Scope::Upper - Act on upper scopes.
VERSION
- Version 0.17
+ Version 0.18
SYNOPSIS
"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 new {
my ($class, $name) = @_;
package UserLand;
{
- Scope->new("top"); # initializes $UserLand::tag
+ Scope->new("top"); # initializes $UserLand::tag
{
Scope->catch;
- my $one = 1 + undef; # prints "top: Use of uninitialized value..."
+ 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..."
- }
+ print $@; # prints "Can't locate Cwd.pm in @INC
+ } # (@INC contains:) at..."
- require Cwd; # loads Cwd.pm
+ require Cwd; # loads Cwd.pm
}
- } # prints "top: done"
+ } # prints "top: done"
"unwind" and "want_at" :
target('hello'); # "hello from Uplevel::target()"
+ "uid" and "validate_uid" :
+
+ use Scope::Upper qw<uid validate_uid>;
+
+ my $uid;
+
+ {
+ $uid = uid();
+ {
+ if ($uid eq uid(UP)) { # yes
+ ...
+ }
+ if (validate_uid($uid)) { # yes
+ ...
+ }
+ }
+ }
+
+ if (validate_uid($uid)) { # no
+ ...
+ }
+
DESCRIPTION
This module lets you defer actions *at run-time* that will take place
when the control flow returns into an upper scope. Currently, you can:
which context was in use then with "want_at" ;
* execute a subroutine in the setting of an upper subroutine stack
- frame with "uplevel".
+ frame with "uplevel" ;
+
+ * uniquely identify contextes with "uid" and "validate_uid".
FUNCTIONS
In all those functions, $context refers to the target scope.
Albeit the three exceptions listed above, it passes all the tests of
Sub::Uplevel.
+ "uid $context"
+ Returns an unique identifier (UID) for the context (or dynamic scope)
+ pointed by $context, or for the current context if $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.
+
+ my $uid;
+
+ {
+ $uid = uid;
+ if ($uid eq uid()) { # yes, this is the same context
+ ...
+ }
+ {
+ if ($uid eq uid()) { # no, we are one scope below
+ ...
+ }
+ if ($uid eq uid(UP)) { # yes, UP points to the same scope as $uid
+ ...
+ }
+ }
+ }
+
+ # $uid is now invalid
+
+ {
+ if ($uid eq uid()) { # no, this is another block
+ ...
+ }
+ }
+
+ For example, each loop iteration gets its own UID :
+
+ my %uids;
+
+ for (1 .. 5) {
+ my $uid = uid;
+ $uids{$uid} = $_;
+ }
+
+ # %uids has 5 entries
+
+ The UIDs are not guaranteed to be numbers, so you must use the "eq"
+ operator to compare them.
+
+ To check whether a given UID is valid, you can use the "validate_uid"
+ function.
+
+ "validate_uid $uid"
+ Returns true if and only if $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).
+
+ my $uid;
+
+ {
+ $uid = uid();
+ if (validate_uid($uid)) { # yes
+ ...
+ }
+ {
+ if (validate_uid($uid)) { # yes
+ ...
+ }
+ }
+ }
+
+ if (validate_uid($uid)) { # no
+ ...
+ }
+
CONSTANTS
"SU_THREADSAFE"
True iff the module could have been built when thread-safety features.
{
reap \&cleanup => $cxt;
...
- } # $cxt = SCOPE(0), or HERE
+ } # $cxt = SCOPE(0) = HERE
...
- }->(); # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0)
+ }->(); # $cxt = SCOPE(1) = UP = SUB = CALLER(0)
...
- }; # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1)
+ }; # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1)
...
- }->(); # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2)
+ }->(); # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2)
...
Where "localize", "localize_elem" and "localize_delete" act depending on
sub {
{
localize '$x' => 1 => $cxt;
- # $cxt = SCOPE(0), or HERE
+ # $cxt = SCOPE(0) = HERE
...
}
- # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0)
+ # $cxt = SCOPE(1) = UP = SUB = CALLER(0)
...
}->();
- # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1)
+ # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1)
...
};
- # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2)
+ # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2)
...
}->();
- # $cxt = SCOPE(4), UP SUB UP SUB, or UP SUB EVAL, or UP CALLER(2), or TOP
+ # $cxt = SCOPE(4), UP SUB UP SUB = UP SUB EVAL = UP CALLER(2) = TOP
...
Where "unwind", "want_at" and "uplevel" point to depending on the $cxt:
eval {
sub {
{
- unwind @things => $cxt; # or uplevel { ... } $cxt;
+ unwind @things => $cxt; # or uplevel { ... } $cxt;
...
}
...
- }->(); # $cxt = SCOPE(0 .. 1), or HERE, or UP, or SUB, or CALLER(0)
+ }->(); # $cxt = SCOPE(0) = SCOPE(1) = HERE = UP = SUB = CALLER(0)
...
- }; # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1) (*)
+ }; # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1) (*)
...
- }->(); # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2)
+ }->(); # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2)
...
# (*) Note that uplevel() will croak if you pass that scope frame,
may help to use a perl higher than 5.8.9 or 5.10.0, as they contain some
context-related fixes.
- Calling "goto" to replace an "uplevel"'d code frame does not work when a
- custom runloop is used or when debugging flags are set with "perl -D".
- In those two cases, "uplevel" will look for a "goto &sub" statement in
+ Calling "goto" to replace an "uplevel"'d code frame does not work :
+
+ * for a "perl" older than the 5.8 series ;
+
+ * for a "DEBUGGING" "perl" run with debugging flags set (as in "perl
+ -D ...") ;
+
+ * when the runloop callback is replaced by another module.
+
+ In those three cases, "uplevel" will look for a "goto &sub" statement in
its callback and, if there is one, throw an exception before executing
the code.
projects / perl / modules / Scope-Upper.git / commitdiff