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Open-source constraint solver.
/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2022, 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;
import org.chocosolver.solver.Model;
import org.chocosolver.solver.constraints.binary.*;
import org.chocosolver.solver.constraints.unary.PropEqualXC;
import org.chocosolver.solver.constraints.unary.PropGreaterOrEqualXC;
import org.chocosolver.solver.constraints.unary.PropLessOrEqualXC;
import org.chocosolver.solver.constraints.unary.PropNotEqualXC;
import org.chocosolver.solver.exception.SolverException;
import org.chocosolver.solver.variables.IntVar;
/**
* A constraint dedicated to arithmetic operations.
*
* There are three available definitions:
*
* VAR op CSTE,
* VAR op VAR,
* VAR op VAR op CSTE
*
* where VAR is a variable, CSTE a constant and op is an operator among {"=", "!=","<", ">", "<=, ">="} or{"+", "-"}.
*
* @author Charles Prud'homme
* @since 21/06/12
*/
public class Arithmetic extends Constraint {
private final Operator op1, op2; // operators.
// required visibility to allow exportation
protected final int cste;
private final IntVar[] vars;
private static boolean isOperation(Operator operator) {
return operator.equals(Operator.PL) || operator.equals(Operator.MN);
}
// for JSON
@SuppressWarnings("WeakerAccess")
protected Arithmetic(String name, IntVar[] vars, Operator op1, Operator op2, int cste, Propagator prop){
super(name, prop);
this.vars = vars;
this.op1 = op1;
this.op2 = op2;
this.cste = cste;
}
Arithmetic(IntVar var, Operator op, int cste) {
this(ConstraintsName.ARITHM, new IntVar[]{var}, op, Operator.NONE, cste, createProp(var,op,cste));
}
private static Propagator createProp(IntVar var, Operator op, int cste) {
switch (op) {
case EQ: // X = C
return new PropEqualXC(var, cste);
case NQ: // X =/= C
return new PropNotEqualXC(var, cste);
case GE: // X >= C
return new PropGreaterOrEqualXC(var, cste);
case GT: // X > C --> X >= C + 1
return new PropGreaterOrEqualXC(var, cste + 1);
case LE: // X <= C
return new PropLessOrEqualXC(var, cste);
case LT: // X < C --> X <= C - 1
return new PropLessOrEqualXC(var, cste - 1);
default:
throw new SolverException("Incorrect formula; operator should be one of those:{=, !=, >=, >, <=, <}");
}
}
Arithmetic(IntVar var1, Operator op, IntVar var2) {
this(ConstraintsName.ARITHM, new IntVar[]{var1,var2}, op, Operator.PL, 0, createProp(var1,op,var2));
}
private static Propagator createProp(IntVar var1, Operator op, IntVar var2) {
switch (op) {
case EQ: // X = Y
return new PropEqualX_Y(var1, var2);
case NQ: // X =/= Y
return new PropNotEqualX_Y(var1, var2);
case GE: // X >= Y
return new PropGreaterOrEqualX_Y(new IntVar[]{var1,var2});
case GT: // X > Y --> X >= Y + 1
return new PropGreaterOrEqualX_YC(new IntVar[]{var1,var2}, 1);
case LE: // X <= Y --> Y >= X
return new PropGreaterOrEqualX_Y(new IntVar[]{var2, var1});
case LT: // X < Y --> Y >= X + 1
return new PropGreaterOrEqualX_YC(new IntVar[]{var2, var1}, 1);
default:
throw new SolverException("Incorrect formula; operator should be one of those:{=, !=, >=, >, <=, <}");
}
}
Arithmetic(IntVar var1, Operator op1, IntVar var2, Operator op2, int cste) {
this(ConstraintsName.ARITHM, new IntVar[]{var1,var2}, op1, op2, cste, createProp(var1,op1,var2,op2,cste));
if (isOperation(op1) == isOperation(op2)) {
throw new SolverException("Incorrect formula; operators must be different!");
}
}
private static Propagator createProp(IntVar var1, Operator op1, IntVar var2, Operator op2, int cste) {
if(op1==null)throw new UnsupportedOperationException();
if(op2==null)throw new UnsupportedOperationException();
if (isOperation(op1) == isOperation(op2)) {
throw new SolverException("Incorrect formula; operators must be different!");
}
IntVar[] vars = new IntVar[]{var1,var2};
if (op1 == Operator.PL) {
switch (op2) {
case EQ: // X+Y = C
return new PropEqualXY_C(vars, cste);
case NQ: // X+Y != C
return new PropNotEqualXY_C(vars, cste);
case GE: // X+Y >= C
return new PropGreaterOrEqualXY_C(vars, cste);
case GT: // X+Y > C --> X+Y >= C+1
return new PropGreaterOrEqualXY_C(vars, cste + 1);
case LE: // X+Y <= C
return new PropLessOrEqualXY_C(vars, cste);
case LT: // X+Y < C --> X+Y <= C-1
return new PropLessOrEqualXY_C(vars, cste - 1);
default:
throw new SolverException("Incorrect formula; operator should be one of those:{=, !=, >=, >, <=, <}");
}
} else{
Operator op = op2;
if (op1 != Operator.MN) {
cste *= (op2 == Operator.PL ? 1 : -1);
op = op1;
}
switch (op) {
case EQ: // X-Y = C --> X = Y+C
if(cste == 0)return new PropEqualX_Y(vars[0], vars[1]);
return new PropEqualX_YC(vars, cste);
case NQ: // X-Y != C --> X != Y+C
if(cste == 0)return new PropNotEqualX_Y(vars[0], vars[1]);
return new PropNotEqualX_YC(vars, cste);
case GE: // X-Y >= C --> X >= Y+C
if(cste == 0)return new PropGreaterOrEqualX_Y(vars);
return new PropGreaterOrEqualX_YC(vars, cste);
case GT: // X-Y > C --> X >= Y+C+1
if(cste == -1)return new PropGreaterOrEqualX_Y(vars);
return new PropGreaterOrEqualX_YC(vars, cste + 1);
case LE:// X-Y <= C --> Y >= X-C
if(cste == 0)return new PropGreaterOrEqualX_Y(new IntVar[]{var2, var1});
return new PropGreaterOrEqualX_YC(new IntVar[]{var2, var1}, -cste);
case LT:// X-Y < C --> Y >= X-C+1
if(cste == 1) return new PropGreaterOrEqualX_Y(new IntVar[]{var2, var1});
return new PropGreaterOrEqualX_YC(new IntVar[]{var2, var1}, -cste + 1);
default:
throw new SolverException("Incorrect formula; operator should be one of those:{=, !=, >=, >, <=, <}");
}
}
}
@Override
public Constraint makeOpposite(){
Model model = vars[0].getModel();
if(vars.length==1){
return model.arithm(vars[0],Operator.getOpposite(op1).toString(),cste);
}else{
assert vars.length==2;
if(op1==Operator.PL || op1==Operator.MN){
return model.arithm(vars[0],op1.toString(),vars[1],Operator.getOpposite(op2).toString(),cste);
}else{
return model.arithm(vars[0],Operator.getOpposite(op1).toString(),vars[1],op2.toString(),cste);
}
}
}
}