org.apache.lucene.util
Class MathUtil

java.lang.Object
  org.apache.lucene.util.MathUtil

public final class MathUtil
extends Object

Math static utility methods.

Method Summary

static double	acosh(double a) Calculates inverse hyperbolic cosine of a double value.
static double	asinh(double a) Calculates inverse hyperbolic sine of a double value.
static double	atanh(double a) Calculates inverse hyperbolic tangent of a double value.
static long	gcd(long a, long b) Return the greatest common divisor of a and b, consistently with BigInteger.gcd(BigInteger).
static double	log(double base, double x) Calculates logarithm in a given base with doubles.
static int	log(long x, int base) Returns x <= 0 ? 0 : Math.floor(Math.log(x) / Math.log(base))

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

log

public static int log(long x,
                      int base)

Returns x <= 0 ? 0 : Math.floor(Math.log(x) / Math.log(base))

Parameters:

base - must be > 1

log

public static double log(double base,
                         double x)

Calculates logarithm in a given base with doubles.

gcd

public static long gcd(long a,
                       long b)

Return the greatest common divisor of a and b, consistently with BigInteger.gcd(BigInteger).

NOTE: A greatest common divisor must be positive, but 2^64 cannot be expressed as a long although it is the GCD of Long.MIN_VALUE and 0 and the GCD of Long.MIN_VALUE and Long.MIN_VALUE. So in these 2 cases, and only them, this method will return Long.MIN_VALUE.

asinh

public static double asinh(double a)

Calculates inverse hyperbolic sine of a double value.

Special cases:

• If the argument is NaN, then the result is NaN.
• If the argument is zero, then the result is a zero with the same sign as the argument.
• If the argument is infinite, then the result is infinity with the same sign as the argument.

acosh

public static double acosh(double a)

Calculates inverse hyperbolic cosine of a double value.

Special cases:

• If the argument is NaN, then the result is NaN.
• If the argument is +1, then the result is a zero.
• If the argument is positive infinity, then the result is positive infinity.
• If the argument is less than 1, then the result is NaN.

atanh

public static double atanh(double a)

Calculates inverse hyperbolic tangent of a double value.

Special cases:

• If the argument is NaN, then the result is NaN.
• If the argument is zero, then the result is a zero with the same sign as the argument.
• If the argument is +1, then the result is positive infinity.
• If the argument is -1, then the result is negative infinity.
• If the argument's absolute value is greater than 1, then the result is NaN.