package Scope::Upper;
+use 5.006_001;
+
use strict;
use warnings;
=head1 VERSION
-Version 0.17
+Version 0.27
=cut
our $VERSION;
BEGIN {
- $VERSION = '0.17';
+ $VERSION = '0.27';
}
=head1 SYNOPSIS
=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> ;
+
+=item *
+
+gather information about an upper context with L</want_at> and L</context_info> ;
=item *
=item *
-uniquely identify contextes with L</uid> and L</validate_uid>.
+uniquely identify contexts 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 :
=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>.
Unlike L</localize>, C<$what> must be a string and the type of localization is inferred from its sigil.
If C<$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:
=item *
-A string beginning with C<'@'> or C<'%'>, for which the call is equivalent to respectiveley C<local $a[$key]; delete $a[$key]> and C<local $h{$key}; delete $h{$key}>.
+A string beginning with C<'@'> or C<'%'>, for which the call is equivalent to respectively C<local $a[$key]; delete $a[$key]> and C<local $h{$key}; delete $h{$key}>.
=item *
=back
-=head2 C<unwind @values, $context>
+=head2 C<unwind>
-Returns C<@values> I<from> the context pointed by C<$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.
+ unwind;
+ unwind @values, $context;
+
+Returns C<@values> I<from> the subroutine, eval or format context pointed by or just above C<$context>, and immediately restarts 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 restarts 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>.
+You can use the fifth value returned by L</context_info> to handle context coercion.
+
+=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<yield HERE>, while C<leave @values> is a synonym for C<yield @values, HERE>.
-Like C<wantarray>, but for the subroutine/eval/format at or just above C<$context>.
+Like for L</yield>, you can use the fifth value returned by L</context_info> to handle context coercion.
-The previous example can then be "corrected" :
+=head2 C<want_at>
+
+ my $want = want_at;
+ my $want = want_at $context;
+
+Like L<perlfunc/wantarray>, but for the subroutine, eval or format context located at or just above C<$context>.
+
+It can be used to revise the example showed in L</unwind> :
my $num = sub {
my @a = ('a' .. 'z');
will rightfully set C<$num> to C<26>.
-=head2 C<uplevel $code, @args, $context>
+=head2 C<context_info>
+
+ my ($package, $filename, $line, $subroutine, $hasargs,
+ $wantarray, $evaltext, $is_require, $hints, $bitmask,
+ $hinthash) = context_info $context;
+
+Gives information about the context denoted by C<$context>, akin to what L<perlfunc/caller> provides but not limited only to subroutine, eval and format contexts.
+When C<$context> is omitted, it defaults to the current context.
+
+The returned values are, in order :
+
+=over 4
+
+=item *
+
+I<(index 0)> : the namespace in use when the context was created ;
+
+=item *
+
+I<(index 1)> : the name of the file at the point where the context was created ;
+
+=item *
+
+I<(index 2)> : the line number at the point where the context was created ;
+
+=item *
+
+I<(index 3)> : the name of the subroutine called for this context, or C<undef> if this is not a subroutine context ;
+
+=item *
+
+I<(index 4)> : a boolean indicating whether a new instance of C<@_> was set up for this context, or C<undef> if this is not a subroutine context ;
+
+=item *
+
+I<(index 5)> : the context (in the sense of L<perlfunc/wantarray>) in which the context (in our sense) is executed ;
+
+=item *
+
+I<(index 6)> : the contents of the string being compiled for this context, or C<undef> if this is not an eval context ;
-Executes the code reference C<$code> 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.
+=item *
+
+I<(index 7)> : a boolean indicating whether this eval context was created by C<require>, or C<undef> if this is not an eval context ;
+
+=item *
+
+I<(index 8)> : the value of the lexical hints in use when the context was created ;
+
+=item *
+
+I<(index 9)> : a bit string representing the warnings in use when the context was created ;
+
+=item *
+
+I<(index 10)> : a reference to the lexical hints hash in use when the context was created (only on perl 5.10 or greater).
+
+=back
+
+=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 {
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 :
Albeit the three exceptions listed above, it passes all the tests of L<Sub::Uplevel>.
-=head2 C<uid $context>
+=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.
To check whether a given UID is valid, you can use the L</validate_uid> function.
-=head2 C<validate_uid $uid>
+=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).
=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.
+When omitted, it defaults to the current context.
+
+=head3 C<UP>
-=head3 C<UP $from>
+ 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.
# $cxt = SCOPE(4), UP SUB UP SUB = UP SUB EVAL = UP CALLER(2) = TOP
...
-Where L</unwind>, L</want_at> and L</uplevel> point to depending on the C<$cxt>:
+Where L</unwind>, L</yield>, L</want_at>, L</context_info> and L</uplevel> point to depending on the C<$cxt>:
sub {
eval {
sub {
{
- unwind @things => $cxt; # or uplevel { ... } $cxt;
+ unwind @things => $cxt; # or yield @things => $cxt
+ # or uplevel { ... } $cxt
...
}
...
=head1 EXPORT
-The functions L</reap>, L</localize>, L</localize_elem>, L</localize_delete>, L</unwind>, L</want_at> and L</uplevel> 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>, L</context_info> 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'>.
funcs => [ qw<
reap
localize localize_elem localize_delete
- unwind want_at
+ unwind yield leave
+ want_at context_info
uplevel
uid validate_uid
> ],
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.
+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 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>.
+Starting from C<perl> 5.19.4, it is unfortunately no longer possible to reliably throw exceptions from L</uplevel>'d code while the debugger is in use.
+This may be solved in a future version depending on how the core evolves.
+
=head1 DEPENDENCIES
-L<XSLoader> (standard since perl 5.006).
+L<perl> 5.6.1.
+
+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 5.6.0).
=head1 SEE ALSO
=head1 COPYRIGHT & LICENSE
-Copyright 2008,2009,2010,2011 Vincent Pit, all rights reserved.
+Copyright 2008,2009,2010,2011,2012,2013,2014,2015 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.