less useful

From: "Joshua ben Jore" <twists@gmail.com>
Message-ID: <dc5c751d0701061333w7b89ea48kf5c8993e3de19b44@mail.gmail.com>

p4raw-id: //depot/perl@29709

1 files changed, 135 insertions, 5 deletions

diff --git a/lib/less.pm b/lib/less.pm
index de0ac8f423..085e971219 100644
--- a/lib/less.pm
+++ b/lib/less.pm
@@ -1,24 +1,154 @@
 package less;
+use strict;
+use warnings;
 
-our $VERSION = '0.01';
+our $VERSION = '0.02';
+
+sub _pack_tags {
+    return join ' ', @_;
+}
+
+sub _unpack_tags {
+    return grep { defined and length }
+        map  { split ' ' }
+        grep {defined} @_;
+}
+
+sub of {
+    my $class = shift @_;
+
+    # If no one wants the result, don't bother computing it.
+    return unless defined wantarray;
+
+    my $hinthash = ( caller 0 )[10];
+    my %tags;
+    @tags{ _unpack_tags( $hinthash->{$class} ) } = ();
+
+    if (@_) {
+        exists $tags{$_} and return !!1 for @_;
+        return;
+    }
+    else {
+        return keys %tags;
+    }
+}
+
+sub import {
+    my $class = shift @_;
+
+    @_ = 'please' if not @_;
+    my %tags;
+    @tags{ _unpack_tags( @_, $^H{$class} ) } = ();
+
+    $^H{$class} = _pack_tags( keys %tags );
+    return;
+}
+
+sub unimport {
+    my $class = shift @_;
+
+    if (@_) {
+        my %tags;
+        @tags{ _unpack_tags( $^H{$class} ) } = ();
+        delete @tags{ _unpack_tags(@_) };
+        my $new = _pack_tags( keys %tags );
+
+        if ( not length $new ) {
+            delete $^H{$class};
+        }
+        else {
+            $^H{$class} = $new;
+        }
+    }
+    else {
+        delete $^H{$class};
+    }
+
+    return;
+}
+
+__END__
 
 =head1 NAME
 
-less - perl pragma to request less of something from the compiler
+less - perl pragma to request less of something
 
 =head1 SYNOPSIS
 
-    use less;  # unimplemented
+    use less 'CPU';
 
 =head1 DESCRIPTION
 
-Currently unimplemented, this may someday be a compiler directive
-to make certain trade-offs, such as perhaps
+This is a user-pragma. If you're very lucky some code you're using
+will know that you asked for less CPU usage or ram or fat or... we
+just can't know. Consult your documentation on everything you're
+currently using.
+
+For general suggestions, try requesting C<CPU> or C<memory>.
 
     use less 'memory';
     use less 'CPU';
     use less 'fat';
 
+If you ask for nothing in particular, you'll be asking for C<less
+'please'>.
+
+    use less 'please';
+
+=head1 FOR MODULE AUTHORS
+
+L<less> has been in the core as a "joke" module for ages now and it
+hasn't had any real way to communicating any information to
+anything. Thanks to Nicholas Clark we have user pragmas (see
+L<perlpragma>) and now C<less> can do something.
+
+You can probably expect your users to be able to guess that they can
+request less CPU or memory or just "less" overall.
+
+If the user didn't specify anything, it's interpreted as having used
+the C<please> tag. It's up to you to make this useful.
+
+  # equivalent
+  use less;
+  use less 'please';
+
+=head2 C<< BOOLEAN = less->of( FEATURE ) >>
+
+The class method C<< less->of( NAME ) >> returns a boolean to tell you
+whether your user requested less of something.
+
+  if ( less->of( 'CPU' ) ) {
+      ...
+  }
+  elsif ( less->of( 'memory' ) ) {
+
+  }
+
+=head2 C<< FEATURES = less->of() >>
+
+If you don't ask for any feature, you get the list of features that
+the user requested you to be nice to. This has the nice side effect
+that if you don't respect anything in particular then you can just ask
+for it and use it like a boolean.
+
+  if ( less->of ) {
+      ...
+  }
+  else {
+      ...
+  }
+
+=head1 CAVEATS
+
+=over
+
+=item This probably does nothing.
+
+=item This works only on 5.10+
+
+At least it's backwards compatible in not doing much.
+
+=back
 
 =cut