updated from Atlas repo

iterables/aritprog_v0.py

@@ -0,0 +1,24 @@
+"""
+Arithmetic progression class
+
+    >>> ap = ArithmeticProgression(1, .5, 3)
+    >>> list(ap)
+    [1.0, 1.5, 2.0, 2.5]
+
+
+"""
+
+
+class ArithmeticProgression:
+
+    def __init__(self, begin, step, end=None):
+        self.begin = begin
+        self.step = step
+        self.end = end  # None -> "infinite" series
+
+    def __iter__(self):
+        result = type(self.begin + self.step)(self.begin)
+        forever = self.end is None
+        while forever or result < self.end:
+            yield result
+            result += self.step