Adding memoized functions

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

+# 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

[stgao, 2016/12/05 19:30:56]

style nit: for top-level definition, if it is not to be used by other modules,
we usually prefix the name with underscore. For this case, we usually do:
_F = ...
-G = ...

+G = lambda x: x * x
+
+
+class FunctionsTest(unittest.TestCase):
+
+  def testFunctionCall(self):
+    """``Function.__call__`` returns same value as the underlying callable."""
+    self.assertEqual(F(5), Function(F)(5))
+    self.assertEqual(G(5), Function(G)(5))
+
+  def testFunctionMap(self):
+    """``Function.map`` composes functions as described in the docstring."""
+    self.assertEqual(G(F(5)), Function(F).map(G)(5))
+    self.assertEqual(F(G(5)), Function(G).map(F)(5))
+
+  def testMemoizedFunctionCall(self):
+    """``MemoizedFunction.__call__`` returns same value as its callable."""
+    self.assertEqual(F(5), MemoizedFunction(F)(5))
+    self.assertEqual(G(5), MemoizedFunction(G)(5))
+
+  def testMemoizedFunctionMap(self):
+    """``MemoizedFunction.map`` composes functions as described."""
+    self.assertEqual(G(F(5)), MemoizedFunction(F).map(G)(5))
+    self.assertEqual(F(G(5)), MemoizedFunction(G).map(F)(5))
+
+  def testMemoization(self):
+    """``MemoizedFunction.__call__`` actually does memoize.
+
+    That is, we call the underlying function once (to set the memo), then
+    we discard the underlying function (to be sure the next ``__call__``
+    is handled from the memos, and finally call the function to check.
+    """
+    f = MemoizedFunction(F)
+    f(5)
+    del f._f
+    self.assertEqual(F(5), f(5))
+
+  def testClearMemos(self):
+    """``MemoizedFunction._ClearMemos`` does actually clear the memos.
+
+    That is, we call the underlying function once (to set the memo),
+    then swap put the underlying function with a different one (to be
+    sure we know whether the next ``__call__`` goes to the memos or to
+    the function), and finally clear the memos and check.
+    """
+    f = MemoizedFunction(F)
+    f(5)
+    f._f = G
+    f._ClearMemos()
+    self.assertEqual(G(5), f(5))