Re-word the explanation of the in/not in operators for increased content
and clarity.
Add a footnote to the information on the possibility of shadowing builtins
with locals & module globals.
diff --git a/Doc/ref/ref5.tex b/Doc/ref/ref5.tex
index 93f6724..810fb1a 100644
--- a/Doc/ref/ref5.tex
+++ b/Doc/ref/ref5.tex
@@ -65,7 +65,12 @@
name throughout that code block. When it is not assigned to anywhere
in the block, or when it is assigned to but also explicitly listed in
a \keyword{global} statement, it refers to a global name if one exists,
-else to a built-in name (and this binding may dynamically change).
+else to a built-in name (and this binding may dynamically
+change).\footnote{The Python interpreter provides a useful set of
+ predefined built-in functions. It is not recommended to reuse
+ (hide) these names with self defined objects. See the
+ \citetitle[../lib/built-in-funcs.html]{Python Library Reference} for
+ the descriptions of built-in functions and methods.}
\indexii{name}{binding}
\index{code block}
\stindex{global}
@@ -757,13 +762,16 @@
\end{itemize}
The operators \keyword{in} and \keyword{not in} test for set
-membership: every type can define membership in whatever way is
-appropriate. Traditionally, this interface has been tightly bound to
-the sequence interface, which is related in that presence in a sequence
-can be usefully interpreted as membership in a set.
+membership. \code{\var{x} in \var{s}} evaluates to true if \var{x}
+is a member of the set \var{s}, and false otherwise. \code{\var{x}
+not in \var{s}} returns the negation of \code{\var{x} in \var{s}}.
+The set membership test has traditionally been bound to sequences; an
+object is a member of a set if the set is a sequence and contains an
+element equal to that object. However, it is possible for an object
+to support membership tests without being a sequence.
For the list and tuple types, \code{\var{x} in \var{y}} is true if and
-only if there exists such an index \var{i} such that
+only if there exists an index \var{i} such that
\code{\var{x} == \var{y}[\var{i}]} is true.
For the Unicode and string types, \code{\var{x} in \var{y}} is true if