com.sun.squawk.util
Class MathUtils

java.lang.Object
  com.sun.squawk.util.MathUtils

public class MathUtils
extends Object

The class MathUtils contains some of the Java SE Math routines that are not present in the CLDC 1.1 version of Math:

asin(double), acos(double), atan(double) & atan2(double, double).

The methods in this class are directly substitutable for the corresponding methods in Java SE java.lang.Math (circa JDK 1.2).

See Also:

java.lang.Math in Java SE, CLDC 1.1's java.lang.Math

Method Summary

static double	acos(double a) Returns the arc cosine of an angle, in the range of 0 through pi.
static double	asin(double a) Returns the arc sine of an angle, in the range of -pi/2 through pi/2.
static double	atan(double a) Returns the arc tangent of an angle, in the range of -pi/2 through pi/2.
static double	atan2(double y, double x) Converts rectangular coordinates (x, y) to polar (r, theta).
static double	exp(double a) Returns Euler's number e raised to the power of a double value.
static double	expm1(double a) Returns ex -1.
static double	IEEEremainder(double x, double p) Computes the remainder operation on two arguments as prescribed by the IEEE 754 standard.
static double	log(double a) Returns the natural logarithm (base e) of a double value.
static double	log1p(double a) Returns the natural logarithm of the sum of the argument and 1.
static double	pow(double x, double y) Returns the value of the first argument raised to the power of the second argument.
static double	rint(double a) Returns the double value that is closest in value to the argument and is equal to a mathematical integer.
static long	round(double a) Returns the closest long to the argument.
static int	round(float a) Returns the closest int to the argument.
static double	scalbn(double x, int n) Return d × 2scaleFactor rounded as if performed by a single correctly rounded floating-point multiply to a member of the double value set.

Methods inherited from class java.lang.Object

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

Method Detail

scalbn

public static double scalbn(double x,
                            int n)

Return d × 2^scaleFactor rounded as if performed by a single correctly rounded floating-point multiply to a member of the double value set. See the Java Language Specification for a discussion of floating-point value sets. If the exponent of the result is between Double#MIN_EXPONENT and Double#MAX_EXPONENT, the answer is calculated exactly. If the exponent of the result would be larger than Double.MAX_EXPONENT, an infinity is returned. Note that if the result is subnormal, precision may be lost; that is, when scalb(x, n) is subnormal, scalb(scalb(x, n), -n) may not equal x. When the result is non-NaN, the result has the same sign as d.

Special cases:

• If the first argument is NaN, NaN is returned.
• If the first argument is infinite, then an infinity of the same sign is returned.
• If the first argument is zero, then a zero of the same sign is returned.

Parameters:

x - number to be scaled by a power of two.

n - power of 2 used to scale d

Returns:

d × 2^scaleFactor

round

public static int round(float a)

Returns the closest int to the argument. The result is rounded to an integer by adding 1/2, taking the floor of the result, and casting the result to type int. In other words, the result is equal to the value of the expression:

(int)Math.floor(a + 0.5f)

Special cases:

• If the argument is NaN, the result is 0.
• If the argument is negative infinity or any value less than or equal to the value of Integer.MIN_VALUE, the result is equal to the value of Integer.MIN_VALUE.
• If the argument is positive infinity or any value greater than or equal to the value of Integer.MAX_VALUE, the result is equal to the value of Integer.MAX_VALUE.

Parameters:

a - a floating-point value to be rounded to an integer.

Returns:

the value of the argument rounded to the nearest int value.

See Also:

Integer.MAX_VALUE, Integer.MIN_VALUE

round

public static long round(double a)

Returns the closest long to the argument. The result is rounded to an integer by adding 1/2, taking the floor of the result, and casting the result to type long. In other words, the result is equal to the value of the expression:

(long)Math.floor(a + 0.5d)

Special cases:

• If the argument is NaN, the result is 0.
• If the argument is negative infinity or any value less than or equal to the value of Long.MIN_VALUE, the result is equal to the value of Long.MIN_VALUE.
• If the argument is positive infinity or any value greater than or equal to the value of Long.MAX_VALUE, the result is equal to the value of Long.MAX_VALUE.

Parameters:

a - a floating-point value to be rounded to a long.

Returns:

the value of the argument rounded to the nearest long value.

See Also:

Long.MAX_VALUE, Long.MIN_VALUE

exp

public static double exp(double a)

Returns Euler's number e raised to the power of a double value. Special cases:

• If the argument is NaN, the result is NaN.
• If the argument is positive infinity, then the result is positive infinity.
• If the argument is negative infinity, then the result is positive zero.

A result must be within 1 ulp of the correctly rounded result. Results must be semi-monotonic.

Parameters:

a - the exponent to raise e to.

Returns:

the value e^a, where e is the base of the natural logarithms.

log

public static double log(double a)

Returns the natural logarithm (base e) of a double value. Special cases:

• If the argument is NaN or less than zero, then the result is NaN.
• If the argument is positive infinity, then the result is positive infinity.
• If the argument is positive zero or negative zero, then the result is negative infinity.

A result must be within 1 ulp of the correctly rounded result. Results must be semi-monotonic.

Parameters:

a - a value

Returns:

the value ln a, the natural logarithm of a.

pow

public static double pow(double x,
                         double y)

Returns the value of the first argument raised to the power of the second argument. Special cases:

• If the second argument is positive or negative zero, then the result is 1.0.
• If the second argument is 1.0, then the result is the same as the first argument.
• If the second argument is NaN, then the result is NaN.
• If the first argument is NaN and the second argument is nonzero, then the result is NaN.
• If
  • the absolute value of the first argument is greater than 1 and the second argument is positive infinity, or
  • the absolute value of the first argument is less than 1 and the second argument is negative infinity,
  then the result is positive infinity.
• If
  • the absolute value of the first argument is greater than 1 and the second argument is negative infinity, or
  • the absolute value of the first argument is less than 1 and the second argument is positive infinity,
  then the result is positive zero.
• If the absolute value of the first argument equals 1 and the second argument is infinite, then the result is NaN.
• If
  • the first argument is positive zero and the second argument is greater than zero, or
  • the first argument is positive infinity and the second argument is less than zero,
  then the result is positive zero.
• If
  • the first argument is positive zero and the second argument is less than zero, or
  • the first argument is positive infinity and the second argument is greater than zero,
  then the result is positive infinity.
• If
  • the first argument is negative zero and the second argument is greater than zero but not a finite odd integer, or
  • the first argument is negative infinity and the second argument is less than zero but not a finite odd integer,
  then the result is positive zero.
• If
  • the first argument is negative zero and the second argument is a positive finite odd integer, or
  • the first argument is negative infinity and the second argument is a negative finite odd integer,
  then the result is negative zero.
• If
  • the first argument is negative zero and the second argument is less than zero but not a finite odd integer, or
  • the first argument is negative infinity and the second argument is greater than zero but not a finite odd integer,
  then the result is positive infinity.
• If
  • the first argument is negative zero and the second argument is a negative finite odd integer, or
  • the first argument is negative infinity and the second argument is a positive finite odd integer,
  then the result is negative infinity.
• If the first argument is finite and less than zero
  • if the second argument is a finite even integer, the result is equal to the result of raising the absolute value of the first argument to the power of the second argument
  • if the second argument is a finite odd integer, the result is equal to the negative of the result of raising the absolute value of the first argument to the power of the second argument
  • if the second argument is finite and not an integer, then the result is NaN.
• If both arguments are integers, then the result is exactly equal to the mathematical result of raising the first argument to the power of the second argument if that result can in fact be represented exactly as a double value.

(In the foregoing descriptions, a floating-point value is considered to be an integer if and only if it is finite and a fixed point of the method ceil or, equivalently, a fixed point of the method floor. A value is a fixed point of a one-argument method if and only if the result of applying the method to the value is equal to the value.)

A result must be within 1 ulp of the correctly rounded result. Results must be semi-monotonic.

Parameters:

x - the base.

y - the exponent.

Returns:

the value ab.

asin

public static double asin(double a)

Returns the arc sine of an angle, in the range of -pi/2 through pi/2. Special cases:

• If the argument is NaN or its absolute value is greater than 1, then the result is NaN.
• If the argument is zero, then the result is a zero with the same sign as the argument.

Parameters:

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

Returns:

the arc sine of the argument.

acos

public static double acos(double a)

Returns the arc cosine of an angle, in the range of 0 through pi. 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 cosine is to be returned.

Returns:

the arc cosine of the argument.

atan

public static double atan(double a)

Returns the arc tangent of an angle, in the range of -pi/2 through pi/2. 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.

Parameters:

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

Returns:

the arc tangent of the argument.

atan2

public static double atan2(double y,
                           double x)

Converts rectangular coordinates (x, y) to polar (r, theta). This method computes the phase theta by computing an arc tangent of y/x in the range of -pi to pi. Special cases:

• If either argument is NaN, then the result is NaN.
• If the first argument is positive zero and the second argument is positive, or the first argument is positive and finite and the second argument is positive infinity, then the result is positive zero.
• If the first argument is negative zero and the second argument is positive, or the first argument is negative and finite and the second argument is positive infinity, then the result is negative zero.
• If the first argument is positive zero and the second argument is negative, or the first argument is positive and finite and the second argument is negative infinity, then the result is the double value closest to pi.
• If the first argument is negative zero and the second argument is negative, or the first argument is negative and finite and the second argument is negative infinity, then the result is the double value closest to -pi.
• If the first argument is positive and the second argument is positive zero or negative zero, or the first argument is positive infinity and the second argument is finite, then the result is the double value closest to pi/2.
• If the first argument is negative and the second argument is positive zero or negative zero, or the first argument is negative infinity and the second argument is finite, then the result is the double value closest to -pi/2.
• If both arguments are positive infinity, then the result is the double value closest to pi/4.
• If the first argument is positive infinity and the second argument is negative infinity, then the result is the double value closest to 3*pi/4.
• If the first argument is negative infinity and the second argument is positive infinity, then the result is the double value closest to -pi/4.
• If both arguments are negative infinity, then the result is the double value closest to -3*pi/4.

Parameters:

y - the ordinate coordinate

x - the abscissa coordinate

Returns:

the theta component of the point (r, theta) in polar coordinates that corresponds to the point (x, y) in Cartesian coordinates.

rint

public static double rint(double a)

Returns the double value that is closest in value to the argument and is equal to a mathematical integer. If two double values that are mathematical integers are equally close, the result is the integer value that is even. Special cases:

• If the argument value is already equal to a mathematical integer, then the result is the same as the argument.
• If the argument is NaN or an infinity or positive zero or negative zero, then the result is the same as the argument.

Parameters:

a - a double value.

Returns:

the closest floating-point value to a that is equal to a mathematical integer.

log1p

public static double log1p(double a)

Returns the natural logarithm of the sum of the argument and 1. Note that for small values x, the result of log1p(x) is much closer to the true result of ln(1 + x) than the floating-point evaulation of log(1.0+x).

Special cases:

• If the argument is NaN or less than -1, then the result is NaN.
• If the argument is positive infinity, then the result is positive infinity.
• If the argument is negative one, then the result is negative infinity.
• If the argument is zero, then the result is a zero with the same sign as the argument.

A result must be within 1 ulp of the correctly rounded result. Results must be semi-monotonic.

Parameters:

a - a value

Returns:

the value ln(x + 1), the natural log of x + 1

expm1

public static double expm1(double a)

Returns e^x -1. Note that for values of x near 0, the exact sum of expm1(x) + 1 is much closer to the true result of e^x than exp(x).

Special cases:

• If the argument is NaN, the result is NaN.
• If the argument is positive infinity, then the result is positive infinity.
• If the argument is negative infinity, then the result is -1.0.
• If the argument is zero, then the result is a zero with the same sign as the argument.

A result must be within 1 ulp of the correctly rounded result. Results must be semi-monotonic. The result of expm1 for any finite input must be greater than or equal to -1.0. Note that once the exact result of e^x - 1 is within 1/2 ulp of the limit value -1, -1.0 should be returned.

Parameters:

a - the exponent to raise e to in the computation of e^x -1.

Returns:

the value e^x - 1.

IEEEremainder

public static double IEEEremainder(double x,
                                   double p)

Computes the remainder operation on two arguments as prescribed by the IEEE 754 standard. The remainder value is mathematically equal to f1 - f2 × n, where n is the mathematical integer closest to the exact mathematical value of the quotient f1/f2, and if two mathematical integers are equally close to f1/f2, then n is the integer that is even. If the remainder is zero, its sign is the same as the sign of the first argument. Special cases:

• If either argument is NaN, or the first argument is infinite, or the second argument is positive zero or negative zero, then the result is NaN.
• If the first argument is finite and the second argument is infinite, then the result is the same as the first argument.

Parameters:

x - the dividend.

p - the divisor.

Returns:

the remainder when f1 is divided by f2.