Adding memoized functions

appengine/findit/libs/math/test/functions_test.py

Index: appengine/findit/libs/math/test/functions_test.py
diff --git a/appengine/findit/libs/math/test/functions_test.py b/appengine/findit/libs/math/test/functions_test.py
new file mode 100644
index 0000000000000000000000000000000000000000..6cbce2c03bf7991ef5b41a67f842fab5f521bded
--- /dev/null
+++ b/appengine/findit/libs/math/test/functions_test.py
@@ -0,0 +1,43 @@
+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import unittest
+
+from libs.math.functions import Function
+from libs.math.functions import MemoizedFunction
+
+# Some arbitrary functions:
+F = lambda x: x + 1
+G = lambda x: x * x
+

[Sharu Jiang, 2016/12/02 23:47:18]

nit: 2 lines

[wrengr, 2016/12/05 18:50:45]

Done.

+class FunctionsTest(unittest.TestCase):

[Martin Barbella, 2016/12/02 23:50:21]

Same nits for whitespace and docstrings.

[wrengr, 2016/12/05 18:50:45]

Done.

+
+  def testFunctionCall(self):
+    self.assertEqual(F(5), Function(F)(5))
+    self.assertEqual(G(5), Function(G)(5))
+
+  def testFunctionMap(self):
+    self.assertEqual(G(F(5)), Function(F).map(G)(5))
+    self.assertEqual(F(G(5)), Function(G).map(F)(5))
+
+  def testMemoizedFunctionCall(self):
+    self.assertEqual(F(5), MemoizedFunction(F)(5))
+    self.assertEqual(G(5), MemoizedFunction(G)(5))
+
+  def testMemoizedFunctionMap(self):
+    self.assertEqual(G(F(5)), MemoizedFunction(F).map(G)(5))
+    self.assertEqual(F(G(5)), MemoizedFunction(G).map(F)(5))
+
+  def testMemoization(self):
+    f = MemoizedFunction(F)
+    f(5) # Call it once, to make a memo
+    del f._f # Discard the function (to be sure the next call comes form memos)

[inferno, 2016/12/05 00:02:10]

Put comment in previous line ending with period., same for next line as well.
typo: from.

[wrengr, 2016/12/05 18:50:45]

Done.

+    self.assertEqual(F(5), f(5))
+
+  def testClearMemos(self):
+    f = MemoizedFunction(F)
+    f(5) # Call it once, to make a memo

[inferno, 2016/12/05 00:02:10]

Put comment in previous line ending with period., same for next line as well.

[wrengr, 2016/12/05 18:50:45]

Done.

+    f._f = G # Change the function, so it's different than the memos.

[Sharu Jiang, 2016/12/02 23:47:18]

Is changing _f only for testing or it can be actually used, if so, we should add
a setter for it.

[wrengr, 2016/12/05 18:50:45]

Changing _f is only for testing. Ideally there should be no _f at all, just self
(cf., https://crbug.com/671275)

+    f._ClearMemos()
+    self.assertEqual(G(5), f(5))