The image of a value of the relation's domain is a set of the values in the range that are related to that domain value.
Does the domain of this relation contain the value
The domain of this relation.
An accessor for the graph field for those rare cases where a client needs to get to it.
Return a relation that is the inverse of this one.
Is this relation empty (i.e., contains no pairs)?
An auxiliary extractor for this relation that returns the matched
t and its image as a sequence.
Return pairs that describe the mappings in this relation.
Add the pair
(t,u) to the relation and the pair
u taken from
us add the pair
(t,u) to the relation
and the pair
(u,t) to its inverse.
The range of this relation.
The size of this relation.
A relation can be used as an extractor that matches the image of the