// PSP Dashboard - Data Automation Tool for PSP-like processes
// Copyright (C) 1999 United States Air Force
//
// 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.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
// The author(s) may be contacted at:
// OO-ALC/TISHD
// Attn: PSP Dashboard Group
// 6137 Wardleigh Road
// Hill AFB, UT 84056-5843
//
// E-Mail POC: ken.raisor@hill.af.mil
package pspdash.data.compiler;
import pspdash.data.SimpleData;
import pspdash.data.ImmutableDoubleData;
import pspdash.data.NumberData;
class MathOperators {
private MathOperators() {}
public static final Instruction ADD = new BinaryMathOperator("+") {
protected double calc(double l, double r) { return l + r; } };
public static final Instruction SUBTRACT = new BinaryMathOperator("-") {
protected double calc(double l, double r) { return l - r; } };
public static final Instruction MULTIPLY = new BinaryMathOperator("*") {
protected double calc(double l, double r) { return l * r; } };
public static final Instruction DIVIDE = new BinaryMathOperator("/") {
protected double calc(double l, double r) {
return (r == 0 ? Double.POSITIVE_INFINITY : l / r); } };
}
/*
* Within the dashboard, we assign special meanings to two IEEE double values:
*
* o When a calculation cannot be performed because a referenced
* data element is missing or invalid, we use the double value "NaN".
*
* o When a calculation results in a divide-by-zero error, we use
* the double value "positive infinity."
*
* Because these values have special meanings, we need to perform some slight
* overrides to standard Java floating point arithmetic. For example, the
* Java language spec defines that Infinity / Infinity = NaN. That wouldn't
* make sense according to our special meanings assigned above.
*
* So the modified logic for mathematical operations is this:
*
* (1) LOGIC: Return NaN if either of the two operands is missing
* (null), not of numeric type, or NaN. EFFECT: bad or missing
* values in a calculation will cause the calculation to evaluate
* to "bad value", and this "bad value" will in turn propagate to
* any calculations it is used in.
*
* (2) LOGIC: If either operand is infinite, return positive infinity.
* EFFECT: divide-by-zero errors result in infinity, and these
* infinity values will propagate to other calculations that
* reference them.
*
* Note that special case (1) takes precedence over special case (2).
*/
class BinaryMathOperator extends BinaryOperator {
public BinaryMathOperator(String op) { super(op); }
protected SimpleData operate(SimpleData left, SimpleData right) {
if (! (left instanceof NumberData && right instanceof NumberData))
return ImmutableDoubleData.BAD_VALUE;
double leftVal = ((NumberData) left).getDouble();
double rightVal = ((NumberData) right).getDouble();
if (Double.isNaN(leftVal) || Double.isNaN(rightVal))
return ImmutableDoubleData.BAD_VALUE;
if (Double.isInfinite(leftVal) || Double.isInfinite(rightVal))
return ImmutableDoubleData.DIVIDE_BY_ZERO;
return new ImmutableDoubleData(calc(leftVal, rightVal), false, true);
}
// no-op, meant to be overwritten.
protected double calc(double left, double right) { return 0.0; }
}