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MATH-154. Added addAndCheck, mulAndCheck, and subAndCheck MathUtils methods for long integer arguments. 

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@590577 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Brent Worden 2007-10-31 07:23:01 +00:00
parent 828b70de30
commit 06da34fabc
3 changed files with 682 additions and 537 deletions
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187
src/java/org/apache/commons/math/util/MathUtils.java
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@ -68,6 +68,66 @@ public final class MathUtils {
return (int)s;
}
/**
* Add two long integers, checking for overflow.
*
* @param a an addend
* @param b an addend
* @return the sum <code>a+b</code>
* @throws ArithmeticException if the result can not be represented as an
* long
* @since 1.2
*/
public static long addAndCheck(long a, long b) {
return addAndCheck(a, b, "overflow: add");
}
/**
* Add two long integers, checking for overflow.
*
* @param a an addend
* @param b an addend
* @param msg the message to use for any thrown exception.
* @return the sum <code>a+b</code>
* @throws ArithmeticException if the result can not be represented as an
* long
* @since 1.2
*/
private static long addAndCheck(long a, long b, String msg) {
long ret;
if (a > b) {
// use symmetry to reduce boundry cases
ret = addAndCheck(b, a, msg);
} else {
// assert a <= b
if (a < 0) {
if (b < 0) {
// check for negative overflow
if (Long.MIN_VALUE - b <= a) {
ret = a + b;
} else {
throw new ArithmeticException(msg);
}
} else {
// oppisite sign addition is always safe
ret = a + b;
}
} else {
// assert a >= 0
// assert b >= 0
// check for positive overflow
if (a <= Long.MAX_VALUE - b) {
ret = a + b;
} else {
throw new ArithmeticException(msg);
}
}
}
return ret;
}
/**
* Returns an exact representation of the <a
* href="http://mathworld.wolfram.com/BinomialCoefficient.html"> Binomial
@ -117,26 +177,7 @@ public final class MathUtils {
}
return result;
}
/**
* <p>Returns the
* <a href="http://mathworld.wolfram.com/Logarithm.html">logarithm</a>
* for base <code>b</code> of <code>x</code>.
* </p>
* <p>Returns <code>NaN<code> if either argument is negative. If
* <code>base</code> is 0 and <code>x</code> is positive, 0 is returned.
* If <code>base</code> is positive and <code>x</code> is 0,
* <code>Double.NEGATIVE_INFINITY</code> is returned. If both arguments
* are 0, the result is <code>NaN</code>.</p>
*
* @param base the base of the logarithm, must be greater than 0
* @param x argument, must be greater than 0
* @return the value of the logarithm - the number y such that base^y = x.
*/
public static double log(double base, double x) {
return Math.log(x)/Math.log(base);
}
/**
* Returns a <code>double</code> representation of the <a
* href="http://mathworld.wolfram.com/BinomialCoefficient.html"> Binomial
@ -162,7 +203,7 @@ public final class MathUtils {
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"> Binomial
@ -210,7 +251,7 @@ public final class MathUtils {
return logSum;
}
/**
* Returns the <a href="http://mathworld.wolfram.com/HyperbolicCosine.html">
* hyperbolic cosine</a> of x.
@ -221,7 +262,7 @@ public final class MathUtils {
public static double cosh(double x) {
return (Math.exp(x) + Math.exp(-x)) / 2.0;
}
/**
* Returns true iff both arguments are NaN or neither is NaN and they are
* equal
@ -475,6 +516,25 @@ public final class MathUtils {
return Math.abs(mulAndCheck(a / gcd(a, b), b));
}
/**
* <p>Returns the
* <a href="http://mathworld.wolfram.com/Logarithm.html">logarithm</a>
* for base <code>b</code> of <code>x</code>.
* </p>
* <p>Returns <code>NaN<code> if either argument is negative. If
* <code>base</code> is 0 and <code>x</code> is positive, 0 is returned.
* If <code>base</code> is positive and <code>x</code> is 0,
* <code>Double.NEGATIVE_INFINITY</code> is returned. If both arguments
* are 0, the result is <code>NaN</code>.</p>
*
* @param base the base of the logarithm, must be greater than 0
* @param x argument, must be greater than 0
* @return the value of the logarithm - the number y such that base^y = x.
*/
public static double log(double base, double x) {
return Math.log(x)/Math.log(base);
}
/**
* Multiply two integers, checking for overflow.
*
@ -493,6 +553,61 @@ public final class MathUtils {
return (int)m;
}
/**
* Multiply two long integers, checking for overflow.
*
* @param a first value
* @param b second value
* @return the product <code>a * b</code>
* @throws ArithmeticException if the result can not be represented as an
* long
* @since 1.2
*/
public static long mulAndCheck(long a, long b) {
long ret;
String msg = "overflow: multiply";
if (a > b) {
// use symmetry to reduce boundry cases
ret = mulAndCheck(b, a);
} else {
if (a < 0) {
if (b < 0) {
// check for positive overflow with negative a, negative b
if (a >= Long.MAX_VALUE / b) {
ret = a * b;
} else {
throw new ArithmeticException(msg);
}
} else if (b > 0) {
// check for negative overflow with negative a, positive b
if (Long.MIN_VALUE / b <= a) {
ret = a * b;
} else {
throw new ArithmeticException(msg);
}
} else {
// assert b == 0
ret = 0;
}
} else if (a > 0) {
// assert a > 0
// assert b > 0
// check for positive overflow with positive a, positive b
if (a <= Long.MAX_VALUE / b) {
ret = a * b;
} else {
throw new ArithmeticException(msg);
}
} else {
// assert a == 0
ret = 0;
}
}
return ret;
}
/**
* Get the next machine representable number after a number, moving
* in the direction of another number.
@ -824,4 +939,30 @@ public final class MathUtils {
}
return (int)s;
}
/**
* Subtract two long integers, checking for overflow.
*
* @param a first value
* @param b second value
* @return the difference <code>a-b</code>
* @throws ArithmeticException if the result can not be represented as an
* long
* @since 1.2
*/
public static long subAndCheck(long a, long b) {
long ret;
String msg = "overflow: subtract";
if (b == Long.MIN_VALUE) {
if (a < 0) {
ret = a - b;
} else {
throw new ArithmeticException(msg);
}
} else {
// use additive inverse
ret = addAndCheck(a, -b, msg);
}
return ret;
}
}

1028
src/test/org/apache/commons/math/util/MathUtilsTest.java
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4
xdocs/changes.xml
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@ -98,6 +98,10 @@ Commons Math Release Notes</title>
<action dev="brentworden" type="update" issue="MATH-170" due-to="David J. M. Karlsen">
Added SynchronizedDescriptiveStatistics class.
</action>
<action dev="brentworden" type="update" issue="MATH-154" due-to="Remi Arntzen">
Added addAndCheck, mulAndCheck, and subAndCheck MathUtils methods for
long integer arguments.
</action>
</release>
<release version="1.1" date="2005-12-17"
description="This is a maintenance release containing bug fixes and enhancements.