true if and only if C<$uid> is the UID of a currently valid context (that is, it designates a scope that is higher than the current one in the call stack).
+
+ my $uid;
+
+ {
+ $uid = uid();
+ if (validate_uid($uid)) { # yes
+ ...
+ }
+ {
+ if (validate_uid($uid)) { # yes
+ ...
+ }
+ }
+ }
+
+ if (validate_uid($uid)) { # no
+ ...
+ }
+
=head1 CONSTANTS
=head2 C<SU_THREADSAFE>
...
# (*) Note that uplevel() will croak if you pass that scope frame,
- # because it can't target eval scopes.
+ # because it cannot target eval scopes.
=head1 EXPORT
localize localize_elem localize_delete
unwind want_at
uplevel
+ uid validate_uid
> ],
words => [ qw<TOP HERE UP SUB EVAL SCOPE CALLER> ],
consts => [ qw<SU_THREADSAFE> ],
Some rare oddities may still happen when running inside the debugger.
It may help to use a perl higher than 5.8.9 or 5.10.0, as they contain some context-related fixes.
+Calling C<goto> to replace an L</uplevel>'d code frame does not work :
+
+=over 4
+
+=item *
+
+for a C<perl> older than the 5.8 series ;
+
+=item *
+
+for a C<DEBUGGING> C<perl> run with debugging flags set (as in C<perl -D ...>) ;
+
+=item *
+
+when the runloop callback is replaced by another module.
+
+=back
+
+In those three cases, L</uplevel> will look for a C<goto &sub> statement in its callback and, if there is one, throw an exception before executing the code.
+
+Moreover, in order to handle C<goto> statements properly, L</uplevel> currently has to suffer a run-time overhead proportional to the size of the the callback in every case (with a small ratio), and proportional to the size of B<all> the code executed as the result of the L</uplevel> call (including subroutine calls inside the callback) when a C<goto> statement is found in the L</uplevel> callback.
+Despite this shortcoming, this XS version of L</uplevel> should still run way faster than the pure-Perl version from L<Sub::Uplevel>.
+
=head1 DEPENDENCIES
L<XSLoader> (standard since perl 5.006).
L<Alias>, L<Hook::Scope>, L<Scope::Guard>, L<Guard>.
+L<Sub::Uplevel>.
+
L<Continuation::Escape> is a thin wrapper around L<Scope::Upper> that gives you a continuation passing style interface to L</unwind>.
It's easier to use, but it requires you to have control over the scope where you want to return.
L<Scope::Escape>.
-L<Sub::Uplevel> provides a pure-Perl implementation of L</uplevel>.
-
=head1 AUTHOR
Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
projects / perl / modules / Scope-Upper.git / blobdiff