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/* Operators.java
* =========================================================================
* This file is part of the GrInvIn project - http://www.grinvin.org
*
* Copyright (C) 2005-2008 Universiteit Gent
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* A copy of the GNU General Public License can be found in the file
* LICENSE.txt provided with the source distribution of this program (see
* the META-INF directory in the source jar). This license can also be
* found on the GNU website at http://www.gnu.org/licenses/gpl.html.
*
* If you did not receive a copy of the GNU General Public License along
* with this program, contact the lead developer, or write to the Free
* Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
package org.grinvin.conjecture.engine.apengine;
import org.grinvin.expr.Compound;
import org.grinvin.expr.Expression;
import org.grinvin.expr.IntegerLiteral;
import org.grinvin.expr.StandardOperator;
public class Operators {
//
public interface Operator {
public String renderString(String[] args);
public Expression toExpression (Expression[] args);
}
//
public enum UnaryOperator implements Operator {
MINUSONE("-1") {
public double eval(double x) { return x - 1; }
public String renderString(String[] args) { return args[0] + " - 1"; }
public Expression toExpression(Expression[] args) {
return new Compound (StandardOperator.MINUS, args[0], IntegerLiteral.ONE);
}
},
PLUSONE("+1") {
public double eval(double x) { return x + 1; }
public String renderString(String[] args) { return args[0] + " + 1"; }
public Expression toExpression(Expression[] args) {
return new Compound (StandardOperator.PLUS, args[0], IntegerLiteral.ONE);
}
},
TIMESTWO("*2") {
public double eval(double x) { return x * 2; }
public String renderString(String[] args) { return args[0] + " * 2"; }
public Expression toExpression(Expression[] args) {
return new Compound (StandardOperator.TIMES, IntegerLiteral.TWO, args[0]);
}
},
DIVTWO("/2") {
public double eval(double x) { return x / 2; }
public String renderString(String[] args) { return args[0] + " / 2"; }
public Expression toExpression(Expression[] args) {
return new Compound (StandardOperator.DIV, args[0], IntegerLiteral.TWO);
}
},
SQUARED("^2") {
public double eval(double x) { return x * x; }
public String renderString(String[] args) { return args[0] + " ^ 2"; }
public Expression toExpression(Expression[] args) {
return new Compound (StandardOperator.POW, args[0], IntegerLiteral.TWO);
}
},
NEGATE("-") {
public double eval(double x) { return -x; }
public String renderString(String[] args) { return "-" + args[0]; }
public Expression toExpression(Expression[] args) {
return new Compound (StandardOperator.NEG, args[0]);
}
},
ONEOVER("1/") {
public double eval(double x) {
if(almostZero(x))
return Double.NaN;
else
return 1 / x;
}
public String renderString(String[] args) { return "1 / " + args[0]; }
public Expression toExpression(Expression[] args) {
return new Compound (StandardOperator.DIV, IntegerLiteral.ONE, args[0]);
}
};
private String name;
UnaryOperator(String name) {
this.name = name;
}
public String toString() {
return name;
}
public abstract double eval(double x);
}
//
public enum BinaryOperator implements Operator {
PLUS("+", true) {
public double eval(double x, double y) { return x + y; }
public String renderString(String[] args) { return args[0] + " + " + args[1]; }
public Expression toExpression(Expression[] args) {
return new Compound (StandardOperator.PLUS, args);
}
},
MINUS("-", false) {
public double eval(double x, double y) { return x - y; }
public String renderString(String[] args) { return args[0] + " - " + args[1]; }
public Expression toExpression(Expression[] args) {
return new Compound (StandardOperator.MINUS, args);
}
},
TIMES("*", true) {
public double eval(double x, double y) { return x * y; }
public String renderString(String[] args) { return args[0] + " * " + args[1]; }
public Expression toExpression(Expression[] args) {
return new Compound (StandardOperator.TIMES, args);
}
},
DIVIDE("/", false) {
public double eval(double x, double y) {
if(almostZero(y))
return Double.NaN;
else
return x / y;
}
public String renderString(String[] args) { return args[0] + " / " + args[1]; }
public Expression toExpression(Expression[] args) {
return new Compound (StandardOperator.DIV, args);
}
},
POWER("^", false) {
public double eval(double x, double y) { return Math.pow(x, y); }
public String renderString(String[] args) { return args[0] + " ^ " + args[1]; }
public Expression toExpression(Expression[] args) {
return new Compound (StandardOperator.POW, args);
}
};
private String name;
private boolean commutative;
BinaryOperator(String name, boolean commutative) {
this.name = name;
this.commutative = commutative;
}
public String toString() {
return name;
}
public abstract double eval(double x, double y);
public boolean isCommutative() {
return commutative;
}
}
//
public static class Invariant implements Operator {
public int number;
public Invariant(int number) {
this.number = number;
}
public String toString() {
return "I" + number;
}
public String renderString(String[] args) {
return toString();
}
public Expression toExpression(Expression[] args) {
return null; // NOT USED
}
}
//
private static boolean almostZero(double value) {
return Math.abs(value) < (1e-6);
}
}
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