org.apache.lucene.util
Class SloppyMath

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

public class SloppyMath
extends Object

Math functions that trade off accuracy for speed.

Constructor Summary

SloppyMath()

Method Summary

static double	asin(double a) Returns the arc sine of a value.
static double	cos(double a) Returns the trigonometric cosine of an angle.
static double	earthDiameter(double latitude) Return an approximate value of the diameter of the earth at the given latitude, in kilometers.
static double	haversin(double lat1, double lon1, double lat2, double lon2) Returns the distance in kilometers between two points specified in decimal degrees (latitude/longitude).

Methods inherited from class java.lang.Object

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

Constructor Detail

SloppyMath

public SloppyMath()

Method Detail

haversin

public static double haversin(double lat1,
                              double lon1,
                              double lat2,
                              double lon2)

Returns the distance in kilometers between two points specified in decimal degrees (latitude/longitude).

Parameters:

lat1 - Latitude of the first point.

lon1 - Longitude of the first point.

lat2 - Latitude of the second point.

lon2 - Longitude of the second point.

Returns:

distance in kilometers.

cos

public static double cos(double a)

Returns the trigonometric cosine of an angle.

Error is around 1E-15.

Special cases:

• If the argument is NaN or an infinity, then the result is NaN.

Parameters:

a - an angle, in radians.

Returns:

the cosine of the argument.

See Also:

Math.cos(double)

asin

public static double asin(double a)

Returns the arc sine of a value.

The returned angle is in the range -pi/2 through pi/2. Error is around 1E-7.

Special cases:

• If the argument is NaN or its absolute value is greater than 1, then the result is NaN.

Parameters:

a - the value whose arc sine is to be returned.

Returns:

arc sine of the argument

See Also:

Math.asin(double)

earthDiameter

public static double earthDiameter(double latitude)

Return an approximate value of the diameter of the earth at the given latitude, in kilometers.