- Type Parameters:
N- Node parameter type
- All Known Subinterfaces:
- All Known Implementing Classes:
@Beta @DoNotMock("Implement with a lambda, or use GraphBuilder to build a Graph with the desired edges") public interface PredecessorsFunction<N>A functional interface for graph-structured data.
This interface is meant to be used as the type of a parameter to graph algorithms (such as topological sort) that only need a way of accessing the predecessors of a node in a graph.
UsageGiven an algorithm, for example:
you will invoke it depending on the graph representation you're using.
public <N> someGraphAlgorithm(N startNode, PredecessorsFunction<N> predecessorsFunction);
This works because those types each implement
PredecessorsFunction. It will also work with any other implementation of this interface.
If you have your own graph implementation based around a custom node type
MyNode, which has a method
getParents()that retrieves its predecessors in a graph:
If you have some other mechanism for returning the predecessors of a node, or one that doesn't return a
Iterable<? extends N>, then you can use a lambda to perform a more general transformation:
someGraphAlgorithm(startNode, node -> ImmutableList.of(node.mother(), node.father()));
Graph algorithms that need additional capabilities (accessing both predecessors and successors, iterating over the edges, etc.) should declare their input to be of a type that provides those capabilities, such as
- Joshua O'Madadhain, Jens Nyman
Iterable<? extends N> predecessors(N node)Returns all nodes in this graph adjacent to
nodewhich can be reached by traversing
node's incoming edges against the direction (if any) of the edge.
Some algorithms that operate on a
PredecessorsFunctionmay produce undesired results if the returned
Iterablecontains duplicate elements. Implementations of such algorithms should document their behavior in the presence of duplicates.
The elements of the returned
Iterablemust each be:
- Usable as
Mapkeys (see the Guava User Guide's section on graph elements for details)
nodeis not an element of this graph