+will rightfully set C<$num> to C<26>.
+
+=head2 C<context_info>
+
+ my ($package, $filename, $line, $subroutine, $hasargs,
+ $wantarray, $evaltext, $is_require, $hints, $bitmask,
+ $hinthash) = context_info $context;
+
+Gives information about the context denoted by C<$context>, akin to what L<perlfunc/caller> provides but not limited only to subroutine, eval and format contexts.
+When C<$context> is omitted, it defaults to the current context.
+
+The returned values are, in order :
+
+=over 4
+
+=item *
+
+I<(index 0)> : the namespace in use when the context was created ;
+
+=item *
+
+I<(index 1)> : the name of the file at the point where the context was created ;
+
+=item *
+
+I<(index 2)> : the line number at the point where the context was created ;
+
+=item *
+
+I<(index 3)> : the name of the subroutine called for this context, or C<undef> if this is not a subroutine context ;
+
+=item *
+
+I<(index 4)> : a boolean indicating whether a new instance of C<@_> was set up for this context, or C<undef> if this is not a subroutine context ;
+
+=item *
+
+I<(index 5)> : the context (in the sense of L<perlfunc/wantarray>) in which the context (in our sense) is executed ;
+
+=item *
+
+I<(index 6)> : the contents of the string being compiled for this context, or C<undef> if this is not an eval context ;
+
+=item *
+
+I<(index 7)> : a boolean indicating whether this eval context was created by C<require>, or C<undef> if this is not an eval context ;
+
+=item *
+
+I<(index 8)> : the value of the lexical hints in use when the context was created ;
+
+=item *
+
+I<(index 9)> : a bit string representing the warnings in use when the context was created ;
+
+=item *
+
+I<(index 10)> : a reference to the lexical hints hash in use when the context was created (only on perl 5.10 or greater).
+
+=back
+
+=head2 C<uplevel>
+
+ my @ret = uplevel { ...; return @ret };
+ my @ret = uplevel { my @args = @_; ...; return @ret } @args, $context;
+ my @ret = &uplevel($callback, @args, $context);
+
+Executes the code reference C<$callback> with arguments C<@args> as if it were located at the subroutine stack frame pointed by C<$context>, effectively fooling C<caller> and C<die> into believing that the call actually happened higher in the stack.
+The code is executed in the context of the C<uplevel> call, and what it returns is returned as-is by C<uplevel>.
+
+ sub target {
+ faker(@_);
+ }
+
+ sub faker {
+ uplevel {
+ map { 1 / $_ } @_;
+ } @_ => CALLER(1);
+ }
+
+ my @inverses = target(1, 2, 4); # @inverses contains (0, 0.5, 0.25)
+ my $count = target(1, 2, 4); # $count is 3
+
+Note that if C<@args> is empty, then the C<$context> parameter is optional and defaults to the current context ; otherwise it is mandatory.
+
+L<Sub::Uplevel> also implements a pure-Perl version of C<uplevel>.
+Both are identical, with the following caveats :
+
+=over 4
+
+=item *
+
+The L<Sub::Uplevel> implementation of C<uplevel> may execute a code reference in the context of B<any> upper stack frame.
+The L<Scope::Upper> version can only uplevel to a B<subroutine> stack frame, and will croak if you try to target an C<eval> or a format.
+
+=item *
+
+Exceptions thrown from the code called by this version of C<uplevel> will not be caught by C<eval> blocks between the target frame and the uplevel call, while they will for L<Sub::Uplevel>'s version.
+This means that :
+
+ eval {
+ sub {
+ local $@;
+ eval {
+ sub {
+ uplevel { die 'wut' } CALLER(2); # for Scope::Upper
+ # uplevel(3, sub { die 'wut' }) # for Sub::Uplevel
+ }->();
+ };
+ print "inner block: $@";
+ $@ and exit;
+ }->();
+ };
+ print "outer block: $@";
+
+will print "inner block: wut..." with L<Sub::Uplevel> and "outer block: wut..." with L<Scope::Upper>.
+
+=item *
+
+L<Sub::Uplevel> globally overrides the Perl keyword C<caller>, while L<Scope::Upper> does not.
+
+=back
+
+A simple wrapper lets you mimic the interface of L<Sub::Uplevel/uplevel> :
+
+ use Scope::Upper;
+
+ sub uplevel {
+ my $frame = shift;
+ my $code = shift;
+ my $cxt = Scope::Upper::CALLER($frame);
+ &Scope::Upper::uplevel($code => @_ => $cxt);
+ }
+
+Albeit the three exceptions listed above, it passes all the tests of L<Sub::Uplevel>.
+
+=head2 C<uid>
+
+ my $uid = uid;
+ my $uid = uid $context;
+
+Returns an unique identifier (UID) for the context (or dynamic scope) pointed by C<$context>, or for the current context if C<$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 C<eq> operator to compare them.
+
+To check whether a given UID is valid, you can use the L</validate_uid> function.
+
+=head2 C<validate_uid>
+
+ my $is_valid = validate_uid $uid;
+
+Returns true if and only if C<$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
+ ...
+ }
+
+=head1 CONSTANTS
+
+=head2 C<SU_THREADSAFE>
+
+True iff the module could have been built when thread-safety features.
projects / perl / modules / Scope-Upper.git / blobdiff