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.

Field Summary

Fields

Modifier and Type	Field and Description
static double	PIO2
static double	TO_DEGREES
static double	TO_RADIANS

Constructor Summary

Constructors

Constructor and Description
SloppyMath()

Method Summary

Methods

Modifier and Type	Method and Description
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 Haversine distance in kilometers between two points specified in decimal degrees (latitude/longitude).
static double	sin(double a) Returns the trigonometric sine of an angle converted as a cos operation.
static double	tan(double a) Returns the trigonometric tangent of an angle converted in terms of a sin/cos operation.

Methods inherited from class java.lang.Object

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

Field Detail

TO_RADIANS

public static final double TO_RADIANS

See Also:

Constant Field Values

TO_DEGREES

public static final double TO_DEGREES

See Also:

Constant Field Values

PIO2

public static final double PIO2

See Also:

Constant Field Values

Constructor Detail

SloppyMath

public SloppyMath()

Method Detail

haversin

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

Returns the Haversine distance in kilometers between two points specified in decimal degrees (latitude/longitude). This works correctly even if the dateline is between the two points.

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)

sin

public static double sin(double a)

Returns the trigonometric sine of an angle converted as a cos operation.

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 sine of the argument.

See Also:

Math.cos(double)

tan

public static double tan(double a)

Returns the trigonometric tangent of an angle converted in terms of a sin/cos operation.

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 tangent of the argument.

See Also:

aand 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.