This is 0.11

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

diff --git a/README b/README
index 074581cbe7cf8130d2d391cbbc85974e775d7b8f..40d7734d222ec14c002f1266db88df263979809b 100644 (file)
--- a/README
+++ b/README
@@ -2,53 +2,81 @@ NAME
     Scope::Upper - Act on upper scopes.
 
 VERSION
     Scope::Upper - Act on upper scopes.
 
 VERSION

-    Version 0.10
+    Version 0.11

 
 SYNOPSIS
 
 SYNOPSIS

-        package X;
+    "reap", "localize", "localize_elem", "localize_delete" and "WORDS" :
+
+        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 desc { shift->{desc} }
+        sub new {
+         my ($class, $name) = @_;
+
+         localize '$tag' => bless({ name => $name }, $class) => UP;
+
+         reap { print Scope->tag->name, ": end\n" } UP;
+        }

 
 

-        sub set_tag {
-         my ($desc) = @_;
+        # Get the tag stored in the caller namespace
+        sub tag {
+         my $l   = 0;
+         my $pkg = __PACKAGE__;
+         $pkg    = caller $l++ while $pkg eq __PACKAGE__;

 
 

-         # First localize $x so that it gets destroyed last
-         localize '$x' => bless({ desc => $desc }, __PACKAGE__) => UP; # one scope up
+         no strict 'refs';
+         ${$pkg . '::tag'};
+        }

 
 

-         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
+        sub name { shift->{name} }

 
 

+        # Locally capture warnings and reprint them with the name prefixed
+        sub catch {

          localize_elem '%SIG', '__WARN__' => sub {
          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
+
+         {
+          Scope->catch;
+          my $one = 1 + undef;   # prints "top: Use of uninitialized value..."

 
 

-        package Z;
+          {
+           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->();
 
         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;
         }
 
          unwind +(want_at($cx) ? @result : scalar @result) => $cx;
         }
 


@@ -56,13 +84,15 @@ SYNOPSIS
 
         sub zap {
          try {
 
         sub zap {
          try {

+          my @things = qw/a b c/;

           return @things; # returns to try() and then outside zap()
           # not reached
           return @things; # returns to try() and then outside zap()
           # not reached

-         }
+         };

          # 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
 
 DESCRIPTION
     This module lets you defer actions *at run-time* that will take place


@@ -88,12 +118,12 @@ FUNCTIONS
     needed, and it will still denote the original scope.
 
   "reap $callback, $context"
     needed, and it will still denote the original scope.
 
   "reap $callback, $context"

-    Add a destructor that calls $callback (in void context) when the upper
+    Adds a destructor that calls $callback (in void context) when the upper

     scope represented by $context ends.
 
   "localize $what, $value, $context"
     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
 
     *   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


@@ -113,22 +143,54 @@ FUNCTIONS
         corresponding type.
 
         When the symbol is given by a string, it is resolved when the actual
         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"
 
   "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"
 
   "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".
 
     *   A glob, in which case $key is ignored and the call is equivalent to
         "local *x".


@@ -143,9 +205,9 @@ FUNCTIONS
 
   "unwind @values, $context"
     Returns @values *from* the context pointed by $context, i.e. from the
 
   "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
 
     The upper context isn't coerced onto @values, which is hence always
     evaluated in list context. This means that


@@ -159,7 +221,7 @@ FUNCTIONS
     will set $num to 'z'. You can use "want_at" to handle these cases.
 
   "want_at $context"
     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" :
     $context.
 
     The previous example can then be "corrected" :


@@ -320,6 +382,8 @@ DEPENDENCIES
     XSLoader (standard since perl 5.006).
 
 SEE ALSO
     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
     Alias, Hook::Scope, Scope::Guard, Guard.
 
     Continuation::Escape is a thin wrapper around Scope::Upper that gives


@@ -327,6 +391,8 @@ SEE ALSO
     use, but it requires you to have control over the scope where you want
     to return.
 
     use, but it requires you to have control over the scope where you want
     to return.
 

+    Scope::Escape.
+

 AUTHOR
     Vincent Pit, "<perl at profvince.com>", <http://www.profvince.com>.
 
 AUTHOR
     Vincent Pit, "<perl at profvince.com>", <http://www.profvince.com>.