relation_list.py

from pymwp import RelationList

RelationList

RelationList(
    variables: Optional[List[str]] = None,
    relation_list: Optional[List[Relation]] = None,
)

Relation list holds a list of Relations. It provides methods for performing operations collectively on all relations in the list.

Attributes:

Name	Type	Description
relations	List[Relation]	List of relations.

To create a relations list, specify either variables or relation_list.

Parameters:

Name	Type	Description	Default
variables	Optional[List[str]]	List of variables used to initialize a relation on relation list.	None
relation_list	Optional[List[Relation]]	List of relations for initializing relation list.	None

Specifying a relation_list argument of a list of Relations, initializes a RelationList containing the provided relations. If no relation_list argument is provided, the constructor will create a relation list with one relation, using the provided variables to initialize that relation.

Example

Create relation list using specific variables

rel_list = RelationList(['X0', 'X1', 'X2'])

Generates a list with 1 relation:

X0 |  +o  +o  +o
X1 |  +o  +o  +o
X2 |  +o  +o  +o

Create relation list by providing relations

relations = [Relation(['X0', 'X1']), Relation(['X0'])]
rel_list = RelationList(relation_list=relations)

Generates a list with 2 relations:

1:      X0  |  +o  +o
        X1  |  +o  +o

2:      X0  |  +o

If no arguments are provided, the result is a relation list with an empty relation.

rel_list = RelationList()

Generates a list with 1 empty relation.

first property

first: Relation

Gets the first relation in relation list.

composition

composition(other: RelationList) -> None

Apply composition to all relations in two relation lists.

This method takes as argument other relation list, then composes the product of self and other by computing the product of each relation, for all combinations.

Composition occurs in place. After composition self will contain all unique relations obtained during composition.

To compose RelationList and a single Relation, see one_composition().

Parameters:

Name	Type	Description	Default
other	RelationList	RelationList to compose with self	required

contains_matrix staticmethod

contains_matrix(search_in: List[Relation], matrix: List[List]) -> bool

Check if a list of relations contains the provided matrix.

Parameters:

Name	Type	Description	Default
search_in	List[Relation]	list of relations to search	required
matrix	List[List]	search value to look for	required

Returns:

Type	Description
bool	True if matrix is found somewhere in the list of relations and False otherwise.

fixpoint

fixpoint() -> None

Apply fixpoint to all relations in relation list.

identity staticmethod

identity(variables: List[str]) -> RelationList

Create relation list that contains 1 identity relation.

This is an alternative way to construct a relation list.

Example

Create relation list containing an identity relation

rel_list = RelationList.identity(['X0', 'X1', 'X2'])

Generates a list with 1 identity relation:

X0 |  +m  +o  +o
X1 |  +o  +m  +o
X2 |  +o  +o  +m

Parameters:

Name	Type	Description	Default
variables	List[str]	A list of variables.	required

Returns:

Type	Description
RelationList	RelationList that contains identity relation generated using the provided variables.

loop_correction

loop_correction(x_var: str, dg: DeltaGraph) -> None

Apply loop correction.

one_composition

one_composition(relation: Relation) -> None

Compose each relation in a relation list × relation.

This method iterates current relation list and applies composition() to each of its relations, using argument relation as the other operand.

Parameters:

Name	Type	Description	Default
relation	Relation	relation to compose with relations in current list.	required

replace_column

replace_column(vector: list, variable: str) -> None

For each relation in a relation list, replace column with a provided vector, in place.

This method takes as input a variable, then finds the index of that variable based on its name, then applies the column replacement at the discovered index.

Parameters:

Name	Type	Description	Default
vector	list	vector that will replace a column	required
variable	str	variable value; replace will occur at the index of this variable.	required

Raises:

Type	Description
ValueError	if variable does not exists some relation belonging to this relation list.

show

show() -> None

Display relation list.

while_correction

while_correction(dg: DeltaGraph) -> None

Apply while_correction() to all relations in a relation list.