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Open-source constraint solver.
/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2023, IMT Atlantique. All rights reserved.
*
* Licensed under the BSD 4-clause license.
*
* See LICENSE file in the project root for full license information.
*/
package org.chocosolver.solver.constraints.nary.cnf;
import org.chocosolver.solver.variables.BoolVar;
import org.chocosolver.util.tools.ArrayUtils;
/**
* Logical Operator, to ease clause definition.
*
*
* @author Charles Prud'homme
* @since 23 nov. 2010
*/
public final class LogOp implements ILogical {
public enum Operator {
OR, AND;
public static Operator flip(Operator operator) {
if (Operator.OR.equals(operator)) {
return Operator.AND;
} else {
return Operator.OR;
}
}
}
public enum Type {
POSITIVE, NEGATIVE;
public static Type flip(Type type) {
if (Type.POSITIVE.equals(type)) {
return Type.NEGATIVE;
} else {
return Type.POSITIVE;
}
}
}
Type type;
Operator operator;
private ILogical[] children;
private BoolVar[] varsAsArray;
LogOp(Operator operator, Type type, ILogical... children) {
this.type = type;
this.operator = operator;
if (children == null) {
this.children = new ILogical[0];
} else {
this.children = children;
}
}
/**
* Create a conjunction, results in true if all of its operands are true
*
* @param op operands
* @return a new logical operator
*/
public static LogOp and(ILogical... op) {
return new LogOp(Operator.AND, Type.POSITIVE, op);
}
/**
* Create a biconditional, results in true if and only if both operands are false
* or both operands are true
*
* @param a operand
* @param b operand
* @return a new logical operator
*/
public static LogOp ifOnlyIf(ILogical a, ILogical b) {
return and(implies(a, b), implies(b, a));
}
/**
* Create an implication, results in true if a is true` and b is true or a is false and c is true.
*
* @param a operand
* @param b operand
* @param c operand
* @return a new logical operator
*/
public static LogOp ifThenElse(ILogical a, ILogical b, ILogical c) {
try {
ILogical na = negate(a);
return or(and(a, b), and(na, c));
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
return null;
}
/**
* Create an implication, results in true if a is false or b is true.
*
* @param a operand
* @param b operand
* @return a new logical operator
*/
public static LogOp implies(ILogical a, ILogical b) {
try {
ILogical na = negate(a);
return or(na, b);
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
return null;
}
/**
* create a logical connection between ``b`` and ``tree``.
* @param b operand
* @param tree operand
* @return a logical operator
*/
public static LogOp reified(BoolVar b, ILogical tree) {
try {
BoolVar nb = b.not();
ILogical ntree = negate(tree);
return or(and(b, tree), and(nb, ntree));
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
return null;
}
/**
* Create a disjunction, results in true whenever one or more of its operands are true
*
* @param op operands
* @return a new logical operator
*/
public static LogOp or(ILogical... op) {
return new LogOp(Operator.OR, Type.POSITIVE, op);
}
/**
* Create an alternative denial, results in if at least one of its operands is false.
*
* @param op operands
* @return a new logical operator
*/
public static LogOp nand(ILogical... op) {
return new LogOp(Operator.AND, Type.NEGATIVE, op);
}
/**
* Create a joint denial, results in `true` if all of its operands are false.
*
* @param op operands
* @return a new logical operator
*/
public static LogOp nor(ILogical... op) {
return new LogOp(Operator.OR, Type.NEGATIVE, op);
}
/**
* Create an exclusive disjunction, results in true whenever both operands differ.
*
* @param a operand
* @param b operand
* @return a new logical operator
*/
public static LogOp xor(ILogical a, ILogical b) {
try {
ILogical na = negate(a);
ILogical nb = negate(b);
return or(and(a, nb), and(b, na));
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
return null;
}
/**
* Create the logical complement of l.
*
* @param l operand
* @return a new ILogical
* @throws CloneNotSupportedException
*/
private static ILogical negate(ILogical l) throws CloneNotSupportedException {
if (l.isLit()) {
return ((BoolVar) l).not();
} else {
LogOp n = (LogOp) l;
LogOp na = n.clone();
na.type = Type.flip(and().type);
return na;
}
}
/**
* Current tree is rooted with the logical operator op
*
* @param op operator checked
* @return true if this is op
*/
public boolean is(Operator op) {
return op.equals(operator);
}
/**
* Current tree is rooted with NOT logical operator
*
* @return true if this is NOT
*/
public boolean isNot() {
return type.equals(Type.NEGATIVE);
}
@Override
public boolean isLit() {
return false;
}
@Override
public void setNot(boolean isNot) {
throw new UnsupportedOperationException();
}
/**
* Returns the number of direct children of this
*
* @return number of children
*/
int getNbChildren() {
return children.length;
}
/**
* Check if at least one children is an OR logic tree
*
* @return true if this contains one OR logic tree
*/
boolean hasOrChild() {
for (int i = 0; i < children.length; i++) {
if (!children[i].isLit() && ((LogOp) children[i]).is(Operator.OR)) {
return true;
}
}
return false;
}
/**
* Checks if at least one children is an AND logic tree
*
* @return true if this contains one AND logic tree
*/
boolean hasAndChild() {
for (int i = 0; i < children.length; i++) {
if (!children[i].isLit() && ((LogOp) children[i]).is(Operator.AND)) {
return true;
}
}
return false;
}
/**
* Adds child to the current list of children of this
*
* @param child the logic tree to add
*/
public void addChild(ILogical child) {
ILogical[] tmp = children;
children = new ILogical[tmp.length + 1];
System.arraycopy(tmp, 0, children, 0, tmp.length);
children[tmp.length] = child;
varsAsArray = null; // force recomputation of varsArray
}
/**
* Removes child from the current list of children of this
*
* @param child the logic tree to remove
*/
public void removeChild(ILogical child) {
int i = 0;
while (i < children.length && children[i] != child) {
i++;
}
if (i == children.length) return;
ILogical[] tmp = children;
children = new ILogical[tmp.length - 1];
System.arraycopy(tmp, 0, children, 0, i);
System.arraycopy(tmp, i + 1, children, i, tmp.length - i - 1);
varsAsArray = null; // force recomputation of varsArray
}
/**
* Returns the array of children of this.
* null is a valid return value.
*
* @return an array of logic trees, null otherwise
*/
public ILogical[] getChildren() {
return children;
}
/**
* Returns the first AND logic tree within the list of children.
* null is a valid return value.
*
* @return a AND logic tree if exists, null otherwise
*/
public ILogical getAndChild() {
for (int i = 0; i < children.length; i++) {
if (!children[i].isLit() && ((LogOp) children[i]).is(Operator.AND)) {
return children[i];
}
}
return null;
}
/**
* Returns the first child within the list of children, different from child.
* null is a valid return value.
*
* @param child node to avoid
* @return the first logic tree different from child if exists, null otherwise
*/
public ILogical getChildBut(ILogical child) {
for (int i = 0; i < children.length; i++) {
if (children[i] != child) {
return children[i];
}
}
return null;
}
/**
* Flip the boolean evaluation of this (recursive).
*/
public void flip() {
type = Type.flip(type);
operator = Operator.flip(operator);
for (int i = 0; i < children.length; i++) {
if (children[i].isLit()) {
children[i] = ((BoolVar) children[i]).not();
} else {
((LogOp) children[i]).deny();
}
}
}
/**
* Flip the boolean operator of this (recursive).
*/
public void deny() {
operator = Operator.flip(operator);
for (int i = 0; i < children.length; i++) {
if (children[i].isLit()) {
children[i] = ((BoolVar) children[i]).not();
} else {
((LogOp) children[i]).deny();
}
}
}
@Override
public String toString() {
StringBuilder st = new StringBuilder();
st.append('(');
// st.append(Type.POSITIVE.equals(type) ? "(" : "not(");
String op = (Type.POSITIVE.equals(type) ? "" : "n") + (Operator.AND.equals(operator) ? "and " : "or ");
for (int i = 0; i < children.length; i++) {
ILogical child = children[i];
if (child.isLit()) {
st.append(((BoolVar) child).getName());
} else {
st.append(child);
}
st.append(" ").append(op);
}
st.replace(st.length() - (op.length() + 1), st.length(), "");
st.append(')');
return st.toString();
}
@Override
public LogOp clone() throws CloneNotSupportedException {
LogOp logOp = (LogOp) super.clone();
logOp.type = this.type;
logOp.operator = this.operator;
logOp.children = new ILogical[this.children.length];
for (int c = 0; c < children.length; c++) {
if (children[c].isLit()) {
logOp.children[c] = children[c];
} else {
logOp.children[c] = ((LogOp) children[c]).clone();
}
}
return logOp;
}
/**
* Extracts and returns the flatten array of BoolVar contained in this.
* WARNING : a variable may appear more than once, redundancy is not checked!
*
* @return array of bool variables
*/
public BoolVar[] flattenBoolVar() {
// if (varsAsArray == null) {
buildVarsArray();
// }
return varsAsArray;
}
public void cleanFlattenBoolVar() {
for (int i = 0; i < children.length; i++) {
if (!children[i].isLit()) {
((LogOp) children[i]).cleanFlattenBoolVar();
}
}
varsAsArray = null;
}
private void buildVarsArray() {
final BoolVar[][] childrenVars = new BoolVar[children.length][];
for (int i = 0; i < children.length; i++) {
if (children[i].isLit()) {
childrenVars[i] = new BoolVar[]{(BoolVar) children[i]};
} else {
childrenVars[i] = ((LogOp) children[i]).flattenBoolVar();
}
}
varsAsArray = ArrayUtils.flatten(childrenVars);
}
}