Adding examples of casting among lazyfiable objects

Which refs #2139

I won't close until we decide if we leave it here or move to the new
Iterating page, since this not only refers to lists, but also to Seqs
and Maps.

Author: JJ

doc/Language/list.pod6

@@ -229,13 +229,13 @@ value, but unlike the above options, it will break L<Scalars|/type/Scalar>.
     say (1, |$(2, 3), 4) eqv (1, 2, 3, 4);       # OUTPUT: «True␤»
     say (1, slip($(2, 3)), 4) eqv (1, 2, 3, 4);  # OUTPUT: «False␤»
 
-X<|laziness in iterable objects>
+X<|laziness in Iterable objects>
 =head1 Lazy lists
 
-C<List>s, C<Seq>s (and any class that subclasses them, like C<Array>s) and
-any other class thet implements the L<Iterable> role can be lazy, which means that their
-values are computed on demand and stored for later use. To create a lazy object
-use L<gather/take|/language/control#gather/take> or the L<sequence
+C<List>s, C<Seq>s (and any class that subclasses them, like C<Array>s) and any
+other class thet implements the L<Iterable> role can be lazy, which means that
+their values are computed on demand and stored for later use. To create a lazy
+object use L<gather/take|/language/control#gather/take> or the L<sequence
 operator|/language/operators#infix_...>. You can also write a class that
 implements the role L<Iterator|/type/Iterator> and returns C<True> on a call to
 L<is-lazy|/routine/is-lazy>. Please note that some methods like C<elems> cannot
@@ -252,24 +252,31 @@ L<Exception|/type/Exception>.
     # Once all elements have been retrieved, the List
     # is no longer considered lazy.
 
-    my @no-longer-lazy = eager @lazy-array;           # Forcing eager evaluation
+    my @no-longer-lazy = eager @lazy-array;  # Forcing eager evaluation
     say @no-longer-lazy.is-lazy;             # OUTPUT: «False␤»
     say @no-longer-lazy[];
     # OUTPUT: (sequence starting with «[1 11 121» ending with a 300 digit number)
 
 In the example above, C<@lazy-array> is an C<Array> which, through construction,
-is make C<lazy>. When using it with C<is-lazy> it is returning an iterator,
+is made C<lazy>. When calling C<is-lazy> on it it is returning an C<Iterator>,
 which, since it originates in a lazy list, is itself lazy.
 
-A common use case for lazy C<List>s is the processing of infinite sequences of
+A common use case for lazy C<Seq>s is the processing of infinite sequences of
 numbers, whose values have not been computed yet and cannot be computed in their
 entirety. Specific values in the List will only be computed when they are
 needed.
 
-    my @l = 1, 2, 4, 8 ... Inf;
-    say @l[0..16];
+    my  $l := 1, 2, 4, 8 ... Inf;
+    say $l[0..16];
     # OUTPUT: «(1 2 4 8 16 32 64 128 256 512 1024 2048 4096 8192 16384 32768 65536)␤»
 
+You can easily assign lazy objects to other objects, conserving their laziness:
+
+    my  $l := 1, 2, 4, 8 ... Inf; # This is a lazy Seq.
+    my  @lazy-array = $l;
+    say @lazy-array[10..15]; # OUTPUT: «(1024 2048 4096 8192 16384 32768)␤»
+    say @lazy-array.is-lazy; # OUTPUT: «True␤»
+
 =head1 Immutability
 
 The lists we have talked about so far (C<List>, C<Seq> and C<Slip>)
@@ -289,7 +296,7 @@ can still change the value which that C<Scalar> points to:
     (1, $a, 3)[1] = 42;
     $a.say;            # OUTPUT: «42␤»
 
-...that is, it is only the list structure itself – how many elements there are
+that is, it is only the list structure itself – how many elements there are
 and each element's identity – that is immutable.  The immutability is not
 contagious past the identity of the element.