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Mention ∅, clarify set composer semantics more

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1 parent 4128913 commit 8ece611462f2bb694dbaeee3e52713bf3b493242 @TimToady TimToady committed Sep 26, 2013
Showing with 12 additions and 4 deletions.
  1. +12 −4 S32-setting-library/Containers.pod
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16 S32-setting-library/Containers.pod
@@ -18,8 +18,8 @@ DRAFT: Synopsis 32: Setting Library - Containers.pod
Created: 19 Feb 2009 extracted from S29-functions.pod
- Last Modified: 3 Sep 2013
- Version: 41
+ Last Modified: 26 Sep 2013
+ Version: 42
If you read the HTML version, it is generated from the Pod in the specs
repository under
@@ -1186,8 +1186,16 @@ simply take the list of objects slurped in and turn them into a set.
Together these rules allow us to constructs sets and bags containing
sets and bags as elements.
-(To create a set from a list of Pairs or a hash, use a C<Set()> coercion
-rather than a constructor.)
+Use the C<set> composer to construct a set of the elements of the
+list. The empty set may be indicated with either C<set()> or C<∅>
+(U+2205 EMPTY SET).
+
+The C<set> composer will very literally make a set of whatever you
+pass it; in particular, it will make a set of Pairs if you try to
+pass it a list of Pairs (recall that a hash returns a list of Pairs
+in list context). To create a set from the keys of a list of Pairs,
+use a C<Set()> coercion rather than a constructor. Or to create a
+set from a hash, use the C<.keys> or C<:k> to extract only the keys.
=over

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