This is 0.06

[perl/modules/Scope-Upper.git] / README

diff --git a/README b/README
index 5e2fb7e35e9345a478ab473f5744fd83ab65b279..8dd7b5d74759860924adbc5b5fa70414af196113 100644 (file)
--- a/README
+++ b/README
@@ -2,12 +2,12 @@ NAME
     Scope::Upper - Act on upper scopes.
 
 VERSION
     Scope::Upper - Act on upper scopes.
 
 VERSION

-    Version 0.02
+    Version 0.06

 
 SYNOPSIS
         package X;
 
 
 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} }
 
 
         sub desc { shift->{desc} }
 


@@ -15,43 +15,79 @@ SYNOPSIS
          my ($desc) = @_;
 
          # First localize $x so that it gets destroyed last
          my ($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";
 
          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('', @_));
 
          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');
         }
 
         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
 
          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()
+         }
+        }
+
+        my @what = zap(); # @what contains @things
+

 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
 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.
+    end, or localize variables, array/hash values or deletions of elements
+    in higher contexts. You can also return to an upper level and know which
+    context was in use then.

 
 FUNCTIONS
 
 FUNCTIONS

-  "reap $callback, $level"
-    Add a destructor that calls $callback when the $level-th upper scope
-    ends, where 0 corresponds to the current scope.
+    In all those functions, $context refers to the target scope.
+
+    You have to use one or a combination of "WORDS" to build the $context to
+    pass to these functions. This is needed in order to ensure that the
+    module still works when your program is ran in the debugger. Don't try
+    to use a raw value or things will get messy.
+
+    The only thing you can assume is that it is an *absolute* indicator of
+    the frame. This means that you can safely store it at some point and use
+    it when needed, and it will still denote the original scope.

 
 

-  "localize $what, $value, $level"
-    A "local" delayed to the time of first return into the $level-th upper
-    scope. $what can be :
+  "reap $callback, $context"
+    Add a destructor that calls $callback 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 :

 
     *   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
 
     *   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


@@ -64,7 +100,7 @@ FUNCTIONS
         syntax as "local $x = $value", i.e. $value isn't dereferenced. For
         example,
 
         syntax as "local $x = $value", i.e. $value isn't dereferenced. For
         example,
 

-            localize '$x', \'foo' => 0;
+            localize '$x', \'foo' => HERE;

 
         will set $x to a reference to the string 'foo'. Other sigils ('@',
         '%', '&' and '*') require $value to be a reference of the
 
         will set $x to a reference to the string 'foo'. Other sigils ('@',
         '%', '&' and '*') require $value to be a reference of the


@@ -74,23 +110,101 @@ FUNCTIONS
         localization takes place and not when "localize" is called. This
         means that
 
         localization takes place and not when "localize" is called. This
         means that
 

-            sub tag { localize '$x', $_[0] => 1; }
+            sub tag { localize '$x', $_[0] => UP }

 
         will localize in the caller's namespace.
 
 
         will localize in the caller's namespace.
 

-  "localize_elem $what, $key, $value, $level"
+  "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.
 
     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.
 

-  "TOPLEVEL"
-    Returns the level that currently represents the highest scope.
+  "localize_delete $what, $key, $context"
+    Similiar to "localize", but for deleting variables or array/hash
+    elements. $what can be:
+
+    *   A glob, in which case $key is ignored and the call is equivalent to
+        "local *x".
+
+    *   A string beginning with '@' or '%', for which the call is equivalent
+        to respectiveley "local $a[$key]; delete $a[$key]" and "local
+        $h{$key}; delete $h{$key}".
+
+    *   A string beginning with '&', which more or less does "undef &func"
+        in the upper scope. It's actually more powerful, as &func won't even
+        "exists" anymore. $key is ignored.
+
+  "unwind @values, $context"
+    Returns @values *from* the context pointed by $context, i.e. from the
+    subroutine, eval or format just above $context.
+
+    The upper context isn't coerced onto @values, which is hence always
+    evaluated in list context. This means that
+
+        my $num = sub {
+         my @a = ('a' .. 'z');
+         unwind @a => HERE;
+        }->();
+
+    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
+    $context.
+
+    The previous example can then be "corrected" :
+
+        my $num = sub {
+         my @a = ('a' .. 'z');
+         unwind +(want_at(HERE) ? @a : scalar @a) => HERE;
+        }->();
+
+    will righteously set $num to 26.
+
+WORDS
+  Constants
+   "TOP"
+    Returns the context that currently represents the highest scope.
+
+   "HERE"
+    The context of the current scope.
+
+  Getting a context from a context
+    For any of those functions, $from is expected to be a context. When
+    omitted, it defaults to the the current context.
+
+   "UP $from"
+    The context of the scope just above $from.
+
+   "SUB $from"
+    The context of the closest subroutine above $from.
+
+   "EVAL $from"
+    The context of the closest eval above $from.
+
+  Getting a context from a level
+    Here, $level should denote a number of scopes above the current one.
+    When omitted, it defaults to 0 and those functions return the same
+    context as "HERE".
+
+   "SCOPE $level"
+    The $level-th upper context, regardless of its type.
+
+   "CALLER $level"
+    The context of the $level-th upper subroutine/eval/format. It kind of
+    corresponds to the context represented by "caller $level", but while
+    e.g. "caller 0" refers to the caller context, "CALLER 0" will refer to
+    the top scope in the current context.

 
 EXPORT
 
 EXPORT

-    The functions "reap", "localize", "localize_elem" and "TOPLEVEL" are
-    only exported on request, either individually or by the tags ':funcs'
-    and ':all'.
+    The functions "reap", "localize", "localize_elem", "localize_delete",
+    "unwind" and "want_at" are only exported on request, either individually
+    or by the tags ':funcs' 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'.

 
 CAVEATS
     Be careful that local variables are restored in the reverse order in
 
 CAVEATS
     Be careful that local variables are restored in the reverse order in


@@ -98,7 +212,7 @@ CAVEATS
 
         local $x = 0;
         {
 
         local $x = 0;
         {

-         reap sub { print $x } => 0;
+         reap sub { print $x } => HERE;

          local $x = 1;
          ...
         }
          local $x = 1;
          ...
         }


@@ -106,7 +220,7 @@ CAVEATS
         ...
         {
          local $x = 1;
         ...
         {
          local $x = 1;

-         reap sub { $x = 2 } => 0;
+         reap sub { $x = 2 } => HERE;

          ...
         }
         # $x is 0
          ...
         }
         # $x is 0


@@ -119,6 +233,10 @@ CAVEATS
     useless. This is an hopeless case because "BEGIN" blocks are executed
     once while localizing constructs should do their job at each run.
 
     useless. This is an hopeless case because "BEGIN" blocks are executed
     once while localizing constructs should do their job at each run.
 

+    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 fixes.
+

 DEPENDENCIES
     XSLoader (standard since perl 5.006).
 
 DEPENDENCIES
     XSLoader (standard since perl 5.006).
 


@@ -148,8 +266,10 @@ SUPPORT
 ACKNOWLEDGEMENTS
     Inspired by Ricardo Signes.
 
 ACKNOWLEDGEMENTS
     Inspired by Ricardo Signes.
 

+    Thanks to Shawn M. Moore for motivation.
+

 COPYRIGHT & LICENSE
 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.
 
     This program is free software; you can redistribute it and/or modify it
     under the same terms as Perl itself.