Merge branch 'master' of https://git.maemo.org/projects/theonering

[theonering] / src / util / algorithms.py

diff --git a/src/util/algorithms.py b/src/util/algorithms.py
index 5da8b80..040967a 100644 (file)
--- a/src/util/algorithms.py
+++ b/src/util/algorithms.py
@@ -488,3 +488,90 @@ def functional_if(combiner, preds, item):
 
        bool_results = function_map(preds, item)
        return combiner(pass_bool, bool_results)
+
+
+def pushback_itr(itr):
+       """
+       >>> list(pushback_itr(xrange(5)))
+       [0, 1, 2, 3, 4]
+       >>>
+       >>> first = True
+       >>> itr = pushback_itr(xrange(5))
+       >>> for i in itr:
+       ...     print i
+       ...     if first and i == 2:
+       ...             first = False
+       ...             print itr.send(i)
+       0
+       1
+       2
+       None
+       2
+       3
+       4
+       >>>
+       >>> first = True
+       >>> itr = pushback_itr(xrange(5))
+       >>> for i in itr:
+       ...     print i
+       ...     if first and i == 2:
+       ...             first = False
+       ...             print itr.send(i)
+       ...             print itr.send(i)
+       0
+       1
+       2
+       None
+       None
+       2
+       2
+       3
+       4
+       >>>
+       >>> itr = pushback_itr(xrange(5))
+       >>> print itr.next()
+       0
+       >>> print itr.next()
+       1
+       >>> print itr.send(10)
+       None
+       >>> print itr.next()
+       10
+       >>> print itr.next()
+       2
+       >>> print itr.send(20)
+       None
+       >>> print itr.send(30)
+       None
+       >>> print itr.send(40)
+       None
+       >>> print itr.next()
+       40
+       >>> print itr.next()
+       30
+       >>> print itr.send(50)
+       None
+       >>> print itr.next()
+       50
+       >>> print itr.next()
+       20
+       >>> print itr.next()
+       3
+       >>> print itr.next()
+       4
+       """
+       for item in itr:
+               maybePushedBack = yield item
+               queue = []
+               while queue or maybePushedBack is not None:
+                       if maybePushedBack is not None:
+                               queue.append(maybePushedBack)
+                               maybePushedBack = yield None
+                       else:
+                               item = queue.pop()
+                               maybePushedBack = yield item
+
+
+if __name__ == "__main__":
+       import doctest
+       print doctest.testmod()