X-Git-Url: http://git.vpit.fr/?a=blobdiff_plain;f=README;h=527b31b15d7386a6de85a95a87825fccb16ccdf8;hb=fe6605581cbe68b5935e72c98a8a685379d1f320;hp=16f88ca56cd9895c60ad6903efac19530457fa7e;hpb=da4cceb83810de827ceba611a1459c0afd672039;p=perl%2Fmodules%2FScope-Upper.git diff --git a/README b/README index 16f88ca..527b31b 100644 --- a/README +++ b/README @@ -2,53 +2,81 @@ NAME Scope::Upper - Act on upper scopes. VERSION - Version 0.07 + Version 0.12 SYNOPSIS - package X; + "reap", "localize", "localize_elem", "localize_delete" and "WORDS" : + + package Scope; use Scope::Upper qw/reap localize localize_elem localize_delete :words/; - sub desc { shift->{desc} } + sub new { + my ($class, $name) = @_; + + localize '$tag' => bless({ name => $name }, $class) => UP; - sub set_tag { - my ($desc) = @_; + reap { print Scope->tag->name, ": end\n" } UP; + } - # First localize $x so that it gets destroyed last - localize '$x' => bless({ desc => $desc }, __PACKAGE__) => UP; # one scope up + # Get the tag stored in the caller namespace + sub tag { + my $l = 0; + my $pkg = __PACKAGE__; + $pkg = caller $l++ while $pkg eq __PACKAGE__; - reap sub { - my $pkg = caller; - my $x = do { no strict 'refs'; ${$pkg.'::x'} }; # Get the $x in the scope - print $x->desc . ": done\n"; - } => SCOPE 1; # same as UP here + no strict 'refs'; + ${$pkg . '::tag'}; + } + sub name { shift->{name} } + + # Locally capture warnings and reprint them with the name prefixed + sub catch { 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('', @_)); - } => UP CALLER 0; # same as UP here + print Scope->tag->name, ': ', @_; + } => UP; + } - # delete last @ARGV element - localize_delete '@ARGV', -1 => UP SUB HERE; # same as UP here + # Locally clear @INC + sub private { + for (reverse 0 .. $#INC) { + # First UP is the for loop, second is the sub boundary + localize_delete '@INC', $_ => UP UP; + } } - package Y; + ... + + package UserLand; { - X::set_tag('pie'); - # $x is now a X object, and @ARGV has one element less - warn 'what'; # warns "pie: what at ..." - ... - } # "pie: done" is printed + Scope->new("top"); # initializes $UserLand::tag - package Z; + { + Scope->catch; + 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..." + } + + require Cwd; # loads Cwd.pm + } + + } # prints "top: done" + + "unwind" and "want_at" : + + package Try; use Scope::Upper qw/unwind want_at :words/; sub try (&) { my @result = shift->(); - my $cx = SUB UP SUB; + my $cx = SUB UP; # Point to the sub above this one unwind +(want_at($cx) ? @result : scalar @result) => $cx; } @@ -56,11 +84,15 @@ SYNOPSIS sub zap { try { + my @things = qw/a b c/; return @things; # returns to try() and then outside zap() - } + # not reached + }; + # not reached } - my @what = zap(); # @what contains @things + my @stuff = zap(); # @stuff contains qw/a b c/ + my $stuff = zap(); # $stuff contains 3 DESCRIPTION This module lets you defer actions *at run-time* that will take place @@ -86,12 +118,12 @@ FUNCTIONS needed, and it will still denote the original scope. "reap $callback, $context" - Add a destructor that calls $callback when the upper scope represented - by $context ends. + Adds a destructor that calls $callback (in void context) when the upper + scope represented by $context ends. "localize $what, $value, $context" - A "local" delayed to the time of first return into the upper scope - denoted by $context. $what can be : + Introduces a "local" delayed to the time of first return into the upper + scope denoted by $context. $what can be : * A glob, in which case $value can either be a glob or a reference. "localize" follows then the same syntax as "local *x = $value". For @@ -111,22 +143,54 @@ FUNCTIONS corresponding type. When the symbol is given by a string, it is resolved when the actual - localization takes place and not when "localize" is called. This - means that - - sub tag { localize '$x', $_[0] => UP } - - will localize in the caller's namespace. + localization takes place and not when "localize" is called. Thus, if + the symbol name is not qualified, it will refer to the variable in + the package where the localization actually takes place and not in + the one where the "localize" call was compiled. For example, + + { + package Scope; + sub new { localize '$tag', $_[0] => UP } + } + + { + package Tool; + { + Scope->new; + ... + } + } + + will localize $Tool::tag and not $Scope::tag. If you want the other + behaviour, you just have to specify $what as a glob or a qualified + name. + + Note that if $what is a string denoting a variable that wasn't + declared beforehand, the relevant slot will be vivified as needed + and won't be deleted from the glob when the localization ends. This + situation never arises with "local" because it only compiles when + the localized variable is already declared. Although I believe it + shouldn't be a problem as glob slots definedness is pretty much an + implementation detail, this behaviour may change in the future if + proved harmful. "localize_elem $what, $key, $value, $context" - Similar to "localize" but for array and hash elements. If $what is a - glob, the slot to fill is determined from which type of reference $value - is ; otherwise it's inferred from the sigil. $key is either an array - index or a hash key, depending of which kind of variable you localize. + Introduces a "local $what[$key] = $value" or "local $what{$key} = + $value" delayed to the time of first return into the upper scope denoted + by $context. Unlike "localize", $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, "localize_elem" will throw + an exception. $key is either an array index or a hash key, depending of + which kind of variable you localize. + + If $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. "localize_delete $what, $key, $context" - Similiar to "localize", but for deleting variables or array/hash - elements. $what can be: + Introduces the deletion of a variable or an array/hash element delayed + to the time of first return into the upper scope denoted by $context. + $what can be: * A glob, in which case $key is ignored and the call is equivalent to "local *x". @@ -141,9 +205,9 @@ FUNCTIONS "unwind @values, $context" Returns @values *from* the context pointed by $context, i.e. from the - subroutine, eval or format just above $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. + subroutine, eval or format at or just above $context, and immediately + restart the program flow at this point - thus effectively returning to + an upper scope. The upper context isn't coerced onto @values, which is hence always evaluated in list context. This means that @@ -151,12 +215,13 @@ FUNCTIONS my $num = sub { my @a = ('a' .. 'z'); unwind @a => HERE; + # not reached }->(); will set $num to 'z'. You can use "want_at" to handle these cases. "want_at $context" - Like "wantarray", but for the subroutine/eval/format just above + Like "wantarray", but for the subroutine/eval/format at or just above $context. The previous example can then be "corrected" : @@ -164,9 +229,14 @@ FUNCTIONS my $num = sub { my @a = ('a' .. 'z'); unwind +(want_at(HERE) ? @a : scalar @a) => HERE; + # not reached }->(); - will righteously set $num to 26. + will rightfully set $num to 26. + +CONSTANTS + "SU_THREADSAFE" + True iff the module could have been built when thread-safety features. WORDS Constants @@ -268,6 +338,9 @@ EXPORT "unwind" and "want_at" are only exported on request, either individually or by the tags ':funcs' and ':all'. + The constant "SU_THREADSAFE" is also only exported on request, + individually or by the tags ':consts' and ':all'. + Same goes for the words "TOP", "HERE", "UP", "SUB", "EVAL", "SCOPE" and "CALLER" that are only exported on request, individually or by the tags ':words' and ':all'. @@ -309,8 +382,17 @@ DEPENDENCIES XSLoader (standard since perl 5.006). SEE ALSO + "local" in perlfunc, "Temporary Values via local()" in perlsub. + Alias, Hook::Scope, Scope::Guard, Guard. + Continuation::Escape is a thin wrapper around Scope::Upper that gives + you a continuation passing style interface to "unwind". It's easier to + use, but it requires you to have control over the scope where you want + to return. + + Scope::Escape. + AUTHOR Vincent Pit, "", . @@ -337,7 +419,7 @@ ACKNOWLEDGEMENTS Thanks to Shawn M. Moore for motivation. COPYRIGHT & LICENSE - Copyright 2008-2009 Vincent Pit, all rights reserved. + Copyright 2008,2009,2010 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.