add symmetric iteration routine, related to #5

src/dopt_basics/iteration.py

@@ -0,0 +1,19 @@
+from __future__ import annotations
+
+from collections import deque
+from collections.abc import Iterator, Sequence
+from typing import TypeVar
+
+T = TypeVar("T")
+
+
+def symmetric_iter(
+    x: Sequence[T],
+) -> Iterator[T]:
+    d = deque(x)
+
+    for idx in range(len(d)):
+        if idx % 2 == 0:
+            yield d.popleft()
+        else:
+            yield d.pop()