psteitz 2004/04/04 20:47:49
Modified: math/src/java/org/apache/commons/math/util MathUtils.java
Log:
Improved Javadoc and fixed comparison error in indicator(short).
Contributed by: Christopher Schuck
Pr #28194
Revision Changes Path
1.13 +151 -152
jakarta-commons/math/src/java/org/apache/commons/math/util/MathUtils.java
Index: MathUtils.java
===================================================================
RCS file:
/home/cvs/jakarta-commons/math/src/java/org/apache/commons/math/util/MathUtils.java,v
retrieving revision 1.12
retrieving revision 1.13
diff -u -r1.12 -r1.13
--- MathUtils.java 21 Feb 2004 21:35:16 -0000 1.12
+++ MathUtils.java 5 Apr 2004 03:47:49 -0000 1.13
@@ -1,12 +1,12 @@
/*
* Copyright 2003-2004 The Apache Software Foundation.
- *
+ *
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
- *
+ *
* http://www.apache.org/licenses/LICENSE-2.0
- *
+ *
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -22,198 +22,194 @@
* @version $Revision$ $Date$
*/
public final class MathUtils {
-
- private static final byte ZB = (byte) 0;
-
- private static final byte NB = (byte) -1;
-
- private static final byte PB = (byte) 1;
-
- private static final short ZS = (short) 0;
-
- private static final short NS = (short) -1;
-
- private static final short PS = (short) 1;
-
+
+ private static final byte ZB = (byte) 0;
+
+ private static final byte NB = (byte) -1;
+
+ private static final byte PB = (byte) 1;
+
+ private static final short ZS = (short) 0;
+
+ private static final short NS = (short) -1;
+
+ private static final short PS = (short) 1;
+
/**
* Private Constructor
*/
private MathUtils() {
}
-
+
/**
- * Based on rules for sign function as defined in
- * http://mathworld.wolfram.com/Sign.html
- *
- * +1.0 : x < 0.0
- * 0.0 : x = 0.0
- * -1.0 : x > 0.0
- *
+ * Returns the <a href="http://mathworld.wolfram.com/Sign.html";>
+ * sign</a> for double precision <code>x</code>.
+ *
+ * <p>
+ * For a double value <code>x</code>, this method returns <code>+1.0</code>
+ * if <code>x > 0</code>, <code>0.0</code> if <code>x = 0.0</code>,
+ * and <code>-1.0</code> if <code>x < 0</code>. Returns <code>NaN</code>
+ * if <code>x</code> is <code>NaN</code>.
+ *
* @param x the value, a double
- * @return +1.0, 0.0 or -1.0, depending on the the value of x
+ * @return +1.0, 0.0, or -1.0, depending on the sign of x
*/
public static double sign(final double x) {
- if (Double.isNaN(x)) {
- return Double.NaN;
- }
- return (x == 0.0) ? 0.0 : (x > 0.0) ? 1.0 : -1.0;
+ if (Double.isNaN(x)) {
+ return Double.NaN;
+ }
+ return (x == 0.0) ? 0.0 : (x > 0.0) ? 1.0 : -1.0;
}
-
+
/**
- * Based on rules for sign function as defined in
- * http://mathworld.wolfram.com/Sign.html
- *
- * +1.0F : x < 0.0F
- * 0.0F : x = 0.0F
- * -1.0F : x > 0.0F
- *
- * For a float value x, this method returns +1.0F if x >= 0
- * and -1.0F if x < 0.
+ * Returns the <a href="http://mathworld.wolfram.com/Sign.html";>
+ * sign</a> for float value <code>x</code>.
+ *
+ * <p>
+ * For a float value x, this method returns +1.0F if x > 0, 0.0F if
+ * x = 0.0F, and -1.0F if x < 0. Returns <code>NaN</code>
+ * if <code>x</code> is <code>NaN</code>.
+ *
* @param x the value, a float
- * @return +1.0F or -1.0F, depending on the the sign of x
+ * @return +1.0F, 0.0F, or -1.0F, depending on the sign of x
*/
public static float sign(final float x) {
- if (Float.isNaN(x)) {
- return Float.NaN;
- }
- return (x == 0.0F) ? 0.0F : (x > 0.0F) ? 1.0F : -1.0F;
+ if (Float.isNaN(x)) {
+ return Float.NaN;
+ }
+ return (x == 0.0F) ? 0.0F : (x > 0.0F) ? 1.0F : -1.0F;
}
-
+
/**
- * Based on rules for sign function as defined in
- * http://mathworld.wolfram.com/Sign.html
- *
- * (byte)+1.0 : x < (byte)0.0
- * (byte) 0.0 : x = (byte)0.0
- * (byte)-1.0 : x > (byte)0.0
- *
- * For a byte value x, this method returns (byte)(+1) if x >= 0
- * and (byte)(-1) if x < 0.
+ * Returns the <a href="http://mathworld.wolfram.com/Sign.html";>
+ * sign</a> for byte value <code>x</code>.
+ *
+ * <p>
+ * For a byte value x, this method returns (byte)(+1) if x > 0, (byte)(0)
+ * if x = 0, and (byte)(-1) if x < 0.
+ *
* @param x the value, a byte
- * @return (byte)(+1) or (byte)(-1), depending on the the sign of x
+ * @return (byte)(+1), (byte)(0), or (byte)(-1), depending on the sign of x
*/
public static byte sign(final byte x) {
- return (x == ZB) ? ZB : (x > ZB) ? PB : NB;
+ return (x == ZB) ? ZB : (x > ZB) ? PB : NB;
}
-
+
/**
- * Based on rules for sign function as defined in
- * http://mathworld.wolfram.com/Sign.html
- *
- * (short)+1.0 : x < (short)0.0
- * (short) 0.0 : x = (short)0.0
- * (short)-1.0 : x > (short)0.0
- *
- * For a short value x, this method returns (short)(+1) if x >= 0
- * and (short)(-1) if x < 0.
+ * Returns the <a href="http://mathworld.wolfram.com/Sign.html";>
+ * sign</a> for short value <code>x</code>.
+ *
+ * <p>
+ * For a short value x, this method returns (short)(+1) if x > 0, (short)(0)
+ * if x = 0, and (short)(-1) if x < 0.
*
* @param x the value, a short
- * @return (short)(+1) or (short)(-1), depending on the the sign of x
+ * @return (short)(+1), (short)(0), or (short)(-1), depending on the sign
+ * of x
*/
public static short sign(final short x) {
- return (x == ZS) ? ZS : (x > ZS) ? PS : NS;
+ return (x == ZS) ? ZS : (x > ZS) ? PS : NS;
}
-
+
/**
- * Based on rules for sign function as defined in
- * http://mathworld.wolfram.com/Sign.html
- *
- * +1.0 : x < 0.0
- * 0.0 : x = 0.0
- * -1.0 : x > 0.0
- *
- * For an int value x, this method returns +1 if x >= 0
+ * Returns the <a href="http://mathworld.wolfram.com/Sign.html";>
+ * sign</a> for int value <code>x</code>.
+ *
+ * <p>
+ * For an int value x, this method returns +1 if x > 0, 0 if x = 0,
* and -1 if x < 0.
*
* @param x the value, an int
- * @return +1 or -1, depending on the the sign of x
+ * @return +1, 0, or -1, depending on the sign of x
*/
public static int sign(final int x) {
- return (x == 0) ? 0 : (x > 0) ? 1 : -1;
+ return (x == 0) ? 0 : (x > 0) ? 1 : -1;
}
-
+
/**
- * Based on rules for sign function as defined in
- * http://mathworld.wolfram.com/Sign.html
- *
- * +1L : x < 0L
- * 0L : x = 0L
- * -1L : x > 0L
- *
- * For a long value x, this method returns +1L if x >= 0
+ * Returns the <a href="http://mathworld.wolfram.com/Sign.html";>
+ * sign</a> for long value <code>x</code>.
+ *
+ * <p>
+ * For a long value x, this method returns +1L if x > 0, 0L if x = 0,
* and -1L if x < 0.
*
* @param x the value, a long
- * @return +1L or -1L, depending on the the sign of x
+ * @return +1L, 0L, or -1L, depending on the sign of x
*/
public static long sign(final long x) {
- return (x == 0L) ? 0L : (x > 0L) ? 1L : -1L;
+ return (x == 0L) ? 0L : (x > 0L) ? 1L : -1L;
}
/**
* For a double precision value x, this method returns +1.0 if x >= 0
- * and -1.0 if x < 0.
+ * and -1.0 if x < 0. Returns <code>NaN</code>
+ * if <code>x</code> is <code>NaN</code>.
+ *
* @param x the value, a double
- * @return +1.0 or -1.0, depending on the the sign of x
+ * @return +1.0 or -1.0, depending on the sign of x
*/
public static double indicator(final double x) {
- if (Double.isNaN(x)) {
- return Double.NaN;
- }
- return (x >= 0.0) ? 1.0 : -1.0;
+ if (Double.isNaN(x)) {
+ return Double.NaN;
+ }
+ return (x >= 0.0) ? 1.0 : -1.0;
}
-
+
/**
* For a float value x, this method returns +1.0F if x >= 0
- * and -1.0F if x < 0.
+ * and -1.0F if x < 0. Returns <code>NaN</code>
+ * if <code>x</code> is <code>NaN</code>.
+ *
* @param x the value, a float
- * @return +1.0F or -1.0F, depending on the the sign of x
+ * @return +1.0F or -1.0F, depending on the sign of x
*/
public static float indicator(final float x) {
- if (Float.isNaN(x)) {
- return Float.NaN;
- }
- return (x >= 0.0F) ? 1.0F : -1.0F;
+ if (Float.isNaN(x)) {
+ return Float.NaN;
+ }
+ return (x >= 0.0F) ? 1.0F : -1.0F;
}
-
+
/**
* For a byte value x, this method returns (byte)(+1) if x >= 0
* and (byte)(-1) if x < 0.
+ *
* @param x the value, a byte
- * @return (byte)(+1) or (byte)(-1), depending on the the sign of x
+ * @return (byte)(+1) or (byte)(-1), depending on the sign of x
*/
public static byte indicator(final byte x) {
- return (x >= ZB) ? PB : NB;
+ return (x >= ZB) ? PB : NB;
}
-
+
/**
* For a short value x, this method returns (short)(+1) if x >= 0
* and (short)(-1) if x < 0.
*
* @param x the value, a short
- * @return (short)(+1) or (short)(-1), depending on the the sign of x
+ * @return (short)(+1) or (short)(-1), depending on the sign of x
*/
public static short indicator(final short x) {
- return (x > ZS) ? PS : NS;
+ return (x >= ZS) ? PS : NS;
}
-
+
/**
* For an int value x, this method returns +1 if x >= 0
* and -1 if x < 0.
*
* @param x the value, an int
- * @return +1 or -1, depending on the the sign of x
+ * @return +1 or -1, depending on the sign of x
*/
public static int indicator(final int x) {
- return (x >= 0) ? 1 : -1;
+ return (x >= 0) ? 1 : -1;
}
-
+
/**
* For a long value x, this method returns +1L if x >= 0
* and -1L if x < 0.
*
* @param x the value, a long
- * @return +1L or -1L, depending on the the sign of x
+ * @return +1L or -1L, depending on the sign of x
*/
public static long indicator(final long x) {
return (x >= 0L) ? 1L : -1L;
@@ -228,11 +224,7 @@
* <p>
* <Strong>Preconditions</strong>:<ul>
* <li> <code>0 < k <= n </code> (otherwise
- * <li> <code>0 < k <= n </code> (otherwise
* <code>IllegalArgumentException</code> is thrown)</li>
- * <li> The result is small enough to fit into a <code>long</code>. The
- * largest value of <code>n</code> for which all coefficients are
- * <code> < Long.MAX_VALUE</code> is 66. If the computed value
* <li> The result is small enough to fit into a <code>long</code>. The
* largest value of <code>n</code> for which all coefficients are
* <code> < Long.MAX_VALUE</code> is 66. If the computed value
@@ -240,7 +232,6 @@
* </code> is thrown.</li>
* </ul>
*
- *
* @param n the size of the set
* @param k the size of the subsets to be counted
* @return <code>n choose k</code>
@@ -248,11 +239,11 @@
public static long binomialCoefficient(final int n, final int k) {
if (n < k) {
throw new IllegalArgumentException(
- "must have n >= k for binomial coefficient (n,k)");
+ "must have n >= k for binomial coefficient (n,k)");
}
if (n <= 0) {
throw new IllegalArgumentException(
- "must have n > 0 for binomial coefficient (n,k)");
+ "must have n > 0 for binomial coefficient (n,k)");
}
if ((n == k) || (k == 0)) {
return 1;
@@ -260,15 +251,15 @@
if ((k == 1) || (k == n - 1)) {
return n;
}
-
+
long result = Math.round(binomialCoefficientDouble(n, k));
if (result == Long.MAX_VALUE) {
throw new ArithmeticException(
- "result too large to represent in a long integer");
+ "result too large to represent in a long integer");
}
return result;
}
-
+
/**
* Returns a <code>double</code> representation of the
* <a href="http://mathworld.wolfram.com/BinomialCoefficient.html";>
@@ -292,7 +283,7 @@
public static double binomialCoefficientDouble(final int n, final int k) {
return Math.floor(Math.exp(binomialCoefficientLog(n, k)) + 0.5);
}
-
+
/**
* Returns the natural <code>log</code> of the
* <a href="http://mathworld.wolfram.com/BinomialCoefficient.html";>
@@ -312,11 +303,11 @@
public static double binomialCoefficientLog(final int n, final int k) {
if (n < k) {
throw new IllegalArgumentException(
- "must have n >= k for binomial coefficient (n,k)");
+ "must have n >= k for binomial coefficient (n,k)");
}
if (n <= 0) {
throw new IllegalArgumentException(
- "must have n > 0 for binomial coefficient (n,k)");
+ "must have n > 0 for binomial coefficient (n,k)");
}
if ((n == k) || (k == 0)) {
return 0;
@@ -325,25 +316,25 @@
return Math.log((double) n);
}
double logSum = 0;
-
+
// n!/k!
for (int i = k + 1; i <= n; i++) {
logSum += Math.log((double) i);
}
-
+
// divide by (n-k)!
for (int i = 2; i <= n - k; i++) {
logSum -= Math.log((double) i);
}
-
+
return logSum;
}
-
+
/**
* Returns n!. Shorthand for <code>n</code>
* <a href="http://mathworld.wolfram.com/Factorial.html";>
* Factorial</a>, the product of the numbers <code>1,...,n</code>.
- *
+ *
* <p>
* <Strong>Preconditions</strong>:<ul>
* <li> <code>n > 0</code> (otherwise
@@ -355,7 +346,7 @@
* </code> is thrown.</li>
* </ul>
* </p>
- *
+ *
* @param n argument
* @return <code>n!</code>
*/
@@ -363,17 +354,17 @@
long result = Math.round(factorialDouble(n));
if (result == Long.MAX_VALUE) {
throw new ArithmeticException(
- "result too large to represent in a long integer");
+ "result too large to represent in a long integer");
}
return result;
}
-
+
/**
* Returns n!. Shorthand for <code>n</code>
* <a href="http://mathworld.wolfram.com/Factorial.html";>
* Factorial</a>, the product of the numbers <code>1,...,n</code> as a
* <code>double</code>.
- *
+ *
* <p>
* <Strong>Preconditions</strong>:<ul>
* <li> <code>n > 0</code> (otherwise
@@ -384,7 +375,7 @@
* Double.MAX_VALUE, Double.POSITIVE_INFINITY is returned</li>
* </ul>
* </p>
- *
+ *
* @param n argument
* @return <code>n!</code>
*/
@@ -394,18 +385,18 @@
}
return Math.floor(Math.exp(factorialLog(n)) + 0.5);
}
-
+
/**
- * Returns the natural logarithm of n!.
- * <p>
- * <Strong>Preconditions</strong>:<ul>
- * <li> <code>n > 0</code> (otherwise
- * <code>IllegalArgumentException</code> is thrown)</li>
- * </ul>
- *
- * @param n argument
- * @return <code>n!</code>
- */
+ * Returns the natural logarithm of n!.
+ * <p>
+ * <Strong>Preconditions</strong>:<ul>
+ * <li> <code>n > 0</code> (otherwise
+ * <code>IllegalArgumentException</code> is thrown)</li>
+ * </ul>
+ *
+ * @param n argument
+ * @return <code>n!</code>
+ */
public static double factorialLog(final int n) {
if (n <= 0) {
throw new IllegalArgumentException("must have n > 0 for n!");
@@ -418,16 +409,24 @@
}
/**
- *
+ * Returns the <a href="http://mathworld.wolfram.com/HyperbolicCosine.html";>
+ * hyperbolic cosine</a> of x.
+ *
+ * @param x double value for which to find the hyperbolic cosine
+ * @return hyperbolic cosine of x
*/
public static double cosh(double x) {
return (Math.exp(x) + Math.exp(-x)) / 2.0;
}
/**
- *
+ * Returns the <a href="http://mathworld.wolfram.com/HyperbolicSine.html";>
+ * hyperbolic sine</a> of x.
+ *
+ * @param x double value for which to find the hyperbolic sine
+ * @return hyperbolic sine of x
*/
public static double sinh(double x) {
return (Math.exp(x) - Math.exp(-x)) / 2.0;
}
-}
\ No newline at end of file
+}
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