# HG changeset patch
# User nishanth
# Date 1284569239 -19800
# Node ID e75538bca17804756776f1934e95a8697e69eb74
# Parent  7bc28afff7ab6afb157529e2f09177ba6049f1ff
added subsets and changed the ordering

diff -r 7bc28afff7ab -r e75538bca178 sets.rst
--- a/sets.rst	Wed Sep 15 22:09:31 2010 +0530
+++ b/sets.rst	Wed Sep 15 22:17:19 2010 +0530
@@ -30,30 +30,6 @@
 f10 is the set of fibonacci numbers from 1 to 10.
 p10 is the set of prime numbers from 1 to 10.
 
-Sets can be iterated upon just like lists and tuples. 
-::
-
-    for i in f10:
-        print i,
-
-prints the elements of f10.
-
-The length and containership check on sets is similar as in lists and tuples.
-::
-
-    len(f10)
-
-shows 5. And
-::
-
-    2 in f10
-
-prints False
-
-The order in which elements are organised in a set is not to be relied upon 
-since sets do not support indexing. Hence, slicing and striding are not valid
-on sets.
-
 Various operations that we do on sets are possible here also.
 The | character stands for union
 ::
@@ -83,6 +59,51 @@
 is all the elements in f10 union p10 but not in f10 intersection p10. In
 mathematical terms, it gives the symmectric difference.
 
+Sets also support checking of subsets.
+::
+
+    b = set([1, 2])
+    b < f10
+
+gives a True since b is a proper subset of f10.
+Similarly,
+::
+
+    f10 < f10
+
+gives a False since f10 is not a proper subset.
+hence the right way to do would be
+::
+
+    f10 <= f10
+
+and we get a True since every set is a subset of itself.
+
+Sets can be iterated upon just like lists and tuples. 
+::
+
+    for i in f10:
+        print i,
+
+prints the elements of f10.
+
+The length and containership check on sets is similar as in lists and tuples.
+::
+
+    len(f10)
+
+shows 5. And
+::
+    
+    1 in f10
+    2 in f10
+
+prints True and False respectively
+
+The order in which elements are organised in a set is not to be relied upon 
+since sets do not support indexing. Hence, slicing and striding are not valid
+on sets.
+
 {{{ Pause here and try out the following exercises }}}
 
 %% 1 %% Given a list of marks, marks = [20, 23, 22, 23, 20, 21, 23] 
@@ -110,8 +131,9 @@
 
  * How to make sets from lists
  * How to input sets
+ * How to perform union, intersection and symmectric difference operations
+ * How to check if a set is a subset of other
  * The various similarities with lists like length and containership
- * How to perform union, intersection and symmectric difference operations
 
 {{{ Show the "sponsored by FOSSEE" slide }}}