Immutable list based on LBST

immutables/__init__.py

@@ -15,11 +15,13 @@
         import collections.abc as _abc
         _abc.Mapping.register(Map)
 
+from .list import List
+
 from ._protocols import MapKeys as MapKeys
 from ._protocols import MapValues as MapValues
 from ._protocols import MapItems as MapItems
 from ._protocols import MapMutation as MapMutation
 
 from ._version import __version__
 
-__all__ = 'Map',
+__all__ = 'Map', 'List'

immutables/lbst.py

@@ -0,0 +1,158 @@
+from collections import namedtuple
+from math import log2
+
+#
+# Balanced binary tree based on Log-Balanced Search Trees (LBST)
+# and slib's wttree
+#
+# ref: https://scholar.google.fr/scholar?cluster=16806430159882137269
+#
+
+LBST = namedtuple('LBST', 'comparator root')
+
+Node = namedtuple('Node', 'key value weight left right')
+
+
+NODE_NULL = Node(None, None, 0, None, None)
+
+
+def make(comparator):
+    return LBST(comparator, NODE_NULL)
+
+
+def _node_weight(node):
+    return node.weight
+
+
+def _is_less(a, b):
+    assert isinstance(a, int)
+    assert isinstance(b, int)
+
+    # `a` is less than `b`, when the position of the left-most bit set
+    # of `a` is less than the position of the left-most bit set of `b`;
+    # the left-most bit set position is given by int.bit_length (3.1+)
+    return a.bit_length() < b.bit_length()
+
+
+def _is_too_big(a, b):
+    return _is_less(a, b >> 1)
+
+
+def _node_join(key, value, left, right):
+    return Node(key, value, _node_weight(left) + _node_weight(right) + 1, left, right)
+
+
+def _node_single_left_rotation(key, value, left, right):
+    return _node_join(right.key, right.value, _node_join(key, value, left, right.left), right.right)
+
+
+def _node_double_left_rotation(key, value, left, right):
+    return _node_join(
+        right.left.key,
+        right.left.value,
+        _node_join(key, value, left, right.left.left),
+        _node_join(right.key, right.value, right.left.right, right.right)
+    )
+
+
+def _node_single_right_rotation(key, value, left, right):
+    return _node_join(left.key, left.value, left.left, _node_join(key, value, left.right, right))
+
+
+def _node_double_right_rotation(key, value, left, right):
+    return _node_join(
+        left.right.key,
+        left.right.value,
+        _node_join(left.key, left.value, left.left, left.right.left),
+        _node_join(key, value, left.right.right, right)
+    )
+
+
+def _node_rebalance(key, value, left, right):
+    if _is_too_big(_node_weight(left), _node_weight(right)):
+        # right is too big, does it require one or two rotations?
+        if not _is_less(_node_weight(right.right), _node_weight(right.left)):
+            return _node_single_left_rotation(key, value, left, right)
+        else:
+            return _node_double_left_rotation(key, value, left, right)
+
+    if _is_too_big(_node_weight(right), _node_weight(left)):
+        # left is too big, does it require one or two rotations?
+        if not _is_less(_node_weight(left.left), _node_weight(left.right)):
+            return _node_single_right_rotation(key, value, left, right)
+        else:
+            return _node_double_right_rotation(key, value, left, right)
+
+    # both sides are the same weight, join the two trees with a top
+    # level node.
+    return Node(key, value, _node_weight(left) + _node_weight(right) + 1, left, right)
+
+
+def _node_set(node, comparator, key, value):
+    if node is NODE_NULL:
+        return Node(key, value, 1, NODE_NULL, NODE_NULL)
+
+    if comparator(key, node.key):
+        # The given KEY is less that node.key, recurse left side.
+        return _node_rebalance(
+            node.key,
+            node.value,
+            _node_set(node.left, comparator, key, value),
+            node.right
+        )
+
+    if comparator(node.key, key):
+        # The given KEY is more than node.key, recurse right side.
+        return _node_rebalance(
+            node.key,
+            node.value,
+            node.left,
+            _node_set(node.right, comparator, key, value)
+        )
+
+    # otherwise, `key` is equal to `node.key`, create a new node with
+    # the given `value`.
+
+    return Node(key, value, _node_weight(node.left) + _node_weight(node.right) + 1, node.left, node.right)
+
+
+def set(lbst, key, value):
+    if lbst.root is NODE_NULL:
+        return LBST(lbst.comparator, Node(key, value, 1, NODE_NULL, NODE_NULL))
+
+    return LBST(lbst.comparator, _node_set(lbst.root, lbst.comparator, key, value))
+
+
+def _node_to_dict(node, out):
+    if node.left is not NODE_NULL:
+        _node_to_dict(node.left, out)
+
+    out[node.key] = node.value
+
+    if node.right is not NODE_NULL:
+        _node_to_dict(node.right, out)
+
+
+def to_dict(lbst):
+    # The created dict is sorted according to `lbst.comparator`.
+    out = dict()
+    _node_to_dict(lbst.root, out)
+    return out
+
+
+def _node_is_balanced(node):
+    if node is NODE_NULL:
+        return True
+
+    out = (
+        not _is_too_big(_node_weight(node.left), _node_weight(node.right))
+        and not _is_too_big(_node_weight(node.right), _node_weight(node.left))
+        and _node_is_balanced(node.right)
+        and _node_is_balanced(node.left)
+    )
+
+    return out
+
+
+def is_balanced(lbst):
+    return _node_is_balanced(lbst.root)

immutables/list.py

@@ -0,0 +1,2 @@
+class List():
+    pass

tests/_test_list.py

@@ -0,0 +1,153 @@
+import pytest
+
+from immutables import List
+
+
+def test_empty():
+    ilist = List()
+
+    assert list(ilist) == []
+
+
+def test_create():
+    ilist = List(range(10))
+
+    assert list(ilist) == list(range(10))
+
+
+def test_getitem():
+    ilist = List(range(10))
+
+    assert ilist[5] == 4
+
+
+def test_getitem_indexerror():
+    ilist = List(range(10))
+
+    with pytest.raises(IndexError):
+        ilist[10]
+
+
+def test_slice_end():
+    ilist = List(range(10))
+
+    assert list(ilist[:5]) == list(range(10)[:5])
+
+
+def test_slice_begin():
+    ilist = List(range(10))
+
+    assert list(ilist[5:]) == list(range(10)[5:])
+
+
+def test_slice_begin_end():
+    ilist = List(range(10))
+
+    assert list(ilist[3:6]) == list(range(10)[3:6])
+
+
+def test_slice_step():
+    ilist = List(range(10))
+
+    assert list(ilist[::2]) == list(range(10)[::2])
+
+
+def test_slice_begin_end_step():
+    ilist = List(range(10))
+
+    assert list(ilist[3:6:2]) == list(range(10)[3:6:2])
+
+
+def test_slice_begin_end_negative_step():
+    ilist = List(range(10))
+
+    assert list(ilist[3:6:-1]) == list(range(10)[3:6:-1])
+
+
+def test_append_empty():
+    ilist = List()
+
+    ilist = ilist.append(42)
+
+    assert ilist[0] == 42
+
+
+def test_append():
+    ilist = List(range(10))
+
+    ilist = ilist.append(42)
+
+    assert ilist[10] == 42
+    assert list(ilist) == list(range(10)) + [42]
+
+
+def test_extend_empty():
+    ilist = List()
+    ilist = ilist.extend(list(range(10)))
+
+    assert list(ilist) == list(range(10))
+
+
+def test_extend():
+    ilist = List(range(10))
+    ilist = ilist.extend(ilist)
+
+    assert list(ilist) == list(range(10)) + list(range(10))
+
+
+def test_insert():
+    ilist = List(range(10))
+    ilist = ilist.insert(5, 42)
+
+    assert list(ilist) == [0, 1, 2, 3, 4, 42, 5, 6, 7, 8, 9]
+
+
+def test_remove():
+    ilist = [42, 1337, 2006]
+    ilist = ilist.remove(42)
+
+    assert list(ilist) == [42, 2006]
+
+
+def test_remove_valueerror():
+    ilist = List(range(10))
+
+    with pytest.raises(ValueError):
+        ilist = ilist.remove(42)
+
+
+def test_pop():
+    ilist = List(range(10))
+    ilist, value = ilist.pop()
+
+    assert list(ilist) == list(range(9))
+    assert value == 9
+
+
+def test_pop_indexerror:
+    ilist = List()
+
+    with pytest.raises(IndexError):
+        ilist.pop()
+
+
+def test_pop_head():
+    ilist = List(range(10))
+    ilist, value = ilist.pop(0)
+
+    assert list(ilist) == list(range(1,10))
+    assert value == 0
+
+
+def test_replace():
+    ilist = List(range(10))
+    ilist = ilist.replace(5, 42)
+
+    assert list(ilist) = [0, 1, 2, 3, 4, 42, 6, 7, 8, 9]
+
+
+def test_replace_indexerror():
+    ilist = List()
+
+    with pytest.raises(IndexError):
+        ilist.replace(42, 42)