X-Git-Url: http://git.vpit.fr/?a=blobdiff_plain;f=lib%2FScope%2FUpper.pm;h=104674dae43167fb3afd32fda5f2b9f04a2db6c7;hb=4c8461e81387b2f965156423ae04f418d8da1312;hp=083536422eba2dc3e1dc565041384cdcfff6dae3;hpb=bac4fc46c2d48ce5db75de6c88e0983aeeedf865;p=perl%2Fmodules%2FScope-Upper.git diff --git a/lib/Scope/Upper.pm b/lib/Scope/Upper.pm index 0835364..104674d 100644 --- a/lib/Scope/Upper.pm +++ b/lib/Scope/Upper.pm @@ -9,20 +9,20 @@ Scope::Upper - Act on upper scopes. =head1 VERSION -Version 0.01 +Version 0.08 =cut our $VERSION; BEGIN { - $VERSION = '0.01'; + $VERSION = '0.08'; } =head1 SYNOPSIS package X; - use Scope::Upper qw/reap localize localize_elem/; + use Scope::Upper qw/reap localize localize_elem localize_delete :words/; sub desc { shift->{desc} } @@ -30,37 +30,84 @@ BEGIN { my ($desc) = @_; # First localize $x so that it gets destroyed last - localize '$x' => bless({ desc => $desc }, __PACKAGE__) => 1; + localize '$x' => bless({ desc => $desc }, __PACKAGE__) => UP; # one scope up reap sub { my $pkg = caller; my $x = do { no strict 'refs'; ${$pkg.'::x'} }; # Get the $x in the scope print $x->desc . ": done\n"; - } => 1; + } => SCOPE 1; # same as UP here localize_elem '%SIG', '__WARN__' => sub { my $pkg = caller; my $x = do { no strict 'refs'; ${$pkg.'::x'} }; # Get the $x in the scope CORE::warn($x->desc . ': ' . join('', @_)); - } => 1; + } => UP CALLER 0; # same as UP here + + # delete last @ARGV element + localize_delete '@ARGV', -1 => UP SUB HERE; # same as UP here } package Y; { X::set_tag('pie'); - # $x is now a X object + # $x is now a X object, and @ARGV has one element less warn 'what'; # warns "pie: what at ..." ... } # "pie: done" is printed + package Z; + + use Scope::Upper qw/unwind want_at :words/; + + sub try (&) { + my @result = shift->(); + my $cx = SUB UP SUB; + unwind +(want_at($cx) ? @result : scalar @result) => $cx; + } + + ... + + sub zap { + try { + return @things; # returns to try() and then outside zap() + # not reached + } + # not reached + } + + my @what = zap(); # @what contains @things + =head1 DESCRIPTION -This module lets you defer actions that will take place when the control flow returns into an upper scope. -Currently, you can hook an upper scope end, or localize variables and array/hash values in higher contexts. +This module lets you defer actions I that will take place when the control flow returns into an upper scope. +Currently, you can: + +=over 4 + +=item * + +hook an upper scope end with L ; + +=item * + +localize variables, array/hash values or deletions of elements in higher contexts with respectively L, L and L ; + +=item * + +return values immediately to an upper level with L, and know which context was in use then with L. + +=back =head1 FUNCTIONS +In all those functions, C<$context> refers to the target scope. + +You have to use one or a combination of L to build the C<$context> passed to these functions. +This is needed in order to ensure that the module still works when your program is ran in the debugger. +The only thing you can assume is that it is an I indicator of the frame, which means that you can safely store it at some point and use it when needed, and it will still denote the original scope. + =cut BEGIN { @@ -68,13 +115,13 @@ BEGIN { XSLoader::load(__PACKAGE__, $VERSION); } -=head2 C +=head2 C -Add a destructor that calls C<$callback> when the C<$level>-th upper scope ends, where C<0> corresponds to the current scope. +Add a destructor that calls C<$callback> (in void context) when the upper scope represented by C<$context> ends. -=head2 C +=head2 C -A C delayed to the time of first return into the C<$level>-th upper scope. +A C delayed to the time of first return into the upper scope denoted by C<$context>. C<$what> can be : =over 4 @@ -87,36 +134,191 @@ For example, if C<$value> is a scalar reference, then the C slot of the =item * -A string beginning with a sigil, representing the symbol to localize and assign to. -If the sigil is C<'$'>, then C<$value> isn't dereferenced, that is +A string beginning with a sigil, representing the symbol to localize and to assign to. +If the sigil is C<'$'>, L follows the same syntax as C, i.e. C<$value> isn't dereferenced. +For example, - localize '$x', \'foo' => 0; + localize '$x', \'foo' => HERE; will set C<$x> to a reference to the string C<'foo'>. -Other sigils behave as if a glob was passed. +Other sigils (C<'@'>, C<'%'>, C<'&'> and C<'*'>) require C<$value> to be a reference of the corresponding type. -The symbol is resolved when the actual localization takes place and not when C is called. +When the symbol is given by a string, it is resolved when the actual localization takes place and not when C is called. This means that - sub tag { localize '$x', $_[0] => 1; } + sub tag { localize '$x', $_[0] => UP } will localize in the caller's namespace. =back -=head2 C +=head2 C Similar to L but for array and hash elements. If C<$what> is a glob, the slot to fill is determined from which type of reference C<$value> is ; otherwise it's inferred from the sigil. C<$key> is either an array index or a hash key, depending of which kind of variable you localize. -=head2 C +=head2 C + +Similiar to L, but for deleting variables or array/hash elements. +C<$what> can be: + +=over 4 + +=item * + +A glob, in which case C<$key> is ignored and the call is equivalent to C. + +=item * + +A string beginning with C<'@'> or C<'%'>, for which the call is equivalent to respectiveley C and C. + +=item * + +A string beginning with C<'&'>, which more or less does C in the upper scope. +It's actually more powerful, as C<&func> won't even C anymore. +C<$key> is ignored. + +=back + +=head2 C + +Returns C<@values> I the context pointed by C<$context>, i.e. from the subroutine, eval or format just above C<$context>, and immediately restart the program flow at this point - thus effectively returning to (or from, depending on how you see it) an upper context. + +The upper context isn't coerced onto C<@values>, which is hence always evaluated in list context. +This means that + + my $num = sub { + my @a = ('a' .. 'z'); + unwind @a => HERE; + # not reached + }->(); + +will set C<$num> to C<'z'>. +You can use L to handle these cases. + +=head2 C -Returns the level that currently represents the highest scope. +Like C, but for the subroutine/eval/format just above C<$context>. + +The previous example can then be "corrected" : + + my $num = sub { + my @a = ('a' .. 'z'); + unwind +(want_at(HERE) ? @a : scalar @a) => HERE; + # not reached + }->(); + +will righteously set C<$num> to C<26>. + +=head1 WORDS + +=head2 Constants + +=head3 C + +Returns the context that currently represents the highest scope. + +=head3 C + +The context of the current scope. + +=head2 Getting a context from a context + +For any of those functions, C<$from> is expected to be a context. +When omitted, it defaults to the the current context. + +=head3 C + +The context of the scope just above C<$from>. + +=head3 C + +The context of the closest subroutine above C<$from>. +Note that C<$from> is returned if it is already a subroutine context ; hence C. + +=head3 C + +The context of the closest eval above C<$from>. +Note that C<$from> is returned if it is already an eval context ; hence C. + +=head2 Getting a context from a level + +Here, C<$level> should denote a number of scopes above the current one. +When omitted, it defaults to C<0> and those functions return the same context as L. + +=head3 C + +The C<$level>-th upper context, regardless of its type. + +=head3 C + +The context of the C<$level>-th upper subroutine/eval/format. +It kind of corresponds to the context represented by C, but while e.g. C refers to the caller context, C will refer to the top scope in the current context. + +=head2 Examples + +Where L fires depending on the C<$cxt> : + + sub { + eval { + sub { + { + reap \&cleanup => $cxt; + ... + } # $cxt = SCOPE(0), or HERE + ... + }->(); # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0) + ... + }; # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1) + ... + }->(); # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2) + ... + +Where L, L and L act depending on the C<$cxt> : + + sub { + eval { + sub { + { + localize '$x' => 1 => $cxt; + # $cxt = SCOPE(0), or HERE + ... + } + # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0) + ... + }->(); + # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1) + ... + }; + # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2) + ... + }->(); + # $cxt = SCOPE(4), UP SUB UP SUB, or UP SUB EVAL, or UP CALLER(2), or TOP + ... + +Where L and L point to depending on the C<$cxt>: + + sub { + eval { + sub { + { + unwind @things => $cxt; + ... + } + ... + }->(); # $cxt = SCOPE(0 .. 1), or HERE, or UP, or SUB, or CALLER(0) + ... + }; # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1) + ... + }->(); # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2) + ... =head1 EXPORT -The functions L, L, L and L are only exported on request, either individually or by the tags C<':funcs'> and C<':all'>. +The functions L, L, L, L, L and L are only exported on request, either individually or by the tags C<':funcs'> and C<':all'>. + +Same goes for the words L, L, L, L, L, L and L that are only exported on request, individually or by the tags C<':words'> and C<':all'>. =cut @@ -124,11 +326,41 @@ use base qw/Exporter/; our @EXPORT = (); our %EXPORT_TAGS = ( - funcs => [ qw/reap localize localize_elem TOPLEVEL/ ], + funcs => [ qw/reap localize localize_elem localize_delete unwind want_at/ ], + words => [ qw/TOP HERE UP SUB EVAL SCOPE CALLER/ ], ); our @EXPORT_OK = map { @$_ } values %EXPORT_TAGS; $EXPORT_TAGS{'all'} = [ @EXPORT_OK ]; +=head1 CAVEATS + +Be careful that local variables are restored in the reverse order in which they were localized. +Consider those examples: + + local $x = 0; + { + reap sub { print $x } => HERE; + local $x = 1; + ... + } + # prints '0' + ... + { + local $x = 1; + reap sub { $x = 2 } => HERE; + ... + } + # $x is 0 + +The first case is "solved" by moving the C before the C, and the second by using L instead of L. + +The effects of L, L and L can't cross C blocks, hence calling those functions in C is deemed to be useless. +This is an hopeless case because C blocks are executed once while localizing constructs should do their job at each run. +However, it's possible to hook the end of the current scope compilation with L. + +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. + =head1 DEPENDENCIES L (standard since perl 5.006). @@ -153,13 +385,17 @@ You can find documentation for this module with the perldoc command. perldoc Scope::Upper +Tests code coverage report is available at L. + =head1 ACKNOWLEDGEMENTS Inspired by Ricardo Signes. +Thanks to Shawn M. Moore for motivation. + =head1 COPYRIGHT & LICENSE -Copyright 2008 Vincent Pit, all rights reserved. +Copyright 2008-2009 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.