Tangle#

class tangles.Tangle(agreement: int, core: set[tuple[int, int]] | None = None, parent: Tangle | None = None)#

A node in the tangle search tree. It represents a tangle.

The path of the tangle search tree from the root to this node determines the features in this tangle: Each edge on the path determines the orientation of a separation.

More precisely, if the path contains an edge from a node on tree level \(k-1\) to a node on tree level \(k\) which is a left child, then this tangle contains the left orientation of the separation corresponding to tree level \(k\) (and vice versa for a right child).

Attributes#

parentTangle or None: The parent in the tangle search tree. It is a tangle that orients every separation except for the highest order separation of this tangle. None if the tangle is the root tangle.
left_childTangle or None: The left child in the tangle search tree. It is a tangle that orients one more separation than this tangle. The left child orients this additional separation to the left. None if there is no left child.
right_childTangle or None: The right child in the tangle search tree. It is a tangle that orients one more separation than this tangle. The right child orients this additional separation to the right. None if there is no right child.
coreset[OrientedSep]: The set of all minimal oriented separations contained within this tangle.
agreementint: The agreement value of this tangle.

Methods

`children()`	Return the list of children of this node
`copy()`	Create a new tangle with the same core and agreement value
`copy_subtree()`	Copy the subtree starting at this node
`copy_subtree_into_children()`	Replace each child by a copy of the subtree starting at this node
`detach()`	Detach the node by removing its pointer to its parent and the parents pointer to it
`equal_data()`	Check whether two tangles have the same data (core and agreement value)
`from_indicator_matrix()`	Turn an indicator matrix back into a binary tree
`is_leaf()`	Whether this node is a leaf
`leaves_in_subtree()`	Find all leaves in the binary tree
`level()`	Returns the level of this node
`level_in_subtree()`	Return all the nodes at a certain depth below this node
`open()`	Open the tangle by removing its children
`path_from_root_indicator()`	Returns the list of sides one has to take to go from the root to this node
`set_left_child()`	Set the left child of the node
`set_right_child()`	Set the right child of the node
`to_indicator_matrix()`	Turn a list of nodes into an indicator matrix