In perl.git, the branch deletelocal has been updated <http://perl5.git.perl.org/perl.git/commitdiff/d361fafa2ec7914fdb219a034554936dd4d6cdc7?hp=7332a6c406299d5e73836d2410689bd7c3ae4782>
- Log ----------------------------------------------------------------- commit d361fafa2ec7914fdb219a034554936dd4d6cdc7 Author: Vincent Pit <[email protected]> Date: Mon Jul 27 16:13:33 2009 +0200 Document "delete local" in perlsub ----------------------------------------------------------------------- Summary of changes: pod/perlfunc.pod | 8 ++++++++ pod/perlsub.pod | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 58 insertions(+), 0 deletions(-) diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod index 23e5535..3a345aa 100644 --- a/pod/perlfunc.pod +++ b/pod/perlfunc.pod @@ -1234,6 +1234,10 @@ lookup: delete $ref->[$x][$y][$index]; delete @{$ref->[$x][$y]}[$index1, $index2, @moreindices]; +The C<delete local EXPR> construct can also be used to localize the deletion +of array/hash elements to the current block. +See L<perlsub/"Localized deletion of elements of composite types">. + =item die LIST X<die> X<throw> X<exception> X<raise> X<$@> X<abort> @@ -2736,6 +2740,10 @@ block, file, or eval. If more than one value is listed, the list must be placed in parentheses. See L<perlsub/"Temporary Values via local()"> for details, including issues with tied arrays and hashes. +The C<delete local EXPR> construct can also be used to localize the deletion +of array/hash elements to the current block. +See L<perlsub/"Localized deletion of elements of composite types">. + =item localtime EXPR X<localtime> X<ctime> diff --git a/pod/perlsub.pod b/pod/perlsub.pod index 74d0b1a..325c823 100644 --- a/pod/perlsub.pod +++ b/pod/perlsub.pod @@ -535,6 +535,7 @@ Synopsis: local @oof = @bar; # make @oof dynamic, and init it local $hash{key} = "val"; # sets a local value for this hash entry + delete local $hash{key}; # delete this entry for the current block local ($cond ? $v1 : $v2); # several types of lvalues support # localization @@ -692,6 +693,55 @@ Perl will print The behavior of local() on non-existent members of composite types is subject to change in future. +=head3 Localized deletion of elements of composite types +X<delete> X<local, composite type element> X<local, array element> X<local, hash element> + +You can use the C<delete local $array[$idx]> and C<delete local $hash{key}> +constructs to delete a composite type entry for the current block and restore +it when it ends. They return the array/hash value before the localization, +which means that they are respectively equivalent to + + do { + my $val = $array[$idx]; + local $array[$idx]; + delete $array[$idx]; + $val + } + +and + + do { + my $val = $hash{key}; + local $hash{key}; + delete $hash{key}; + $val + } + +except that for those the C<local> is scoped to the C<do> block. Slices are +also accepted. + + my %hash = ( + a => [ 7, 8, 9 ], + b => 1, + ) + + { + my $a = delete local $hash{a}; + # $a is [ 7, 8, 9 ] + # %hash is (b => 1) + + { + my @nums = delete local @$a[0, 2] + # @nums is (7, 9) + # $a is [ undef, 8 ] + + $a[0] = 999; # will be erased when the scope ends + } + # $a is back to [ 7, 8, 9 ] + + } + # %hash is back to its original state + =head2 Lvalue subroutines X<lvalue> X<subroutine, lvalue> -- Perl5 Master Repository
