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General classes for dealing with social choice theory.

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package io.github.oliviercailloux.j_voting.preferences;

import java.util.Set;

import com.google.common.graph.Graph;

import io.github.oliviercailloux.j_voting.Alternative;
import io.github.oliviercailloux.j_voting.Voter;

/**
 *
 * Preference Interface is used to define the order chosen by a Voter between
 * some alternatives.
 *
 * A preference is empty iff it contains no alternative, equivalently, iff it
 * contains no edge (an edge between a and b means that a
 * is at least as good as b).
 *
 * A preference is associated to a Voter, which is established at construction
 * and never changes. The default voter is {@link Voter#ZERO}.
 *
 */
public interface Preference {

	/**
	 * In the graph : a relation from a to b means "a is at least as
	 * good as b". This graph can’t be modified, but is not necessarily immutable.
	 * Reflexive and transitive.
	 *
	 * @return the Graph corresponding to the Preference
	 *
	 */
	public Graph asGraph();

	/**
	 * The returned set reads through this object: if this object is mutable, any
	 * modification to this object modifies the returned set, and conversely.
	 *
	 * @return alternatives's set
	 */
	public Set getAlternatives();

	/**
	 *
	 * @return Voter instance of the preference, Returns the voter 0 if
	 *         no specific voter is associated to this preference
	 */
	public Voter getVoter();
}