Mega Code Archive
Floating Point Arithmetic
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/********************************************************************
Copyright (c) 1996 Artima Software Company. All Rights Reserved.
* Permission to use, copy, modify, and distribute this software
* and its documentation for EVALUATION purposes only
* is hereby granted provided that this copyright notice
* appears in all copies. "Evaluation purposes" are any uses which
* do not constitute the sale, sharing, or redistribution of this
* software with or to any other persons in any medium.
*
* ARTIMA SOFTWARE COMPANY MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT
* THE SUITABILITY OF THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING
* BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. ARTIMA SOFTWARE COMPANY
* SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF
* USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
PROJECT: JavaWorld
MODULE: Under The Hood
FILE: ExposedFloat.java
AUTHOR: Bill Venners, August 1996
DESCRIPTION:
This file contains all the code for the Floating Point Viewer
applet, named Exposed Float, that accompanies the Under The Hood article titled,
"Floating Point Arithmetic".
As I developed this applet I had every class in a separate file. I combined
them in one file here to make it easier to download.
*********************************************************************/
import java.awt.*;
import java.applet.*;
public class ExposedFloat extends Applet {
private Label binaryField;
private Label signField;
private Label exponentField;
private Label mantissaField;
private Label hexField;
private Label base2Field;
private Label base10Field;
private float value;
private final String titleString = "EXPOSED FLOAT";
private final String binaryString = "binary";
private final String signString = "sign";
private final String exponentString = "exponent";
private final String mantissaString = "mantissa";
private final String hexString = "hex";
private final String base10String = "radix 10";
private final String base2String = "radix 2";
private final String incrementButtonString = "++";
private final String decrementButtonString = "--";
private final String multByZeroButtonString = "*=(0)";
private final String piButtonString = "Pi";
private final String positiveInfinityButtonString = "+Inf";
private final String negativeInfinityButtonString = "-Inf";
private final String maximumButtonString = "Max";
private final String minimumButtonString = "Min";
private final String notANumberButtonString = "NaN";
private final String changeSignButtonString = "*=(-1)";
private final String doubleButtonString = "*=(2)";
private final String halveButtonString = "/=(2)";
private final String notANumberString = "Not A Number";
private final String positiveInfinityString = "+Infinity";
private final String negativeInfinityString = "-Infinity";
Button maximumButton = new Button(maximumButtonString);
Button minimumButton = new Button(minimumButtonString);
Button positiveInfinityButton = new Button(positiveInfinityButtonString);
Button negativeInfinityButton = new Button(negativeInfinityButtonString);
Button piButton = new Button(piButtonString);
Button notANumberButton = new Button(notANumberButtonString);
public void init() {
Panel buttonPanel = new PanelWithInsets(0, 0, 0, 0);
buttonPanel.setLayout(new GridLayout(6, 2, 5, 5));
buttonPanel.add(maximumButton);
buttonPanel.add(minimumButton);
buttonPanel.add(positiveInfinityButton);
buttonPanel.add(negativeInfinityButton);
buttonPanel.add(piButton);
buttonPanel.add(notANumberButton);
buttonPanel.add(new Button(multByZeroButtonString));
buttonPanel.add(new Button(changeSignButtonString));
buttonPanel.add(new Button(doubleButtonString));
buttonPanel.add(new Button(halveButtonString));
buttonPanel.add(new RepeaterButton(incrementButtonString));
buttonPanel.add(new RepeaterButton(decrementButtonString));
binaryField = new Label("00000000000000000000000000000000");
signField = new Label("0");
exponentField = new Label("00000000");
mantissaField = new Label("000000000000000000000000");
hexField = new Label("00000000");
base2Field = new Label("0");
base10Field = new Label("0");
Font fieldFont = new Font("TimesRoman", Font.PLAIN, 12);
binaryField.setFont(fieldFont);
signField.setFont(fieldFont);
exponentField.setFont(fieldFont);
mantissaField.setFont(fieldFont);
hexField.setFont(fieldFont);
base2Field.setFont(fieldFont);
base10Field.setFont(fieldFont);
Panel numberPanel = new Panel();
numberPanel.setBackground(Color.white);
numberPanel.setLayout(new GridLayout(7, 1));
numberPanel.add(signField);
numberPanel.add(exponentField);
numberPanel.add(mantissaField);
Panel binaryPanel = new Panel();
binaryPanel.setLayout(new BorderLayout());
binaryPanel.add("Center", binaryField);
numberPanel.add(binaryPanel);
Panel hexPanel = new Panel();
hexPanel.setLayout(new BorderLayout());
hexPanel.add("Center", hexField);
numberPanel.add(hexPanel);
numberPanel.add(base2Field);
numberPanel.add(base10Field);
Panel labelPanel = new Panel();
labelPanel.setBackground(Color.white);
labelPanel.setLayout(new GridLayout(7, 1));
Font labelFont = new Font("Helvetica", Font.ITALIC, 11);
Label label = new Label(signString, Label.CENTER);
label.setFont(labelFont);
labelPanel.add(label);
label = new Label(exponentString, Label.CENTER);
label.setFont(labelFont);
labelPanel.add(label);
label = new Label(mantissaString, Label.CENTER);
label.setFont(labelFont);
labelPanel.add(label);
label = new Label(binaryString, Label.CENTER);
label.setFont(labelFont);
labelPanel.add(label);
label = new Label(hexString, Label.CENTER);
label.setFont(labelFont);
labelPanel.add(label);
label = new Label(base2String, Label.CENTER);
label.setFont(labelFont);
labelPanel.add(label);
label = new Label(base10String, Label.CENTER);
label.setFont(labelFont);
labelPanel.add(label);
Panel dataPanel = new Panel();
dataPanel.setLayout(new BorderLayout());
dataPanel.add("West", labelPanel);
dataPanel.add("Center", numberPanel);
ColoredLabel title = new ColoredLabel(titleString, Label.CENTER, Color.cyan);
title.setFont(new Font("Helvetica", Font.BOLD, 12));
setBackground(Color.green);
setLayout(new BorderLayout(5, 5));
add("North", title);
add("West", buttonPanel);
add("Center", dataPanel);
}
public boolean action(Event evt, Object arg) {
if (evt.target instanceof Button) {
String bname = (String) arg;
if (bname.equals(incrementButtonString)) {
++value;
}
else if (bname.equals(decrementButtonString)) {
--value;
}
else if (bname.equals(multByZeroButtonString)) {
value *= (float) 0.0;
}
else if (bname.equals(piButtonString)) {
value = (float) Math.PI;
}
else if (bname.equals(positiveInfinityButtonString)) {
value = Float.POSITIVE_INFINITY;
}
else if (bname.equals(negativeInfinityButtonString)) {
value = Float.NEGATIVE_INFINITY;
}
else if (bname.equals(maximumButtonString)) {
value = Float.MAX_VALUE;
}
else if (bname.equals(minimumButtonString)) {
value = Float.MIN_VALUE;
}
else if (bname.equals(notANumberButtonString)) {
value = Float.NaN;
}
else if (bname.equals(changeSignButtonString)) {
value *= -1.0;
}
else if (bname.equals(doubleButtonString)) {
value *= 2.0;
}
else if (bname.equals(halveButtonString)) {
value /= 2.0;
}
updateNumberFields();
enableDisableButton(maximumButton, Float.MAX_VALUE);
enableDisableButton(minimumButton, Float.MIN_VALUE);
enableDisableButton(positiveInfinityButton, Float.POSITIVE_INFINITY);
enableDisableButton(negativeInfinityButton, Float.NEGATIVE_INFINITY);
enableDisableButton(piButton, (float) Math.PI);
enableDisableButton(notANumberButton, Float.NaN);
if (!notANumberButton.isEnabled()) {
if (!Float.isNaN(value)) {
notANumberButton.enable();
}
} else if (Float.isNaN(value)) {
notANumberButton.disable();
}
}
return true;
}
void enableDisableButton(Button b, float val) {
if (!b.isEnabled()) {
if (value != val) {
b.enable();
}
} else if (value == val) {
b.disable();
}
}
void updateNumberFields() {
int intBits = Float.floatToIntBits(value);
if (Float.isNaN(value)) {
base10Field.setText(notANumberString);
}
else if (Float.isInfinite(value)) {
if ((intBits >>> 31) == 1) {
// This is a negative infinity
base10Field.setText(negativeInfinityString);
}
else {
// This is a positive infinity
base10Field.setText(positiveInfinityString);
}
}
else if (intBits == (int) 0x80000000) {
base10Field.setText("-0");
}
else {
base10Field.setText(Float.toString(value));
}
int v = intBits;
StringBuffer buf = new StringBuffer();
for (int i = 0; i < 8; ++i) {
// Get lowest bit
int remainder = v & 0xf;
// Convert bit to a character and insert it into the beginning of the string
switch (remainder) {
case 0:
buf.insert(0, "0");
break;
case 1:
buf.insert(0, "1");
break;
case 2:
buf.insert(0, "2");
break;
case 3:
buf.insert(0, "3");
break;
case 4:
buf.insert(0, "4");
break;
case 5:
buf.insert(0, "5");
break;
case 6:
buf.insert(0, "6");
break;
case 7:
buf.insert(0, "7");
break;
case 8:
buf.insert(0, "8");
break;
case 9:
buf.insert(0, "9");
break;
case 10:
buf.insert(0, "a");
break;
case 11:
buf.insert(0, "b");
break;
case 12:
buf.insert(0, "c");
break;
case 13:
buf.insert(0, "d");
break;
case 14:
buf.insert(0, "e");
break;
case 15:
buf.insert(0, "f");
break;
}
// Shift the int to the right one bit
v >>>= 4;
}
hexField.setText(buf.toString());
v = intBits;
buf.setLength(0);
for (int i = 0; i < 32; ++i) {
// Get lowest bit
int remainder = v & 0x1;
// Convert bit to a character and insert it into the beginning of the string
if (remainder == 0) {
buf.insert(0, "0");
}
else {
buf.insert(0, "1");
}
// Shift the int to the right one bit
v >>>= 1;
}
binaryField.setText(buf.toString());
if (intBits < 0) {
signField.setText("1");
}
else {
signField.setText("0");
}
v = intBits >> 23;
buf.setLength(0);
for (int i = 0; i < 8; ++i) {
// Get lowest bit
int remainder = v & 0x1;
// Convert bit to a character and insert it into the beginning of the string
if (remainder == 0) {
buf.insert(0, "0");
}
else {
buf.insert(0, "1");
}
// Shift the int to the right one bit
v >>>= 1;
}
exponentField.setText(buf.toString());
// Do the mantissa
v = intBits;
buf.setLength(0);
for (int i = 0; i < 23; ++i) {
// Get lowest bit
int remainder = v & 0x1;
// Convert bit to a character and insert it into the beginning of the string
if (remainder == 0) {
buf.insert(0, "0");
}
else {
buf.insert(0, "1");
}
// Shift the int to the right one bit
v >>>= 1;
}
if (((intBits >> 23) & 0xff) == 0) {
// This is a denormalized number, first bit is 0
buf.insert(0, "0");
}
else {
// This is a normalized number, first bit is 1
buf.insert(0, "1");
}
mantissaField.setText(buf.toString());
// Print out a denormalized base 2 version.
buf.setLength(0);
if (Float.isNaN(value)) {
buf.append(notANumberString);
}
else if (Float.isInfinite(value)) {
if ((intBits >>> 31) == 1) {
// This is a negative infinity
buf.append(negativeInfinityString);
}
else {
// This is a positive infinity
buf.append(positiveInfinityString);
}
}
else {
if ((intBits >>> 31) == 1) {
// This is a negative number
buf.append("-");
}
// Convert mantissa to int.
v = (intBits & 0x007fffff);
if (((intBits >> 23) & 0xff) != 0) {
// Set bit 23 if the number is normalized
v |= 0x00800000;
}
buf.append(v);
// print out the exponent
v = (intBits >> 23) & 0xff;
if (v != 150 && intBits != 0 && intBits != (int) 0x80000000) {
if (v != 0) {
// regular normalized number
buf.append("e" + (v - 150));
}
else {
// denormalized number
buf.append("e-149");
}
}
}
base2Field.setText(buf.toString());
}
public Insets insets() {
return new Insets(5, 5, 5, 5);
}
}
// I used this class because I can't seem to set the background color of
// a label. I only want a label, but I want the backgound to be gray.
class ColoredLabel extends Panel {
private Label theLabel;
ColoredLabel(String label, int alignment, Color color) {
setLayout(new GridLayout(1,1));
setBackground(color);
theLabel = new Label(label, alignment);
add(theLabel);
}
public void setLabelText(String s) {
theLabel.setText(s);
}
public Insets insets() {
return new Insets(0, 0, 0, 0);
}
}
class GrayButton extends Button {
GrayButton(String label) {
super(label);
setBackground(Color.lightGray);
}
}
class PanelWithInsets extends Panel {
private int top;
private int left;
private int bottom;
private int right;
PanelWithInsets(int t, int l, int b, int r) {
top = t;
left = l;
bottom = b;
right = r;
}
PanelWithInsets() {
top = 5;
left = 5;
bottom = 5;
right = 5;
}
public Insets insets() {
return new Insets(top, left, bottom, right);
}
}
class RepeaterButton extends GrayButton {
RepeaterButton(String label) {
super(label);
}
}
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