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/*
 * Copyright (c) 2013, SRI International
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 * Licensed under the The BSD 3-Clause License;
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package com.sri.ai.grinder.sgdpll.group;

import java.util.Random;

import com.google.common.annotations.Beta;
import com.sri.ai.expresso.api.Expression;
import com.sri.ai.grinder.api.Context;

/**
 * Object representing an associative commutative group.
 * 
 * @author braz
 *
 */
@Beta
public interface AssociativeCommutativeGroup {
	
	/** The group identity element. */
	Expression additiveIdentityElement();

	/**
	 * Indicates whether given value is an absorbing element of the group's additive operation,
	 * that is, using the additive operation on it with any other value will produce itself.
	 * The reason this is a test on a value instead of a method providing the absorbing element
	 * is that a group is not required to have one, in which case a test can just return false 
	 * every time.
	 */
	boolean isAdditiveAbsorbingElement(Expression value);
	
	/**
	 * Performs the group's additive operation on two values.
	 */
	Expression add(Expression value1, Expression value2, Context context);

	/**
	 * The result of adding a value to itself n times, where both value and n may be symbolic expressions.
	 */
	Expression addNTimes(Expression value, Expression n, Context context);

	/** Indicates whether group's operator is idempotent. */
	boolean isIdempotent();
	
	/**
	 * Makes a random constant in the group's set of elements.
	 * This is useful for random test generation.
	 * @return
	 */
	Expression makeRandomConstant(Random random);
}