Add sequences module

bareon_dynamic_allocator/sequences.py

@@ -0,0 +1,67 @@
+#    Copyright 2016 Mirantis, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See then
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import math
+
+
+class BaseSequence(object):
+
+    def __init__(self, n):
+        self.n = n
+        self.n_current = 0
+        self.current = 1
+        self.previous = 0
+
+    def __iter__(self):
+        return self
+
+    def next(self):
+        self.previous = self.current
+        self.current += 1
+        return self.current
+        
+
+class CrossSumInequalitySequence(BaseSequence):
+    """An implementaion of a sequence from 1 to n
+
+    http://math.stackexchange.com/a/1596812/301008
+    """
+
+    def next(self):
+        if self.n_current >= self.n:
+            raise StopIteration
+        else:
+            self.previous = int(math.floor((self.current + 1) / 2.0) *
+                            math.floor((self.current + 2) / 2.0))
+            self.n_current += 1
+            self.current += 1
+
+            return self.previous
+
+
+class FibonacciSequence(BaseSequence):
+    """Iterator over a sequence of Fibonacci numbers with n elements from 1 to n
+    """
+    def __init__(self, n):
+        super(FibonacciSequence, self).__init__(n)
+        self.previous = 0
+        self.current = 1
+
+    def next(self):
+        if self.n_current > self.n:
+            raise StopIteration
+        else:
+            self.n_current += 1
+            self.previous, self.current = self.current, self.current + self.previous
+            return self.current