# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1480436982 -3600
# Node ID 22aea7bc1acd80b91a8cb7e7ad1c2a627ae0840e
# Parent  d16731ea85682b0ee1dd95e675bf630dfaafb9be
Moved __contains__ to the sequence module, providing an implementation.
Added tests of "in", "not in" and operator syntax.

diff -r d16731ea8568 -r 22aea7bc1acd lib/__builtins__/list.py
--- a/lib/__builtins__/list.py	Tue Nov 29 17:27:31 2016 +0100
+++ b/lib/__builtins__/list.py	Tue Nov 29 17:29:42 2016 +0100
@@ -39,7 +39,6 @@
         if args is not None:
             self.extend(args)
 
-    def __contains__(self, value): pass
     def __delitem__(self, index): pass
     def __setslice__(self, start, end, slice): pass
     def __delslice__(self, start, end): pass
diff -r d16731ea8568 -r 22aea7bc1acd lib/__builtins__/sequence.py
--- a/lib/__builtins__/sequence.py	Tue Nov 29 17:27:31 2016 +0100
+++ b/lib/__builtins__/sequence.py	Tue Nov 29 17:29:42 2016 +0100
@@ -46,6 +46,22 @@
 
         return str(b)
 
+    def __contains__(self, value):
+
+        "Return whether the list contains 'value'."
+
+        # Perform a linear search of the sequence contents.
+
+        for v in self:
+
+            # Return True if the current value is equal to the specified one.
+            # Note that this is not an identity test, but an equality test.
+
+            if v == value:
+                return True
+
+        return False
+
     def __getitem__(self, index):
 
         "Return the item or slice specified by 'index'."
diff -r d16731ea8568 -r 22aea7bc1acd tests/list.py
--- a/tests/list.py	Tue Nov 29 17:27:31 2016 +0100
+++ b/tests/list.py	Tue Nov 29 17:29:42 2016 +0100
@@ -24,3 +24,12 @@
     print l[-5]         # should raise an exception
 except IndexError, exc:
     print "l[-5]: failed with argument", exc.index
+
+print 1 in l            # True
+print 4 in l            # False
+print "four" in l       # True
+print "one" in l        # False
+print 1 not in l        # False
+print 4 not in l        # True
+print "four" not in l   # False
+print "one" not in l    # True
diff -r d16731ea8568 -r 22aea7bc1acd tests/operator_syntax.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/operator_syntax.py	Tue Nov 29 17:29:42 2016 +0100
@@ -0,0 +1,4 @@
+print 1 == 1                    # True
+print 1 != 1                    # False
+print 1 == "one"                # False
+print 1 != "one"                # True