=head1 VERSION
-Version 0.10
+Version 0.19
=cut
our $VERSION;
BEGIN {
- $VERSION = '0.10';
+ $VERSION = '0.19';
}
=head1 SYNOPSIS
package Scope;
- use Scope::Upper qw/reap localize localize_elem localize_delete :words/;
+ use Scope::Upper qw<
+ reap localize localize_elem localize_delete
+ :words
+ >;
sub new {
my ($class, $name) = @_;
package UserLand;
{
- Scope->new("top"); # initializes $UserLand::tag
+ Scope->new("top"); # initializes $UserLand::tag
{
Scope->catch;
- my $one = 1 + undef; # prints "top: Use of uninitialized value..."
+ my $one = 1 + undef; # prints "top: Use of uninitialized value..."
{
Scope->private;
eval { require Cwd };
- print $@; # prints "Can't locate Cwd.pm in @INC (@INC contains:) at..."
- }
+ print $@; # prints "Can't locate Cwd.pm in @INC
+ } # (@INC contains:) at..."
- require Cwd; # loads Cwd.pm
+ require Cwd; # loads Cwd.pm
}
- } # prints "top: done"
+ } # prints "top: done"
L</unwind> and L</want_at> :
package Try;
- use Scope::Upper qw/unwind want_at :words/;
+ use Scope::Upper qw<unwind want_at :words>;
sub try (&) {
my @result = shift->();
sub zap {
try {
- my @things = qw/a b c/;
+ my @things = qw<a b c>;
return @things; # returns to try() and then outside zap()
# not reached
};
# not reached
}
- my @stuff = zap(); # @stuff contains qw/a b c/
+ my @stuff = zap(); # @stuff contains qw<a b c>
my $stuff = zap(); # $stuff contains 3
+L</uplevel> :
+
+ package Uplevel;
+
+ use Scope::Upper qw<uplevel CALLER>;
+
+ sub target {
+ faker(@_);
+ }
+
+ sub faker {
+ uplevel {
+ my $sub = (caller 0)[3];
+ print "$_[0] from $sub()";
+ } @_ => CALLER(1);
+ }
+
+ 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 *
-return values immediately to an upper level with L</unwind>, and know which context was in use then with L</want_at>.
+return values immediately to an upper level with L</unwind>, L</yield> and L</leave>, and know which context was in use then with L</want_at> ;
+
+=item *
+
+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
XSLoader::load(__PACKAGE__, $VERSION);
}
-=head2 C<reap $callback, $context>
+=head2 C<reap>
+
+ reap { ... };
+ reap { ... } $context;
+ &reap($callback, $context);
Adds a destructor that calls C<$callback> (in void context) when the upper scope represented by C<$context> ends.
-=head2 C<localize $what, $value, $context>
+=head2 C<localize>
+
+ localize $what, $value;
+ localize $what, $value, $context;
Introduces a C<local> delayed to the time of first return into the upper scope denoted by C<$context>.
C<$what> can be :
will set C<$x> to a reference to the string C<'foo'>.
Other sigils (C<'@'>, C<'%'>, C<'&'> and C<'*'>) require C<$value> to be a reference of the corresponding type.
-When the symbol is given by a string, it is resolved when the actual localization takes place and not when C<localize> is called.
-Thus, if the symbol name is not qualified, it will refer to the variable in the package where the localization actually takes place and not in the one where the C<localize> call was compiled.
+When the symbol is given by a string, it is resolved when the actual localization takes place and not when L</localize> is called.
+Thus, if the symbol name is not qualified, it will refer to the variable in the package where the localization actually takes place and not in the one where the L</localize> call was compiled.
For example,
{
=back
-=head2 C<localize_elem $what, $key, $value, $context>
+=head2 C<localize_elem>
+
+ localize_elem $what, $key, $value;
+ localize_elem $what, $key, $value, $context;
Introduces a C<local $what[$key] = $value> or C<local $what{$key} = $value> delayed to the time of first return into the upper scope denoted by C<$context>.
-Just like for L</localize>, the type of localization is determined from which kind of reference C<$value> is when C<$what> is a glob, and from the sigil when it's a string.
+Unlike L</localize>, C<$what> must be a string and the type of localization is inferred from its sigil.
+The two only valid types are array and hash ; for anything besides those, L</localize_elem> will throw an exception.
C<$key> is either an array index or a hash key, depending of which kind of variable you localize.
If C<$what> is a string pointing to an undeclared variable, the variable will be vivified as soon as the localization occurs and emptied when it ends, although it will still exist in its glob.
-=head2 C<localize_delete $what, $key, $context>
+=head2 C<localize_delete>
+
+ localize_delete $what, $key;
+ localize_delete $what, $key, $context;
Introduces the deletion of a variable or an array/hash element delayed to the time of first return into the upper scope denoted by C<$context>.
C<$what> can be:
=back
-=head2 C<unwind @values, $context>
+=head2 C<unwind>
+
+ unwind;
+ unwind @values, $context;
-Returns C<@values> I<from> the context pointed by C<$context>, i.e. from the subroutine, eval or format at or just above C<$context>, and immediately restart the program flow at this point - thus effectively returning to an upper scope.
+Returns C<@values> I<from> the subroutine, eval or format context pointed by or just above C<$context>, and immediately restart the program flow at this point - thus effectively returning C<@values> to an upper scope.
+If C<@values> is empty, then the C<$context> parameter is optional and defaults to the current context (making the call equivalent to a bare C<return;>) ; otherwise it is mandatory.
The upper context isn't coerced onto C<@values>, which is hence always evaluated in list context.
This means that
will set C<$num> to C<'z'>.
You can use L</want_at> to handle these cases.
-=head2 C<want_at $context>
+=head2 C<yield>
+
+ yield;
+ yield @values, $context;
+
+Returns C<@values> I<from> the context pointed by or just above C<$context>, and immediately restart the program flow at this point.
+If C<@values> is empty, then the C<$context> parameter is optional and defaults to the current context ; otherwise it is mandatory.
+
+L</yield> differs from L</unwind> in that it can target I<any> upper scope (besides a C<s///e> substitution context) and not necessarily a sub, an eval or a format.
+Hence you can use it to return values from a C<do> or a C<map> block :
+
+ my $now = do {
+ local $@;
+ eval { require Time::HiRes } or yield time() => HERE;
+ Time::HiRes::time();
+ };
+
+ my @uniq = map {
+ yield if $seen{$_}++; # returns the empty list from the block
+ ...
+ } @things;
+
+Like for L</unwind>, the upper context isn't coerced onto C<@values>.
+
+=head2 C<leave>
+
+ leave;
+ leave @values;
+
+Immediately returns C<@values> from the current block, whatever it may be (besides a C<s///e> substitution context).
+C<leave> is actually a synonym for C<unwind HERE>, while C<leave @values> is a synonym for C<yield @values, HERE>.
+
+=head2 C<want_at>
+
+ my $want = want_at;
+ my $want = want_at $context;
Like C<wantarray>, but for the subroutine/eval/format at or just above C<$context>.
will rightfully set C<$num> to C<26>.
+=head2 C<uplevel>
+
+ my @ret = uplevel { ...; return @ret };
+ my @ret = uplevel { my @args = @_; ...; return @ret } @args, $context;
+ my @ret = &uplevel($callback, @args, $context);
+
+Executes the code reference C<$callback> with arguments C<@args> as if it were located at the subroutine stack frame pointed by C<$context>, effectively fooling C<caller> and C<die> into believing that the call actually happened higher in the stack.
+The code is executed in the context of the C<uplevel> call, and what it returns is returned as-is by C<uplevel>.
+
+ sub target {
+ faker(@_);
+ }
+
+ sub faker {
+ uplevel {
+ map { 1 / $_ } @_;
+ } @_ => CALLER(1);
+ }
+
+ my @inverses = target(1, 2, 4); # @inverses contains (0, 0.5, 0.25)
+ my $count = target(1, 2, 4); # $count is 3
+
+Note that if C<@args> is empty, then the C<$context> parameter is optional and defaults to the current context ; otherwise it is mandatory.
+
+L<Sub::Uplevel> also implements a pure-Perl version of C<uplevel>.
+Both are identical, with the following caveats :
+
+=over 4
+
+=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 can only uplevel to a B<subroutine> stack frame, and will croak if you try to target an C<eval> or a format.
+
+=item *
+
+Exceptions thrown from the code called by this version of C<uplevel> will not be caught by C<eval> blocks between the target frame and the uplevel call, while they will for L<Sub::Uplevel>'s version.
+This means that :
+
+ eval {
+ sub {
+ local $@;
+ eval {
+ sub {
+ uplevel { die 'wut' } CALLER(2); # for Scope::Upper
+ # uplevel(3, sub { die 'wut' }) # for Sub::Uplevel
+ }->();
+ };
+ print "inner block: $@";
+ $@ and exit;
+ }->();
+ };
+ print "outer block: $@";
+
+will print "inner block: wut..." with L<Sub::Uplevel> and "outer block: wut..." with L<Scope::Upper>.
+
+=item *
+
+L<Sub::Uplevel> globally overrides the Perl keyword C<caller>, while L<Scope::Upper> does not.
+
+=back
+
+A simple wrapper lets you mimic the interface of L<Sub::Uplevel/uplevel> :
+
+ use Scope::Upper;
+
+ sub uplevel {
+ my $frame = shift;
+ my $code = shift;
+ my $cxt = Scope::Upper::CALLER($frame);
+ &Scope::Upper::uplevel($code => @_ => $cxt);
+ }
+
+Albeit the three exceptions listed above, it passes all the tests of L<Sub::Uplevel>.
+
+=head2 C<uid>
+
+ my $uid = uid;
+ my $uid = 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>
+
+ my $is_valid = 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>
=head3 C<TOP>
+ my $top_context = TOP;
+
Returns the context that currently represents the highest scope.
=head3 C<HERE>
+ my $current_context = HERE;
+
The context of the current scope.
=head2 Getting a context from a context
For any of those functions, C<$from> is expected to be a context.
When omitted, it defaults to the the current context.
-=head3 C<UP $from>
+=head3 C<UP>
+
+ my $upper_context = UP;
+ my $upper_context = UP $from;
The context of the scope just above C<$from>.
-=head3 C<SUB $from>
+=head3 C<SUB>
+
+ my $sub_context = SUB;
+ my $sub_context = SUB $from;
The context of the closest subroutine above C<$from>.
Note that C<$from> is returned if it is already a subroutine context ; hence C<SUB SUB == SUB>.
-=head3 C<EVAL $from>
+=head3 C<EVAL>
+
+ my $eval_context = EVAL;
+ my $eval_context = EVAL $from;
The context of the closest eval above C<$from>.
Note that C<$from> is returned if it is already an eval context ; hence C<EVAL EVAL == EVAL>.
Here, C<$level> should denote a number of scopes above the current one.
When omitted, it defaults to C<0> and those functions return the same context as L</HERE>.
-=head3 C<SCOPE $level>
+=head3 C<SCOPE>
+
+ my $context = SCOPE;
+ my $context = SCOPE $level;
The C<$level>-th upper context, regardless of its type.
-=head3 C<CALLER $level>
+=head3 C<CALLER>
+
+ my $context = CALLER;
+ my $context = CALLER $level;
The context of the C<$level>-th upper subroutine/eval/format.
It kind of corresponds to the context represented by C<caller $level>, but while e.g. C<caller 0> refers to the caller context, C<CALLER 0> will refer to the top scope in the current context.
{
reap \&cleanup => $cxt;
...
- } # $cxt = SCOPE(0), or HERE
+ } # $cxt = SCOPE(0) = HERE
...
- }->(); # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0)
+ }->(); # $cxt = SCOPE(1) = UP = SUB = CALLER(0)
...
- }; # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1)
+ }; # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1)
...
- }->(); # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2)
+ }->(); # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2)
...
Where L</localize>, L</localize_elem> and L</localize_delete> act depending on the C<$cxt> :
sub {
{
localize '$x' => 1 => $cxt;
- # $cxt = SCOPE(0), or HERE
+ # $cxt = SCOPE(0) = HERE
...
}
- # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0)
+ # $cxt = SCOPE(1) = UP = SUB = CALLER(0)
...
}->();
- # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1)
+ # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1)
...
};
- # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2)
+ # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2)
...
}->();
- # $cxt = SCOPE(4), UP SUB UP SUB, or UP SUB EVAL, or UP CALLER(2), or TOP
+ # $cxt = SCOPE(4), UP SUB UP SUB = UP SUB EVAL = UP CALLER(2) = TOP
...
-Where L</unwind> and L</want_at> point to depending on the C<$cxt>:
+Where L</unwind>, L</yield>, L</want_at> and L</uplevel> point to depending on the C<$cxt>:
sub {
eval {
sub {
{
- unwind @things => $cxt;
+ unwind @things => $cxt; # or yield @things => $cxt
+ # or uplevel { ... } $cxt
...
}
...
- }->(); # $cxt = SCOPE(0 .. 1), or HERE, or UP, or SUB, or CALLER(0)
+ }->(); # $cxt = SCOPE(0) = SCOPE(1) = HERE = UP = SUB = CALLER(0)
...
- }; # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1)
+ }; # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1) (*)
...
- }->(); # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2)
+ }->(); # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2)
...
+ # (*) Note that uplevel() will croak if you pass that scope frame,
+ # because it cannot target eval scopes.
+
=head1 EXPORT
-The functions L</reap>, L</localize>, L</localize_elem>, L</localize_delete>, L</unwind> and L</want_at> are only exported on request, either individually or by the tags C<':funcs'> and C<':all'>.
+The functions L</reap>, L</localize>, L</localize_elem>, L</localize_delete>, L</unwind>, L</yield>, L</leave>, L</want_at> and L</uplevel> are only exported on request, either individually or by the tags C<':funcs'> and C<':all'>.
The constant L</SU_THREADSAFE> is also only exported on request, individually or by the tags C<':consts'> and C<':all'>.
=cut
-use base qw/Exporter/;
+use base qw<Exporter>;
our @EXPORT = ();
our %EXPORT_TAGS = (
- funcs => [ qw/reap localize localize_elem localize_delete unwind want_at/ ],
- words => [ qw/TOP HERE UP SUB EVAL SCOPE CALLER/ ],
- consts => [ qw/SU_THREADSAFE/ ],
+ funcs => [ qw<
+ reap
+ localize localize_elem localize_delete
+ unwind yield leave
+ want_at
+ uplevel
+ uid validate_uid
+ > ],
+ words => [ qw<TOP HERE UP SUB EVAL SCOPE CALLER> ],
+ consts => [ qw<SU_THREADSAFE> ],
);
our @EXPORT_OK = map { @$_ } values %EXPORT_TAGS;
$EXPORT_TAGS{'all'} = [ @EXPORT_OK ];
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<perl> 5.6.
+
+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.
+
+L<XSLoader> (core since perl 5.006).
=head1 SEE ALSO
+L<perlfunc/local>, L<perlsub/"Temporary Values via local()">.
+
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>.
+
=head1 AUTHOR
Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
=head1 COPYRIGHT & LICENSE
-Copyright 2008,2009,2010 Vincent Pit, all rights reserved.
+Copyright 2008,2009,2010,2011,2012 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.