updated from Atlas repo

iterables/almost_aritprog_v6.py

@@ -0,0 +1,35 @@
+"""
+Arithmetic progression generator function.
+
+This is almost correct. The only problem is that the first
+item in the series may not be of the same type as the rest,
+an this may be important to the user::
+
+    >>> ap = aritprog_gen(1, .5, 3)
+    >>> list(ap)
+    [1, 1.5, 2.0, 2.5]
+    >>> ap = aritprog_gen(0, 1/3, 1)
+    >>> list(ap)
+    [0, 0.3333333333333333, 0.6666666666666666]
+    >>> from fractions import Fraction
+    >>> ap = aritprog_gen(0, Fraction(1, 3), 1)
+    >>> list(ap)
+    [0, Fraction(1, 3), Fraction(2, 3)]
+    >>> from decimal import Decimal
+    >>> ap = aritprog_gen(0, Decimal('.1'), .3)
+    >>> list(ap)
+    [0, Decimal('0.1'), Decimal('0.2')]
+
+
+"""
+
+# BEGIN ALMOST_ARITPROG_ITERTOOLS
+import itertools
+
+
+def aritprog_gen(begin, step, end=None):
+    ap_gen = itertools.count(begin, step)
+    if end is not None:
+        ap_gen = itertools.takewhile(lambda n: n < end, ap_gen)
+    return ap_gen
+# END ALMOST_ARITPROG_ITERTOOLS