No need to define the empty set (thanks @lizmat)

Also adds some text to the data structures on using eager for early reification.

Author: JJ

doc/Language/math.pod6

@@ -11,7 +11,6 @@ Perl 6 includes the L<Set> data type, as well as support for L<most set operati
 =begin code
 my @arbitrary-numbers = ^100;
 my \U = @arbitrary-numbers.Set;
-my \Ø = ().Set;
 
 my @sets;
 

doc/Language/structures.pod6

@@ -381,13 +381,13 @@ statements inside of it would've been printed right away.
 
 Another way to fully-reify a list, is by calling L«C<.elems>|/routine/elems» on
 it. This is the reason why checking whether a list contains any items is best
-done by using C<.Bool> method (or just using C<if @array { … }>), since you don't
-need to reify I<all> the elements to find out if there are C<any> of them.
+done by using C<.Bool> method (or just using C<if @array { … }>), since you
+don't need to reify I<all> the elements to find out if there are C<any> of them.
 
-There are times where you I<do> want to fully-reify a list before doing something.
-For example, the L«C<IO::Handle.lines>|/type/IO::Handle#method_lines» returns
-a L<Seq>. The following code contains a bug; keeping reification in mind, try to
-spot it:
+There are times where you I<do> want to fully-reify a list before doing
+something. For example, the L«C<IO::Handle.lines>|/type/IO::Handle#method_lines»
+returns a L<Seq>. The following code contains a bug; keeping reification in
+mind, try to spot it:
 
 =for code
 my $fh = "/tmp/bar".IO.open;
@@ -423,6 +423,14 @@ say "Read $lines.elems() lines"; #reifying before closing handle
 close $fh;
 say $lines[0]; # no problem!
 
+Using L<eager|/routine/eager> will also reify the whole sequence:
+
+=for code
+my $fh = "/tmp/bar".IO.open;
+my $lines = eager $fh.lines; # Uses eager for reification.
+close $fh;
+say $lines[0];
+
 =head1 Introspection
 
 Languages that allow