package feature;
-our $VERSION = '1.00';
+our $VERSION = '1.10';
# (feature name) => (internal name, used in %^H)
my %feature = (
switch => 'feature_switch',
- "~~" => "feature_~~",
say => "feature_say",
err => "feature_err",
+ state => "feature_state",
);
my %feature_bundle = (
- "5.10" => [qw(switch ~~ say err)],
+ "5.10.0" => [qw(switch say err state)],
);
+# latest version here
+# keep it harcoded until we actually bump the version number to 5.10
+$feature_bundle{"5.10"} = $feature_bundle{"5.10.0"};
+#$feature_bundle{"5.10"} = $feature_bundle{sprintf("%vd",$^V)};
-
-# Here are some notes that probably shouldn't be in the public
-# documentation, but which it's useful to have somewhere.
-#
-# One side-effect of the change is that C<prototype("CORE::continue")>
-# no longer throws the error C<Can't find an opnumber for "continue">.
-# One of the tests in t/op/cproto.t had to be changed to accommodate
-# this, but it really shouldn't affect real-world code.
-#
# TODO:
-# - sort out the smartmatch semantics
-# - think about versioned features (use switch => 2)
-#
-# -- Robin 2005-12
+# - think about versioned features (use feature switch => 2)
=head1 NAME
and will be parsed only when the appropriate feature pragma is in
scope.
-=head2 The 'switch' feature
+=head2 Lexical effect
-C<use feature 'switch'> tells the compiler to enable the Perl 6
-given/when construct from here to the end of the enclosing BLOCK.
+Like other pragmas (C<use strict>, for example), features have a lexical
+effect. C<use feature qw(foo)> will only make the feature "foo" available
+from that point to the end of the enclosing block.
-See L<perlsyn/"Switch statements"> for details.
+ {
+ use feature 'say';
+ say "say is available here";
+ }
+ print "But not here.\n";
+
+=head2 C<no feature>
-=head2 The '~~' feature
+Features can also be turned off by using C<no feature "foo">. This too
+has lexical effect.
-C<use feature '~~'> tells the compiler to enable the Perl 6
-smart match C<~~> operator from here to the end of the enclosing BLOCK.
+ use feature 'say';
+ say "say is available here";
+ {
+ no feature 'say';
+ print "But not here.\n";
+ }
+ say "Yet it is here.";
+
+C<no feature> with no features specified will turn off all features.
+
+=head2 The 'switch' feature
-See L<perlsyn/"Smart Matching in Detail"> for details.
+C<use feature 'switch'> tells the compiler to enable the Perl 6
+given/when construct.
+
+See L<perlsyn/"Switch statements"> for details.
=head2 The 'say' feature
C<use feature 'say'> tells the compiler to enable the Perl 6
-C<say> function from here to the end of the enclosing BLOCK.
+C<say> function.
See L<perlfunc/say> for details.
=head2 the 'err' feature
C<use feature 'err'> tells the compiler to enable the C<err>
-operator from here to the end of the enclosing BLOCK.
+operator.
C<err> is a low-precedence variant of the C<//> operator:
see C<perlop> for details.
+=head2 the 'state' feature
+
+C<use feature 'state'> tells the compiler to enable C<state>
+variables.
+
+See L<perlsub/"Persistent Private Variables"> for details.
+
=head1 FEATURE BUNDLES
It's possible to load a whole slew of features in one go, using
a I<feature bundle>. The name of a feature bundle is prefixed with
a colon, to distinguish it from an actual feature. At present, the
-only feature bundle is C<use feature ":5.10">, which is equivalent
-to C<use feature qw(switch ~~ say err)>.
+only feature bundles are C<use feature ":5.10"> and C<use feature ":5.10.0">,
+which both are equivalent to C<use feature qw(switch say err state)>.
+
+In the forthcoming 5.10.X perl releases, C<use feature ":5.10"> will be
+equivalent to the latest C<use feature ":5.10.X">.
=cut
sub import {
my $class = shift;
if (@_ == 0) {
- require Carp;
- Carp->import("croak");
croak("No features specified");
}
while (@_) {
my $name = shift(@_);
if ($name =~ /^:(.*)/) {
if (!exists $feature_bundle{$1}) {
- require Carp;
- Carp->import("croak");
- croak(sprintf('Feature bundle "%s" is not supported by Perl %vd',
- $1, $^V));
+ unknown_feature_bundle($1);
}
unshift @_, @{$feature_bundle{$1}};
next;
}
if (!exists $feature{$name}) {
- require Carp;
- Carp->import("croak");
- croak(sprintf('Feature "%s" is not supported by Perl %vd',
- $name, $^V));
+ unknown_feature($name);
}
$^H{$feature{$name}} = 1;
}
my $name = shift;
if ($name =~ /^:(.*)/) {
if (!exists $feature_bundle{$1}) {
- require Carp;
- Carp->import("croak");
- croak(sprintf('Feature bundle "%s" is not supported by Perl %vd',
- $1, $^V));
+ unknown_feature_bundle($1);
}
unshift @_, @{$feature_bundle{$1}};
next;
}
if (!exists($feature{$name})) {
- require Carp;
- Carp->import("croak");
- croak(sprintf('Feature "%s" is not supported by Perl %vd',
- $name, $^V));
+ unknown_feature($name);
}
else {
delete $^H{$feature{$name}};
}
}
+sub unknown_feature {
+ my $feature = shift;
+ croak(sprintf('Feature "%s" is not supported by Perl %vd',
+ $feature, $^V));
+}
+
+sub unknown_feature_bundle {
+ my $feature = shift;
+ croak(sprintf('Feature bundle "%s" is not supported by Perl %vd',
+ $feature, $^V));
+}
+
+sub croak {
+ require Carp;
+ Carp::croak(@_);
+}
+
1;
projects / p5sagit/p5-mst-13.2.git / blobdiff