Add a variant of the decimal example.

pep-0343.txt

@@ -416,6 +416,20 @@ Examples
                     s += num / fact * sign
                 return +s
 
+       An alternative version of the generator saves the entire
+       context instead of just the precision attribute.  This is more
+       robust, but also more expensive, making it perhaps the better
+       choice when several attributes are modified together:
+
+        @do_template
+        def with_extra_precision(places=2):
+            oldcontext = decimal.getcontext()
+            newcontext = oldcontext.copy()
+            newcontext.prec += places
+            decimal.setcontext(newcontext)
+            yield None
+            decimal.setcontext(oldcontext)
+
 References
 
     [1] http://blogs.msdn.com/oldnewthing/archive/2005/01/06/347666.aspx