| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.commons.numbers.complex; |
| |
| import java.io.Serializable; |
| import java.util.ArrayList; |
| import java.util.List; |
| |
| import org.apache.commons.numbers.core.Precision; |
| |
| /** |
| * Cartesian representation of a complex number, i.e. a number which has both a |
| * real and imaginary part. |
| * |
| * <p>This class is immutable. All arithmetic will create a new instance for the |
| * result.</p> |
| * |
| * <p>Arithmetic in this class conforms to the C99 standard for complex numbers |
| * defined in ISO/IEC 9899, Annex G. All methods have been named using the equivalent |
| * method in ISO C99. The behaviour for special cases is listed as defined in C99.</p> |
| * |
| * <p>For functions \( f \) which obey the conjugate equality \( conj(f(z)) = f(conj(z)) \), |
| * the specifications for the upper half-plane imply the specifications for the lower |
| * half-plane.</p> |
| * |
| * <p>For functions that are either odd, \( f(z) = -f(-z) \), or even, \( f(z) = f(-z) \) |
| * the specifications for the first quadrant imply the specifications for the other three |
| * quadrants.</p> |
| * |
| * @see <a href="http://www.open-std.org/JTC1/SC22/WG14/www/standards"> |
| * ISO/IEC 9899 - Programming languages - C</a> |
| */ |
| public final class Complex implements Serializable { |
| /** |
| * A complex number representing \( i \), the square root of \( -1 \). |
| * |
| * <p>\( (0 + i 1) \). |
| */ |
| public static final Complex I = new Complex(0, 1); |
| /** |
| * A complex number representing one. |
| * |
| * <p>\( (1 + i 0) \). |
| */ |
| public static final Complex ONE = new Complex(1, 0); |
| /** |
| * A complex number representing zero. |
| * |
| * <p>\( (0 + i 0) \). |
| */ |
| public static final Complex ZERO = new Complex(0, 0); |
| |
| /** A complex number representing {@code NaN + i NaN}. */ |
| private static final Complex NAN = new Complex(Double.NaN, Double.NaN); |
| /** π/2. */ |
| private static final double PI_OVER_2 = 0.5 * Math.PI; |
| /** π/4. */ |
| private static final double PI_OVER_4 = 0.25 * Math.PI; |
| /** Mask an integer number to even by discarding the lowest bit. */ |
| private static final int MASK_INT_TO_EVEN = ~0x1; |
| /** Natural logarithm of 2 (ln(2)). */ |
| private static final double LN_2 = Math.log(2); |
| /** Base 10 logarithm of 10 divided by 2 (log10(e)/2). */ |
| private static final double LOG_10E_O_2 = Math.log10(Math.E) / 2; |
| /** Base 10 logarithm of 2 (log10(2)). */ |
| private static final double LOG10_2 = Math.log10(2); |
| /** {@code 1/2}. */ |
| private static final double HALF = 0.5; |
| /** {@code sqrt(2)}. */ |
| private static final double ROOT2 = Math.sqrt(2); |
| /** The number of bits of precision of the mantissa of a {@code double} + 1: {@code 54}. */ |
| private static final double PRECISION_1 = 54; |
| /** The bit representation of {@code -0.0}. */ |
| private static final long NEGATIVE_ZERO_LONG_BITS = Double.doubleToLongBits(-0.0); |
| |
| /** |
| * Crossover point to switch computation for asin/acos factor A. |
| * This has been updated from the 1.5 value used by Hull et al to 10 |
| * as used in boost::math::complex. |
| * @see <a href="https://svn.boost.org/trac/boost/ticket/7290">Boost ticket 7290</a> |
| */ |
| private static final double A_CROSSOVER = 10; |
| /** Crossover point to switch computation for asin/acos factor B. */ |
| private static final double B_CROSSOVER = 0.6471; |
| /** |
| * The safe maximum double value {@code x} to avoid loss of precision in asin/acos. |
| * Equal to sqrt(M) / 8 in Hull, et al (1997) with M the largest normalised floating-point value. |
| */ |
| private static final double SAFE_MAX = Math.sqrt(Double.MAX_VALUE) / 8; |
| /** |
| * The safe minimum double value {@code x} to avoid loss of precision/underflow in asin/acos. |
| * Equal to sqrt(u) * 4 in Hull, et al (1997) with u the smallest normalised floating-point value. |
| */ |
| private static final double SAFE_MIN = Math.sqrt(Double.MIN_NORMAL) * 4; |
| /** |
| * The safe maximum double value {@code x} to avoid loss of precision in atanh. |
| * Equal to sqrt(M) / 2 with M the largest normalised floating-point value. |
| */ |
| private static final double SAFE_UPPER = Math.sqrt(Double.MAX_VALUE) / 2; |
| /** |
| * The safe minimum double value {@code x} to avoid loss of precision/underflow in atanh. |
| * Equal to sqrt(u) * 2 with u the smallest normalised floating-point value. |
| */ |
| private static final double SAFE_LOWER = Math.sqrt(Double.MIN_NORMAL) * 2; |
| |
| /** Serializable version identifier. */ |
| private static final long serialVersionUID = 20180201L; |
| |
| /** |
| * The size of the buffer for {@link #toString()}. |
| * |
| * <p>The longest double will require a sign, a maximum of 17 digits, the decimal place |
| * and the exponent, e.g. for max value this is 24 chars: -1.7976931348623157e+308. |
| * Set the buffer size to twice this and round up to a power of 2 thus |
| * allowing for formatting characters. The size is 64. |
| */ |
| private static final int TO_STRING_SIZE = 64; |
| /** The minimum number of characters in the format. This is 5, e.g. {@code "(0,0)"}. */ |
| private static final int FORMAT_MIN_LEN = 5; |
| /** {@link #toString() String representation}. */ |
| private static final char FORMAT_START = '('; |
| /** {@link #toString() String representation}. */ |
| private static final char FORMAT_END = ')'; |
| /** {@link #toString() String representation}. */ |
| private static final char FORMAT_SEP = ','; |
| /** The minimum number of characters before the separator. This is 2, e.g. {@code "(0"}. */ |
| private static final int BEFORE_SEP = 2; |
| |
| /** The imaginary part. */ |
| private final double imaginary; |
| /** The real part. */ |
| private final double real; |
| |
| /** |
| * Define a constructor for a Complex. |
| * This is used in functions that implement trigonomic identities. |
| */ |
| @FunctionalInterface |
| private interface ComplexConstructor { |
| /** |
| * Create a complex number given the real and imaginary parts. |
| * |
| * @param real Real part. |
| * @param imaginary Imaginary part. |
| * @return {@code Complex} object. |
| */ |
| Complex create(double real, double imaginary); |
| } |
| |
| /** |
| * Define a unary operation on a double. |
| * This is used in the log() and log10() functions. |
| */ |
| @FunctionalInterface |
| private interface UnaryOperation { |
| /** |
| * Apply an operation to a value. |
| * |
| * @param value The value. |
| * @return The result. |
| */ |
| double apply(double value); |
| } |
| |
| /** |
| * Private default constructor. |
| * |
| * @param real Real part. |
| * @param imaginary Imaginary part. |
| */ |
| private Complex(double real, double imaginary) { |
| this.real = real; |
| this.imaginary = imaginary; |
| } |
| |
| /** |
| * Create a complex number given the real and imaginary parts. |
| * |
| * @param real Real part. |
| * @param imaginary Imaginary part. |
| * @return {@code Complex} number. |
| */ |
| public static Complex ofCartesian(double real, double imaginary) { |
| return new Complex(real, imaginary); |
| } |
| |
| /** |
| * Creates a complex number from its polar representation using modulus {@code rho} (\( \rho \)) |
| * and phase angle {@code theta} (\( \theta \)). |
| * |
| * \[ x = \rho \cos(\theta) \\ |
| * y = \rho \sin(\theta) \] |
| * |
| * <p>Requires that {@code rho} is non-negative and non-NaN and {@code theta} is finite; |
| * otherwise returns a complex with NaN real and imaginary parts. A value of {@code -0.0} is |
| * considered negative and an invalid modulus. |
| * |
| * <p>A non-NaN complex number constructed using this method will satisfy the following |
| * to within floating-point error when {@code theta} is in the range |
| * \( -\pi\ \lt \theta \leq \pi \):</p> |
| * <pre> |
| * Complex.ofPolar(rho, theta).abs() == rho |
| * Complex.ofPolar(rho, theta).arg() == theta </pre> |
| * |
| * <p>If {@code rho} is infinite then the resulting parts may be infinite or NaN |
| * following the rules for double arithmetic, for example:</p> |
| * |
| * <ul> |
| * <li>{@code ofPolar(}\( -0.0 \){@code , }\( 0 \){@code ) = }\( \text{NaN} + i \text{NaN} \) |
| * <li>{@code ofPolar(}\( 0.0 \){@code , }\( 0 \){@code ) = }\( 0 + i 0 \) |
| * <li>{@code ofPolar(}\( 1 \){@code , }\( 0 \){@code ) = }\( 1 + i 0 \) |
| * <li>{@code ofPolar(}\( 1 \){@code , }\( \pi \){@code ) = }\( -1 + i \sin(\pi) \) |
| * <li>{@code ofPolar(}\( \infty \){@code , }\( \pi \){@code ) = }\( -\infty + i \infty \) |
| * <li>{@code ofPolar(}\( \infty \){@code , }\( 0 \){@code ) = }\( -\infty + i \text{NaN} \) |
| * <li>{@code ofPolar(}\( \infty \){@code , }\( -\frac{\pi}{4} \){@code ) = }\( \infty - i \infty \) |
| * <li>{@code ofPolar(}\( \infty \){@code , }\( 5\frac{\pi}{4} \){@code ) = }\( -\infty - i \infty \) |
| * </ul> |
| * |
| * <p>This method is the functional equivalent of the C++ method {@code std::polar}. |
| * |
| * @param rho The modulus of the complex number. |
| * @param theta The argument of the complex number. |
| * @return {@code Complex} number. |
| * @see <a href="http://mathworld.wolfram.com/PolarCoordinates.html">Polar Coordinates</a> |
| */ |
| public static Complex ofPolar(double rho, double theta) { |
| // Require finite theta and non-negative, non-nan rho |
| if (!Double.isFinite(theta) || negative(rho) || Double.isNaN(rho)) { |
| return NAN; |
| } |
| final double x = rho * Math.cos(theta); |
| final double y = rho * Math.sin(theta); |
| return new Complex(x, y); |
| } |
| |
| /** |
| * Create a complex cis number. This is also known as the complex exponential: |
| * |
| * \[ \text{cis}(x) = e^{ix} = \cos(x) + i \sin(x) \] |
| * |
| * @param x {@code double} to build the cis number. |
| * @return {@code Complex} cis number. |
| * @see <a href="http://mathworld.wolfram.com/Cis.html">Cis</a> |
| */ |
| public static Complex ofCis(double x) { |
| return new Complex(Math.cos(x), Math.sin(x)); |
| } |
| |
| /** |
| * Returns a {@code Complex} instance representing the specified string {@code s}. |
| * |
| * <p>If {@code s} is {@code null}, then a {@code NullPointerException} is thrown. |
| * |
| * <p>The string must be in a format compatible with that produced by |
| * {@link #toString() Complex.toString()}. |
| * The format expects a start and end parentheses surrounding two numeric parts split |
| * by a separator. Leading and trailing spaces are allowed around each numeric part. |
| * Each numeric part is parsed using {@link Double#parseDouble(String)}. The parts |
| * are interpreted as the real and imaginary parts of the complex number. |
| * |
| * <p>Examples of valid strings and the equivalent {@code Complex} are shown below: |
| * |
| * <pre> |
| * "(0,0)" = Complex.ofCartesian(0, 0) |
| * "(0.0,0.0)" = Complex.ofCartesian(0, 0) |
| * "(-0.0, 0.0)" = Complex.ofCartesian(-0.0, 0) |
| * "(-1.23, 4.56)" = Complex.ofCartesian(-123, 4.56) |
| * "(1e300,-1.1e-2)" = Complex.ofCartesian(1e300, -1.1e-2) |
| * </pre> |
| * |
| * @param s String representation. |
| * @return {@code Complex} number. |
| * @throws NullPointerException if the string is null. |
| * @throws NumberFormatException if the string does not contain a parsable complex number. |
| * @see Double#parseDouble(String) |
| * @see #toString() |
| */ |
| public static Complex parse(String s) { |
| final int len = s.length(); |
| if (len < FORMAT_MIN_LEN) { |
| throw parsingException("Expected format", |
| FORMAT_START + "real" + FORMAT_SEP + "imaginary" + FORMAT_END, null); |
| } |
| |
| // Confirm start: '(' |
| if (s.charAt(0) != FORMAT_START) { |
| throw parsingException("Expected start", FORMAT_START, null); |
| } |
| |
| // Confirm end: ')' |
| if (s.charAt(len - 1) != FORMAT_END) { |
| throw parsingException("Expected end", FORMAT_END, null); |
| } |
| |
| // Confirm separator ',' is between at least 2 characters from |
| // either end: "(x,x)" |
| // Count back from the end ignoring the last 2 characters. |
| final int sep = s.lastIndexOf(FORMAT_SEP, len - 3); |
| if (sep < BEFORE_SEP) { |
| throw parsingException("Expected separator between two numbers", FORMAT_SEP, null); |
| } |
| |
| // Should be no more separators |
| if (s.indexOf(FORMAT_SEP, sep + 1) != -1) { |
| throw parsingException("Incorrect number of parts, expected only 2 using separator", |
| FORMAT_SEP, null); |
| } |
| |
| // Try to parse the parts |
| |
| final String rePart = s.substring(1, sep); |
| final double re; |
| try { |
| re = Double.parseDouble(rePart); |
| } catch (final NumberFormatException ex) { |
| throw parsingException("Could not parse real part", rePart, ex); |
| } |
| |
| final String imPart = s.substring(sep + 1, len - 1); |
| final double im; |
| try { |
| im = Double.parseDouble(imPart); |
| } catch (final NumberFormatException ex) { |
| throw parsingException("Could not parse imaginary part", imPart, ex); |
| } |
| |
| return ofCartesian(re, im); |
| } |
| |
| /** |
| * Returns {@code true} if either the real <em>or</em> imaginary component of the complex number is NaN |
| * <em>and</em> the complex number is not infinite. |
| * |
| * <p>Note that in contrast to {@link Double#isNaN()}: |
| * <ul> |
| * <li>There is more than one complex number that can return {@code true}. |
| * <li>Different representations of NaN can be distinguished by the |
| * {@link #equals(Object) Complex.equals(Object)} method. |
| * </ul> |
| * |
| * @return {@code true} if this instance contains NaN and no infinite parts. |
| * @see Double#isNaN(double) |
| * @see #isInfinite() |
| * @see #equals(Object) Complex.equals(Object) |
| */ |
| public boolean isNaN() { |
| if (Double.isNaN(real) || Double.isNaN(imaginary)) { |
| return !isInfinite(); |
| } |
| return false; |
| } |
| |
| /** |
| * Returns {@code true} if either real or imaginary component of the complex number is infinite. |
| * |
| * <p>Note: A complex or imaginary value with at least one infinite part is regarded |
| * as an infinity (even if its other part is a NaN).</p> |
| * |
| * @return {@code true} if this instance contains an infinite value. |
| * @see Double#isInfinite(double) |
| */ |
| public boolean isInfinite() { |
| return Double.isInfinite(real) || Double.isInfinite(imaginary); |
| } |
| |
| /** |
| * Returns {@code true} if both real and imaginary component of the complex number are finite. |
| * |
| * @return {@code true} if this instance contains finite values. |
| * @see Double#isFinite(double) |
| */ |
| public boolean isFinite() { |
| return Double.isFinite(real) && Double.isFinite(imaginary); |
| } |
| |
| /** |
| * Returns projection of this complex number onto the Riemann sphere. |
| * |
| * <p>\( z \) projects to \( z \), except that all complex infinities (even those |
| * with one infinite part and one NaN part) project to positive infinity on the real axis. |
| * |
| * If \( z \) has an infinite part, then {@code z.proj()} shall be equivalent to:</p> |
| * <pre> |
| * return Complex.ofCartesian(Double.POSITIVE_INFINITY, Math.copySign(0.0, z.imag()); |
| * </pre> |
| * |
| * @return \( z \) projected onto the Riemann sphere. |
| * @see #isInfinite() |
| * @see <a href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/cproj.html"> |
| * IEEE and ISO C standards: cproj</a> |
| */ |
| public Complex proj() { |
| if (isInfinite()) { |
| return new Complex(Double.POSITIVE_INFINITY, Math.copySign(0.0, imaginary)); |
| } |
| return this; |
| } |
| |
| /** |
| * Returns the absolute value of this complex number. This is also called complex norm, modulus, |
| * or magnitude. |
| * |
| * <p>\[ \text{abs}(x + i y) = \sqrt{(x^2 + y^2)} \] |
| * |
| * <p>If either component is infinite then the result is positive infinity. If either |
| * component is NaN and this is not {@link #isInfinite() infinite} then the result is NaN. |
| * |
| * <p>This code follows the |
| * <a href="http://www.iso-9899.info/wiki/The_Standard">ISO C Standard</a>, Annex G, |
| * in calculating the returned value using the {@code hypot(x, y)} method for complex |
| * \( x + i y \). |
| * |
| * @return The absolute value. |
| * @see #isInfinite() |
| * @see #isNaN() |
| * @see Math#hypot(double, double) |
| * @see <a href="http://mathworld.wolfram.com/ComplexModulus.html">Complex modulus</a> |
| */ |
| public double abs() { |
| // Delegate |
| return Math.hypot(real, imaginary); |
| } |
| |
| /** |
| * Returns the squared norm value of this complex number. This is also called the absolute |
| * square. |
| * |
| * <p>\[ \text{norm}(x + i y) = x^2 + y^2 \] |
| * |
| * <p>If either component is infinite then the result is positive infinity. If either |
| * component is NaN and this is not {@link #isInfinite() infinite} then the result is NaN. |
| * |
| * <p>This method will return the square of {@link #abs()}. It can be used as a faster |
| * alternative for ranking by magnitude although overflow to infinity will create equal |
| * ranking for values that may be still distinguished by {@code abs()}. |
| * |
| * @return The square norm value. |
| * @see #isInfinite() |
| * @see #isNaN() |
| * @see #abs() |
| * @see <a href="http://mathworld.wolfram.com/AbsoluteSquare.html">Absolute square</a> |
| */ |
| public double norm() { |
| if (isInfinite()) { |
| return Double.POSITIVE_INFINITY; |
| } |
| return real * real + imaginary * imaginary; |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code (this + addend)}. |
| * Implements the formula: |
| * |
| * <p>\[ (a + i b) + (c + i d) = (a + c) + i (b + d) \] |
| * |
| * @param addend Value to be added to this complex number. |
| * @return {@code this + addend}. |
| * @see <a href="http://mathworld.wolfram.com/ComplexAddition.html">Complex Addition</a> |
| */ |
| public Complex add(Complex addend) { |
| return new Complex(real + addend.real, |
| imaginary + addend.imaginary); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code (this + addend)}, |
| * with {@code addend} interpreted as a real number. |
| * Implements the formula: |
| * |
| * <p>\[ (a + i b) + c = (a + c) + i b \] |
| * |
| * <p>This method is included for compatibility with ISO C99 which defines arithmetic between |
| * real-only and complex numbers.</p> |
| * |
| * <p>Note: This method preserves the sign of the imaginary component \( b \) if it is {@code -0.0}. |
| * The sign would be lost if adding \( (c + i 0) \) using |
| * {@link #add(Complex) add(Complex.ofCartesian(addend, 0))} since |
| * {@code -0.0 + 0.0 = 0.0}. |
| * |
| * @param addend Value to be added to this complex number. |
| * @return {@code this + addend}. |
| * @see #add(Complex) |
| * @see #ofCartesian(double, double) |
| */ |
| public Complex add(double addend) { |
| return new Complex(real + addend, imaginary); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code (this + addend)}, |
| * with {@code addend} interpreted as an imaginary number. |
| * Implements the formula: |
| * |
| * <p>\[ (a + i b) + i d = a + i (b + d) \] |
| * |
| * <p>This method is included for compatibility with ISO C99 which defines arithmetic between |
| * imaginary-only and complex numbers.</p> |
| * |
| * <p>Note: This method preserves the sign of the real component \( a \) if it is {@code -0.0}. |
| * The sign would be lost if adding \( (0 + i d) \) using |
| * {@link #add(Complex) add(Complex.ofCartesian(0, addend))} since |
| * {@code -0.0 + 0.0 = 0.0}. |
| * |
| * @param addend Value to be added to this complex number. |
| * @return {@code this + addend}. |
| * @see #add(Complex) |
| * @see #ofCartesian(double, double) |
| */ |
| public Complex addImaginary(double addend) { |
| return new Complex(real, imaginary + addend); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/ComplexConjugate.html">conjugate</a> |
| * \( \overline{z} \) of this complex number \( z \). |
| * |
| * <p>\[ z = x + i y \\ |
| * \overline{z} = x - i y \] |
| * |
| * @return The conjugate (\( \overline{z} \)) of this complex number. |
| */ |
| public Complex conj() { |
| return new Complex(real, -imaginary); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code (this / divisor)}. |
| * Implements the formula: |
| * |
| * <p>\[ \frac{a + i b}{c + i d} = \frac{(ac + bd) + i (bc - ad)}{c^2+d^2} \] |
| * |
| * <p>Re-calculates NaN result values to recover infinities as specified in C99 standard G.5.1. |
| * |
| * @param divisor Value by which this complex number is to be divided. |
| * @return {@code this / divisor}. |
| * @see <a href="http://mathworld.wolfram.com/ComplexDivision.html">Complex Division</a> |
| */ |
| public Complex divide(Complex divisor) { |
| return divide(real, imaginary, divisor.real, divisor.imaginary); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is: |
| * <pre> |
| * <code> |
| * a + i b (ac + bd) + i (bc - ad) |
| * ------- = ----------------------- |
| * c + i d c<sup>2</sup> + d<sup>2</sup> |
| * </code> |
| * </pre> |
| * |
| * <p>Recalculates to recover infinities as specified in C99 |
| * standard G.5.1. Method is fully in accordance with |
| * C++11 standards for complex numbers.</p> |
| * |
| * <p>Note: In the event of divide by zero this method produces the same result |
| * as dividing by a real-only zero using {@link #divide(double)}. |
| * |
| * @param re1 Real component of first number. |
| * @param im1 Imaginary component of first number. |
| * @param re2 Real component of second number. |
| * @param im2 Imaginary component of second number. |
| * @return (a + i b) / (c + i d). |
| * @see <a href="http://mathworld.wolfram.com/ComplexDivision.html">Complex Division</a> |
| * @see #divide(double) |
| */ |
| private static Complex divide(double re1, double im1, double re2, double im2) { |
| double a = re1; |
| double b = im1; |
| double c = re2; |
| double d = im2; |
| int ilogbw = 0; |
| // Get the exponent to scale the divisor. |
| final int exponent = getMaxExponent(c, d); |
| if (exponent <= Double.MAX_EXPONENT) { |
| ilogbw = exponent; |
| c = Math.scalb(c, -ilogbw); |
| d = Math.scalb(d, -ilogbw); |
| } |
| final double denom = c * c + d * d; |
| double x = Math.scalb((a * c + b * d) / denom, -ilogbw); |
| double y = Math.scalb((b * c - a * d) / denom, -ilogbw); |
| // Recover infinities and zeros that computed as NaN+iNaN |
| // the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... |
| // -------------- |
| // Modification from the listing in ISO C99 G.5.1 (8): |
| // Prevent overflow in (a * c + b * d) and (b * c - a * d). |
| // It is only the sign that is important. not the magnitude. |
| // -------------- |
| if (Double.isNaN(x) && Double.isNaN(y)) { |
| if ((denom == 0.0) && |
| (!Double.isNaN(a) || !Double.isNaN(b))) { |
| // nonzero/zero |
| // This case produces the same result as divide by a real-only zero |
| // using divide(+/-0.0). |
| x = Math.copySign(Double.POSITIVE_INFINITY, c) * a; |
| y = Math.copySign(Double.POSITIVE_INFINITY, c) * b; |
| } else if ((Double.isInfinite(a) || Double.isInfinite(b)) && |
| Double.isFinite(c) && Double.isFinite(d)) { |
| // infinite/finite |
| a = boxInfinity(a); |
| b = boxInfinity(b); |
| x = Double.POSITIVE_INFINITY * computeACplusBD(a, b, c, d); |
| y = Double.POSITIVE_INFINITY * computeBCminusAD(a, b, c, d); |
| } else if ((Double.isInfinite(c) || Double.isInfinite(d)) && |
| Double.isFinite(a) && Double.isFinite(b)) { |
| // finite/infinite |
| c = boxInfinity(c); |
| d = boxInfinity(d); |
| x = 0.0 * computeACplusBD(a, b, c, d); |
| y = 0.0 * computeBCminusAD(a, b, c, d); |
| } |
| } |
| return new Complex(x, y); |
| } |
| |
| /** |
| * Compute {@code a*c + b*d} without overflow. |
| * It is assumed: either {@code a} an\( b \)b} or {@code c} and {@code d} are |
| * either zero or one (i.e. a boxed infinity); and the sign of the result is important, |
| * not the value. |
| * |
| * @param a the a |
| * @param b the b |
| * @param c the c |
| * @param d the d |
| * @return The result |
| */ |
| private static double computeACplusBD(double a, double b, double c, double d) { |
| final double ac = a * c; |
| final double bd = b * d; |
| final double result = ac + bd; |
| return Double.isFinite(result) ? |
| result : |
| // Overflow. Just divide by 2 as it is the sign of the result that matters. |
| ac * 0.5 + bd * 0.5; |
| } |
| |
| /** |
| * Compute {@code b*c - a*d} without overflow. |
| * It is assumed: either {@code a} and {@code b} or {@code c} and {@code d} are |
| * either zero or one (i.e. a boxed infinity); and the sign of the result is important, |
| * not the value. |
| * |
| * @param a the a |
| * @param b the b |
| * @param c the c |
| * @param d the d |
| * @return The result |
| */ |
| private static double computeBCminusAD(double a, double b, double c, double d) { |
| final double bc = b * c; |
| final double ad = a * d; |
| final double result = bc - ad; |
| return Double.isFinite(result) ? |
| result : |
| // Overflow. Just divide by 2 as it is the sign of the result that matters. |
| bc * 0.5 - ad * 0.5; |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code (this / divisor)}, |
| * with {@code divisor} interpreted as a real number. |
| * Implements the formula: |
| * |
| * <p>\[ \frac{a + i b}{c} = \frac{a}{c} + i \frac{b}{c} \] |
| * |
| * <p>This method is included for compatibility with ISO C99 which defines arithmetic between |
| * real-only and complex numbers.</p> |
| * |
| * <p>Note: This method should be preferred over using |
| * {@link #divide(Complex) divide(Complex.ofCartesian(divisor, 0))}. Division |
| * can generate signed zeros if {@code this} complex has zeros for the real |
| * and/or imaginary component, or the divisor is infinity. The summation of signed zeros |
| * in {@link #divide(Complex)} may create zeros in the result that differ in sign |
| * from the equivalent call to divide by a real-only number. |
| * |
| * @param divisor Value by which this complex number is to be divided. |
| * @return {@code this / divisor}. |
| * @see #divide(Complex) |
| */ |
| public Complex divide(double divisor) { |
| return new Complex(real / divisor, imaginary / divisor); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code (this / divisor)}, |
| * with {@code divisor} interpreted as an imaginary number. |
| * Implements the formula: |
| * |
| * <p>\[ \frac{a + i b}{id} = \frac{b}{d} - i \frac{a}{d} \] |
| * |
| * <p>This method is included for compatibility with ISO C99 which defines arithmetic between |
| * imaginary-only and complex numbers.</p> |
| * |
| * <p>Note: This method should be preferred over using |
| * {@link #divide(Complex) divide(Complex.ofCartesian(0, divisor))}. Division |
| * can generate signed zeros if {@code this} complex has zeros for the real |
| * and/or imaginary component, or the divisor is infinity. The summation of signed zeros |
| * in {@link #divide(Complex)} may create zeros in the result that differ in sign |
| * from the equivalent call to divide by an imaginary-only number. |
| * |
| * <p>Warning: This method will generate a different result from |
| * {@link #divide(Complex) divide(Complex.ofCartesian(0, divisor))} if the divisor is zero. |
| * In this case the divide method using a zero-valued Complex will produce the same result |
| * as dividing by a real-only zero. The output from dividing by imaginary zero will create |
| * infinite and NaN values in the same component parts as the output from |
| * {@code this.divide(Complex.ZERO).multiplyImaginary(1)}, however the sign |
| * of some infinity values may be negated. |
| * |
| * @param divisor Value by which this complex number is to be divided. |
| * @return {@code this / divisor}. |
| * @see #divide(Complex) |
| * @see #divide(double) |
| */ |
| public Complex divideImaginary(double divisor) { |
| return new Complex(imaginary / divisor, -real / divisor); |
| } |
| |
| /** |
| * Test for equality with another object. If the other object is a {@code Complex} then a |
| * comparison is made of the real and imaginary parts; otherwise {@code false} is returned. |
| * |
| * <p>If both the real and imaginary parts of two complex numbers |
| * are exactly the same the two {@code Complex} objects are considered to be equal. |
| * For this purpose, two {@code double} values are considered to be |
| * the same if and only if the method {@link Double #doubleToLongBits(double)} |
| * returns the identical {@code long} value when applied to each. |
| * |
| * <p>Note that in most cases, for two instances of class |
| * {@code Complex}, {@code c1} and {@code c2}, the |
| * value of {@code c1.equals(c2)} is {@code true} if and only if |
| * |
| * <pre> |
| * {@code c1.getReal() == c2.getReal() && c1.getImaginary() == c2.getImaginary()}</pre> |
| * |
| * <p>also has the value {@code true}. However, there are exceptions: |
| * |
| * <ul> |
| * <li> |
| * Instances that contain {@code NaN} values in the same part |
| * are considered to be equal for that part, even though {@code Double.NaN==Double.NaN} |
| * has the value {@code false}. |
| * </li> |
| * <li> |
| * Instances that share a {@code NaN} value in one part |
| * but have different values in the other part are <em>not</em> considered equal. |
| * </li> |
| * <li> |
| * Instances that contain different representations of zero in the same part |
| * are <em>not</em> considered to be equal for that part, even though {@code -0.0==0.0} |
| * has the value {@code true}. |
| * </li> |
| * </ul> |
| * |
| * <p>The behavior is the same as if the components of the two complex numbers were passed |
| * to {@link java.util.Arrays#equals(double[], double[]) Arrays.equals(double[], double[])}: |
| * |
| * <pre> |
| * Arrays.equals(new double[]{c1.getReal(), c1.getImaginary()}, |
| * new double[]{c2.getReal(), c2.getImaginary()}); </pre> |
| * |
| * @param other Object to test for equality with this instance. |
| * @return {@code true} if the objects are equal, {@code false} if object |
| * is {@code null}, not an instance of {@code Complex}, or not equal to |
| * this instance. |
| * @see java.lang.Double#doubleToLongBits(double) |
| * @see java.util.Arrays#equals(double[], double[]) |
| */ |
| @Override |
| public boolean equals(Object other) { |
| if (this == other) { |
| return true; |
| } |
| if (other instanceof Complex) { |
| final Complex c = (Complex) other; |
| return equals(real, c.real) && |
| equals(imaginary, c.imaginary); |
| } |
| return false; |
| } |
| |
| /** |
| * Gets a hash code for the complex number. |
| * |
| * <p>The behavior is the same as if the components of the complex number were passed |
| * to {@link java.util.Arrays#hashCode(double[]) Arrays.hashCode(double[])}: |
| * <pre> |
| * {@code Arrays.hashCode(new double[] {getReal(), getImaginary()})} |
| * </pre> |
| * |
| * @return A hash code value for this object. |
| * @see java.util.Arrays#hashCode(double[]) Arrays.hashCode(double[]) |
| */ |
| @Override |
| public int hashCode() { |
| return 31 * (31 + Double.hashCode(real)) + Double.hashCode(imaginary); |
| } |
| |
| /** |
| * Gets the imaginary part. |
| * |
| * @return The imaginary part. |
| */ |
| public double getImaginary() { |
| return imaginary; |
| } |
| |
| /** |
| * Gets the imaginary part (C++ grammar). |
| * |
| * @return The imaginary part. |
| * @see #getImaginary() |
| */ |
| public double imag() { |
| return getImaginary(); |
| } |
| |
| /** |
| * Gets the real part. |
| * |
| * @return The real part. |
| */ |
| public double getReal() { |
| return real; |
| } |
| |
| /** |
| * Gets the real part (C++ grammar). |
| * |
| * @return The real part. |
| * @see #getReal() |
| */ |
| public double real() { |
| return getReal(); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code this * factor}. |
| * Implements the formula: |
| * |
| * <p>\[ (a + i b)(c + i d) = (ac - bd) + i (ad + bc) \] |
| * |
| * <p>Recalculates to recover infinities as specified in C99 standard G.5.1. |
| * |
| * @param factor Value to be multiplied by this complex number. |
| * @return {@code this * factor}. |
| * @see <a href="http://mathworld.wolfram.com/ComplexMultiplication.html">Complex Muliplication</a> |
| */ |
| public Complex multiply(Complex factor) { |
| return multiply(real, imaginary, factor.real, factor.imaginary); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is: |
| * <pre> |
| * (a + i b)(c + i d) = (ac - bd) + i (ad + bc) |
| * </pre> |
| * |
| * <p>Recalculates to recover infinities as specified in C99 standard G.5.1. |
| * |
| * @param re1 Real component of first number. |
| * @param im1 Imaginary component of first number. |
| * @param re2 Real component of second number. |
| * @param im2 Imaginary component of second number. |
| * @return (a + b i)(c + d i). |
| */ |
| private static Complex multiply(double re1, double im1, double re2, double im2) { |
| double a = re1; |
| double b = im1; |
| double c = re2; |
| double d = im2; |
| final double ac = a * c; |
| final double bd = b * d; |
| final double ad = a * d; |
| final double bc = b * c; |
| double x = ac - bd; |
| double y = ad + bc; |
| |
| // -------------- |
| // NaN can occur if: |
| // - any of (a,b,c,d) are NaN (for NaN or Infinite complex numbers) |
| // - a multiplication of infinity by zero (ac,bd,ad,bc). |
| // - a subtraction of infinity from infinity (e.g. ac - bd) |
| // Note that (ac,bd,ad,bc) can be infinite due to overflow. |
| // |
| // Detect a NaN result and perform correction. |
| // |
| // Modification from the listing in ISO C99 G.5.1 (6) |
| // Do not correct infinity multiplied by zero. This is left as NaN. |
| // -------------- |
| |
| if (Double.isNaN(x) && Double.isNaN(y)) { |
| // Recover infinities that computed as NaN+iNaN ... |
| boolean recalc = false; |
| if ((Double.isInfinite(a) || Double.isInfinite(b)) && |
| isNotZero(c, d)) { |
| // This complex is infinite. |
| // "Box" the infinity and change NaNs in the other factor to 0. |
| a = boxInfinity(a); |
| b = boxInfinity(b); |
| c = changeNaNtoZero(c); |
| d = changeNaNtoZero(d); |
| recalc = true; |
| } |
| // (c, d) may have been corrected so do not use factor.isInfinite(). |
| if ((Double.isInfinite(c) || Double.isInfinite(d)) && |
| isNotZero(a, b)) { |
| // This other complex is infinite. |
| // "Box" the infinity and change NaNs in the other factor to 0. |
| c = boxInfinity(c); |
| d = boxInfinity(d); |
| a = changeNaNtoZero(a); |
| b = changeNaNtoZero(b); |
| recalc = true; |
| } |
| if (!recalc && (Double.isInfinite(ac) || Double.isInfinite(bd) || |
| Double.isInfinite(ad) || Double.isInfinite(bc))) { |
| // The result overflowed to infinity. |
| // Recover infinities from overflow by changing NaNs to 0 ... |
| a = changeNaNtoZero(a); |
| b = changeNaNtoZero(b); |
| c = changeNaNtoZero(c); |
| d = changeNaNtoZero(d); |
| recalc = true; |
| } |
| if (recalc) { |
| x = Double.POSITIVE_INFINITY * (a * c - b * d); |
| y = Double.POSITIVE_INFINITY * (a * d + b * c); |
| } |
| } |
| return new Complex(x, y); |
| } |
| |
| /** |
| * Box values for the real or imaginary component of an infinite complex number. |
| * Any infinite value will be returned as one. Non-infinite values will be returned as zero. |
| * The sign is maintained. |
| * |
| * <pre> |
| * inf = 1 |
| * -inf = -1 |
| * x = 0 |
| * -x = -0 |
| * </pre> |
| * |
| * @param component the component |
| * @return The boxed value |
| */ |
| private static double boxInfinity(double component) { |
| return Math.copySign(Double.isInfinite(component) ? 1.0 : 0.0, component); |
| } |
| |
| /** |
| * Checks if the complex number is not zero. |
| * |
| * @param real the real component |
| * @param imaginary the imaginary component |
| * @return true if the complex is not zero |
| */ |
| private static boolean isNotZero(double real, double imaginary) { |
| // The use of equals is deliberate. |
| // This method must distinguish NaN from zero thus ruling out: |
| // (real != 0.0 || imaginary != 0.0) |
| return !(real == 0.0 && imaginary == 0.0); |
| } |
| |
| /** |
| * Change NaN to zero preserving the sign; otherwise return the value. |
| * |
| * @param value the value |
| * @return The new value |
| */ |
| private static double changeNaNtoZero(double value) { |
| return Double.isNaN(value) ? Math.copySign(0.0, value) : value; |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code this * factor}, with {@code factor} |
| * interpreted as a real number. |
| * Implements the formula: |
| * |
| * <p>\[ (a + i b) c = (ac) + i (bc) \] |
| * |
| * <p>This method is included for compatibility with ISO C99 which defines arithmetic between |
| * real-only and complex numbers.</p> |
| * |
| * <p>Note: This method should be preferred over using |
| * {@link #multiply(Complex) multiply(Complex.ofCartesian(factor, 0))}. Multiplication |
| * can generate signed zeros if either {@code this} complex has zeros for the real |
| * and/or imaginary component, or if the factor is zero. The summation of signed zeros |
| * in {@link #multiply(Complex)} may create zeros in the result that differ in sign |
| * from the equivalent call to multiply by a real-only number. |
| * |
| * @param factor Value to be multiplied by this complex number. |
| * @return {@code this * factor}. |
| * @see #multiply(Complex) |
| */ |
| public Complex multiply(double factor) { |
| return new Complex(real * factor, imaginary * factor); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code this * factor}, with {@code factor} |
| * interpreted as an imaginary number. |
| * Implements the formula: |
| * |
| * <p>\[ (a + i b) id = (-bd) + i (ad) \] |
| * |
| * <p>This method can be used to compute the multiplication of this complex number \( z \) |
| * by \( i \). This should be used in preference to |
| * {@link #multiply(Complex) multiply(Complex.I)} with or without {@link #negate() negation}:</p> |
| * |
| * \[ iz = (-b + i a) \\ |
| * -iz = (b - i a) \] |
| * |
| * <p>This method is included for compatibility with ISO C99 which defines arithmetic between |
| * imaginary-only and complex numbers.</p> |
| * |
| * <p>Note: This method should be preferred over using |
| * {@link #multiply(Complex) multiply(Complex.ofCartesian(0, factor))}. Multiplication |
| * can generate signed zeros if either {@code this} complex has zeros for the real |
| * and/or imaginary component, or if the factor is zero. The summation of signed zeros |
| * in {@link #multiply(Complex)} may create zeros in the result that differ in sign |
| * from the equivalent call to multiply by an imaginary-only number. |
| * |
| * @param factor Value to be multiplied by this complex number. |
| * @return {@code this * factor}. |
| * @see #multiply(Complex) |
| */ |
| public Complex multiplyImaginary(double factor) { |
| return new Complex(-imaginary * factor, real * factor); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is the negation of both the real and imaginary parts |
| * of complex number \( z \). |
| * |
| * @return \( -z \). |
| */ |
| public Complex negate() { |
| return new Complex(-real, -imaginary); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code (this - subtrahend)}. |
| * Implements the formula: |
| * |
| * <p>\[ (a + i b) - (c + i d) = (a - c) + i (b - d) \] |
| * |
| * @param subtrahend Value to be subtracted from this complex number. |
| * @return {@code this - subtrahend}. |
| * @see <a href="http://mathworld.wolfram.com/ComplexSubtraction.html">Complex Subtraction</a> |
| */ |
| public Complex subtract(Complex subtrahend) { |
| return new Complex(real - subtrahend.real, |
| imaginary - subtrahend.imaginary); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code (this - subtrahend)}, |
| * with {@code subtrahend} interpreted as a real number. |
| * Implements the formula: |
| * |
| * <p>\[ (a + i b) - c = (a - c) + i b \] |
| * |
| * <p>This method is included for compatibility with ISO C99 which defines arithmetic between |
| * real-only and complex numbers.</p> |
| * |
| * @param subtrahend Value to be subtracted from this complex number. |
| * @return {@code this - subtrahend}. |
| * @see #subtract(Complex) |
| */ |
| public Complex subtract(double subtrahend) { |
| return new Complex(real - subtrahend, imaginary); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code (this - subtrahend)}, |
| * with {@code subtrahend} interpreted as an imaginary number. |
| * Implements the formula: |
| * |
| * <p>\[ (a + i b) - i d = a + i (b - d) \] |
| * |
| * <p>This method is included for compatibility with ISO C99 which defines arithmetic between |
| * imaginary-only and complex numbers.</p> |
| * |
| * @param subtrahend Value to be subtracted from this complex number. |
| * @return {@code this - subtrahend}. |
| * @see #subtract(Complex) |
| */ |
| public Complex subtractImaginary(double subtrahend) { |
| return new Complex(real, imaginary - subtrahend); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code (minuend - this)}, |
| * with {@code minuend} interpreted as a real number. |
| * Implements the formula: |
| * \[ c - (a + i b) = (c - a) - i b \] |
| * |
| * <p>This method is included for compatibility with ISO C99 which defines arithmetic between |
| * real-only and complex numbers.</p> |
| * |
| * <p>Note: This method inverts the sign of the imaginary component \( b \) if it is {@code 0.0}. |
| * The sign would not be inverted if subtracting from \( c + i 0 \) using |
| * {@link #subtract(Complex) Complex.ofCartesian(minuend, 0).subtract(this))} since |
| * {@code 0.0 - 0.0 = 0.0}. |
| * |
| * @param minuend Value this complex number is to be subtracted from. |
| * @return {@code minuend - this}. |
| * @see #subtract(Complex) |
| * @see #ofCartesian(double, double) |
| */ |
| public Complex subtractFrom(double minuend) { |
| return new Complex(minuend - real, -imaginary); |
| } |
| |
| /** |
| * Returns a {@code Complex} whose value is {@code (this - subtrahend)}, |
| * with {@code minuend} interpreted as an imaginary number. |
| * Implements the formula: |
| * \[ i d - (a + i b) = -a + i (d - b) \] |
| * |
| * <p>This method is included for compatibility with ISO C99 which defines arithmetic between |
| * imaginary-only and complex numbers.</p> |
| * |
| * <p>Note: This method inverts the sign of the real component \( a \) if it is {@code 0.0}. |
| * The sign would not be inverted if subtracting from \( 0 + i d \) using |
| * {@link #subtract(Complex) Complex.ofCartesian(0, minuend).subtract(this))} since |
| * {@code 0.0 - 0.0 = 0.0}. |
| * |
| * @param minuend Value this complex number is to be subtracted from. |
| * @return {@code this - subtrahend}. |
| * @see #subtract(Complex) |
| * @see #ofCartesian(double, double) |
| */ |
| public Complex subtractFromImaginary(double minuend) { |
| return new Complex(-real, minuend - imaginary); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/InverseCosine.html"> |
| * inverse cosine</a> of this complex number. |
| * |
| * <p>\[ \cos^{-1}(z) = \frac{\pi}{2} + i \left(\ln{iz + \sqrt{1 - z^2}}\right) \] |
| * |
| * <p>The inverse cosine of \( z \) is in the range \( [0, \infty) \) along the real axis and |
| * in the range \( [-\pi, \pi] \) along the imaginary axis. Special cases: |
| * |
| * <ul> |
| * <li>{@code z.conj().acos() == z.acos().conj()}. |
| * <li>If {@code z} is ±0 + i0, returns π/2 − i0. |
| * <li>If {@code z} is ±0 + iNaN, returns π/2 + iNaN. |
| * <li>If {@code z} is x + i∞ for finite x, returns π/2 − i∞. |
| * <li>If {@code z} is x + iNaN, returns NaN + iNaN. |
| * <li>If {@code z} is −∞ + iy for positive-signed finite y, returns π − i∞. |
| * <li>If {@code z} is +∞ + iy for positive-signed finite y, returns +0 − i∞. |
| * <li>If {@code z} is −∞ + i∞, returns 3π /4 − i∞. |
| * <li>If {@code z} is +∞ + i∞, returns π /4 − i∞. |
| * <li>If {@code z} is ±∞ + iNaN, returns NaN ± i∞ where the sign of the imaginary part of the result is unspecified. |
| * <li>If {@code z} is NaN + iy for finite y, returns NaN + iNaN. |
| * <li>If {@code z} is NaN + i∞, returns NaN − i∞. |
| * <li>If {@code z} is NaN + iNaN, returns NaN + iNaN. |
| * </ul> |
| * |
| * <p>This function is implemented using real \( x \) and imaginary \( y \) parts: |
| * |
| * <p>\[ \cos^{-1}(z) = \cos^{-1}(B) - i\ \text{sgn}(y) \ln\left(A + \sqrt{A^2-1}\right) \\ |
| * A = \frac{1}{2} \left[ \sqrt{(x+1)^2+y^2} + \sqrt{(x-1)^2+y^2} \right] \\ |
| * B = \frac{1}{2} \left[ \sqrt{(x+1)^2+y^2} - \sqrt{(x-1)^2+y^2} \right] \] |
| * |
| * <p>where \( \text{sgn}(y) \) is the sign function implemented using |
| * {@link Math#copySign(double,double) copySign(1.0, y)}. |
| * |
| * <p>The implementation is based on the method described in:</p> |
| * <blockquote> |
| * T E Hull, Thomas F Fairgrieve and Ping Tak Peter Tang (1997) |
| * Implementing the complex Arcsine and Arccosine Functions using Exception Handling. |
| * ACM Transactions on Mathematical Software, Vol 23, No 3, pp 299-335. |
| * </blockquote> |
| * |
| * <p>The code has been adapted from the <a href="https://www.boost.org/">Boost</a> |
| * {@code c++} implementation {@code <boost/math/complex/acos.hpp>}. The function is well |
| * defined over the entire complex number range, and produces accurate values even at the |
| * extremes due to special handling of overflow and underflow conditions.</p> |
| * |
| * @return The inverse cosine of this complex number. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/ArcCos/">ArcCos</a> |
| */ |
| public Complex acos() { |
| return acos(real, imaginary, Complex::ofCartesian); |
| } |
| |
| /** |
| * Returns the inverse cosine of the complex number. |
| * |
| * <p>This function exists to allow implementation of the identity |
| * {@code acosh(z) = +-i acos(z)}.<p> |
| * |
| * @param real Real part. |
| * @param imaginary Imaginary part. |
| * @param constructor Constructor. |
| * @return The inverse cosine of the complex number. |
| */ |
| private static Complex acos(final double real, final double imaginary, |
| final ComplexConstructor constructor) { |
| // Compute with positive values and determine sign at the end |
| final double x = Math.abs(real); |
| final double y = Math.abs(imaginary); |
| // The result (without sign correction) |
| double re; |
| double im; |
| |
| // Handle C99 special cases |
| if (isPosInfinite(x)) { |
| if (isPosInfinite(y)) { |
| re = PI_OVER_4; |
| im = y; |
| } else if (Double.isNaN(y)) { |
| // sign of the imaginary part of the result is unspecified |
| return constructor.create(imaginary, real); |
| } else { |
| re = 0; |
| im = Double.POSITIVE_INFINITY; |
| } |
| } else if (Double.isNaN(x)) { |
| if (isPosInfinite(y)) { |
| return constructor.create(x, -imaginary); |
| } |
| // No-use of the input constructor |
| return NAN; |
| } else if (isPosInfinite(y)) { |
| re = PI_OVER_2; |
| im = y; |
| } else if (Double.isNaN(y)) { |
| return constructor.create(x == 0 ? PI_OVER_2 : y, y); |
| } else { |
| // Special case for real numbers: |
| if (y == 0 && x <= 1) { |
| return constructor.create(x == 0 ? PI_OVER_2 : Math.acos(real), -imaginary); |
| } |
| |
| final double xp1 = x + 1; |
| final double xm1 = x - 1; |
| |
| if (inRegion(x, y, SAFE_MIN, SAFE_MAX)) { |
| final double yy = y * y; |
| final double r = Math.sqrt(xp1 * xp1 + yy); |
| final double s = Math.sqrt(xm1 * xm1 + yy); |
| final double a = 0.5 * (r + s); |
| final double b = x / a; |
| |
| if (b <= B_CROSSOVER) { |
| re = Math.acos(b); |
| } else { |
| final double apx = a + x; |
| if (x <= 1) { |
| re = Math.atan(Math.sqrt(0.5 * apx * (yy / (r + xp1) + (s - xm1))) / x); |
| } else { |
| re = Math.atan((y * Math.sqrt(0.5 * (apx / (r + xp1) + apx / (s + xm1)))) / x); |
| } |
| } |
| |
| if (a <= A_CROSSOVER) { |
| double am1; |
| if (x < 1) { |
| am1 = 0.5 * (yy / (r + xp1) + yy / (s - xm1)); |
| } else { |
| am1 = 0.5 * (yy / (r + xp1) + (s + xm1)); |
| } |
| im = Math.log1p(am1 + Math.sqrt(am1 * (a + 1))); |
| } else { |
| im = Math.log(a + Math.sqrt(a * a - 1)); |
| } |
| } else { |
| // Hull et al: Exception handling code from figure 6 |
| if (y <= (Precision.EPSILON * Math.abs(xm1))) { |
| if (x < 1) { |
| re = Math.acos(x); |
| im = y / Math.sqrt(xp1 * (1 - x)); |
| } else { |
| // This deviates from Hull et al's paper as per |
| // https://svn.boost.org/trac/boost/ticket/7290 |
| if ((Double.MAX_VALUE / xp1) > xm1) { |
| // xp1 * xm1 won't overflow: |
| re = y / Math.sqrt(xm1 * xp1); |
| im = Math.log1p(xm1 + Math.sqrt(xp1 * xm1)); |
| } else { |
| re = y / x; |
| im = LN_2 + Math.log(x); |
| } |
| } |
| } else if (y <= SAFE_MIN) { |
| // Hull et al: Assume x == 1. |
| // True if: |
| // E^2 > 8*sqrt(u) |
| // |
| // E = Machine epsilon: (1 + epsilon) = 1 |
| // u = Double.MIN_NORMAL |
| re = Math.sqrt(y); |
| im = Math.sqrt(y); |
| } else if (Precision.EPSILON * y - 1 >= x) { |
| re = PI_OVER_2; |
| im = LN_2 + Math.log(y); |
| } else if (x > 1) { |
| re = Math.atan(y / x); |
| final double xoy = x / y; |
| im = LN_2 + Math.log(y) + 0.5 * Math.log1p(xoy * xoy); |
| } else { |
| re = PI_OVER_2; |
| final double a = Math.sqrt(1 + y * y); |
| im = 0.5 * Math.log1p(2 * y * (y + a)); |
| } |
| } |
| } |
| |
| return constructor.create(negative(real) ? Math.PI - re : re, |
| negative(imaginary) ? im : -im); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/InverseSine.html"> |
| * inverse sine</a> of this complex number. |
| * |
| * <p>\[ \sin^{-1}(z) = - i \left(\ln{iz + \sqrt{1 - z^2}}\right) \] |
| * |
| * <p>The inverse sine of \( z \) is unbounded along the imaginary axis and |
| * in the range \( [-\pi, \pi] \) along the real axis. Special cases are handled |
| * as if the operation is implemented using \( \sin^{-1}(z) = -i \sinh^{-1}(iz) \). |
| * |
| * <p>This is implemented using real \( x \) and imaginary \( y \) parts: |
| * |
| * <p>\[ \sin^{-1}(z) = \sin^{-1}(B) + i\ \text{sgn}(y)\ln \left(A + \sqrt{A^2-1} \right) \\ |
| * A = \frac{1}{2} \left[ \sqrt{(x+1)^2+y^2} + \sqrt{(x-1)^2+y^2} \right] \\ |
| * B = \frac{1}{2} \left[ \sqrt{(x+1)^2+y^2} - \sqrt{(x-1)^2+y^2} \right] \] |
| * |
| * <p>where \( \text{sgn}(y) \) is the sign function implemented using |
| * {@link Math#copySign(double,double) copySign(1.0, y)}. |
| * |
| * <p>The implementation is based on the method described in:</p> |
| * <blockquote> |
| * T E Hull, Thomas F Fairgrieve and Ping Tak Peter Tang (1997) |
| * Implementing the complex Arcsine and Arccosine Functions using Exception Handling. |
| * ACM Transactions on Mathematical Software, Vol 23, No 3, pp 299-335. |
| * </blockquote> |
| * |
| * <p>The code has been adapted from the <a href="https://www.boost.org/">Boost</a> |
| * {@code c++} implementation {@code <boost/math/complex/asin.hpp>}. The function is well |
| * defined over the entire complex number range, and produces accurate values even at the |
| * extremes due to special handling of overflow and underflow conditions.</p> |
| * |
| * @return The inverse sine of this complex number. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/ArcSin/">ArcSin</a> |
| */ |
| public Complex asin() { |
| return asin(real, imaginary, Complex::ofCartesian); |
| } |
| |
| /** |
| * Returns the inverse sine of the complex number. |
| * |
| * <p>This function exists to allow implementation of the identity |
| * {@code asinh(z) = -i asin(iz)}.<p> |
| * |
| * <p>The code has been adapted from the <a href="https://www.boost.org/">Boost</a> |
| * {@code c++} implementation {@code <boost/math/complex/asin.hpp>}.</p> |
| * |
| * @param real Real part. |
| * @param imaginary Imaginary part. |
| * @param constructor Constructor. |
| * @return The inverse sine of this complex number. |
| */ |
| private static Complex asin(final double real, final double imaginary, |
| final ComplexConstructor constructor) { |
| // Compute with positive values and determine sign at the end |
| final double x = Math.abs(real); |
| final double y = Math.abs(imaginary); |
| // The result (without sign correction) |
| double re; |
| double im; |
| |
| // Handle C99 special cases |
| if (Double.isNaN(x)) { |
| if (isPosInfinite(y)) { |
| re = x; |
| im = y; |
| } else { |
| // No-use of the input constructor |
| return NAN; |
| } |
| } else if (Double.isNaN(y)) { |
| if (x == 0) { |
| re = 0; |
| im = y; |
| } else if (isPosInfinite(x)) { |
| re = y; |
| im = x; |
| } else { |
| // No-use of the input constructor |
| return NAN; |
| } |
| } else if (isPosInfinite(x)) { |
| re = isPosInfinite(y) ? PI_OVER_4 : PI_OVER_2; |
| im = x; |
| } else if (isPosInfinite(y)) { |
| re = 0; |
| im = y; |
| } else { |
| // Special case for real numbers: |
| if (y == 0 && x <= 1) { |
| return constructor.create(Math.asin(real), imaginary); |
| } |
| |
| final double xp1 = x + 1; |
| final double xm1 = x - 1; |
| |
| if (inRegion(x, y, SAFE_MIN, SAFE_MAX)) { |
| final double yy = y * y; |
| final double r = Math.sqrt(xp1 * xp1 + yy); |
| final double s = Math.sqrt(xm1 * xm1 + yy); |
| final double a = 0.5 * (r + s); |
| final double b = x / a; |
| |
| if (b <= B_CROSSOVER) { |
| re = Math.asin(b); |
| } else { |
| final double apx = a + x; |
| if (x <= 1) { |
| re = Math.atan(x / Math.sqrt(0.5 * apx * (yy / (r + xp1) + (s - xm1)))); |
| } else { |
| re = Math.atan(x / (y * Math.sqrt(0.5 * (apx / (r + xp1) + apx / (s + xm1))))); |
| } |
| } |
| |
| if (a <= A_CROSSOVER) { |
| double am1; |
| if (x < 1) { |
| am1 = 0.5 * (yy / (r + xp1) + yy / (s - xm1)); |
| } else { |
| am1 = 0.5 * (yy / (r + xp1) + (s + xm1)); |
| } |
| im = Math.log1p(am1 + Math.sqrt(am1 * (a + 1))); |
| } else { |
| im = Math.log(a + Math.sqrt(a * a - 1)); |
| } |
| } else { |
| // Hull et al: Exception handling code from figure 4 |
| if (y <= (Precision.EPSILON * Math.abs(xm1))) { |
| if (x < 1) { |
| re = Math.asin(x); |
| im = y / Math.sqrt(xp1 * (1 - x)); |
| } else { |
| re = PI_OVER_2; |
| if ((Double.MAX_VALUE / xp1) > xm1) { |
| // xp1 * xm1 won't overflow: |
| im = Math.log1p(xm1 + Math.sqrt(xp1 * xm1)); |
| } else { |
| im = LN_2 + Math.log(x); |
| } |
| } |
| } else if (y <= SAFE_MIN) { |
| // Hull et al: Assume x == 1. |
| // True if: |
| // E^2 > 8*sqrt(u) |
| // |
| // E = Machine epsilon: (1 + epsilon) = 1 |
| // u = Double.MIN_NORMAL |
| re = PI_OVER_2 - Math.sqrt(y); |
| im = Math.sqrt(y); |
| } else if (Precision.EPSILON * y - 1 >= x) { |
| // Possible underflow: |
| re = x / y; |
| im = LN_2 + Math.log(y); |
| } else if (x > 1) { |
| re = Math.atan(x / y); |
| final double xoy = x / y; |
| im = LN_2 + Math.log(y) + 0.5 * Math.log1p(xoy * xoy); |
| } else { |
| final double a = Math.sqrt(1 + y * y); |
| // Possible underflow: |
| re = x / a; |
| im = 0.5 * Math.log1p(2 * y * (y + a)); |
| } |
| } |
| } |
| |
| return constructor.create(changeSign(re, real), |
| changeSign(im, imaginary)); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/InverseTangent.html"> |
| * inverse tangent</a> of this complex number. |
| * |
| * <p>\[ \tan^{-1}(z) = \frac{i}{2} \ln \left( \frac{i + z}{i - z} \right) \] |
| * |
| * <p>As per the C99 standard this function is computed using the trigonomic identity: |
| * \[ \tan^{-1}(z) = -i \tanh^{-1}(iz) \] |
| * |
| * @return The inverse tangent of this complex number. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/ArcTan/">ArcTan</a> |
| */ |
| public Complex atan() { |
| // Define in terms of atanh |
| // atan(z) = -i atanh(iz) |
| // Multiply this number by I, compute atanh, then multiply by back |
| return atanh(-imaginary, real, Complex::multiplyNegativeI); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/InverseHyperbolicSine.html"> |
| * inverse hyperbolic sine</a> of this complex number. |
| * |
| * <p>\[ \sinh^{-1}(z) = \ln \left(z + \sqrt{1 + z^2} \right) \] |
| * |
| * <p>The inverse hyperbolic sine of \( z \) is unbounded along the real axis and |
| * in the range \( [-\pi, \pi] \) along the imaginary axis. Special cases: |
| * |
| * <ul> |
| * <li>{@code z.conj().asinh() == z.asinh().conj()}. |
| * <li>This is an odd function: \( \sinh^{-1}(z) = -\sinh^{-1}(-z) \). |
| * <li>If {@code z} is +0 + i0, returns 0 + i0. |
| * <li>If {@code z} is x + i∞ for positive-signed finite x, returns +∞ + iπ/2. |
| * <li>If {@code z} is x + iNaN for finite x, returns NaN + iNaN. |
| * <li>If {@code z} is +∞ + iy for positive-signed finite y, returns +∞ + i0. |
| * <li>If {@code z} is +∞ + i∞, returns +∞ + iπ/4. |
| * <li>If {@code z} is +∞ + iNaN, returns +∞ + iNaN. |
| * <li>If {@code z} is NaN + i0, returns NaN + i0. |
| * <li>If {@code z} is NaN + iy for finite nonzero y, returns NaN + iNaN. |
| * <li>If {@code z} is NaN + i∞, returns ±∞ + iNaN (where the sign of the real part of the result is unspecified). |
| * <li>If {@code z} is NaN + iNaN, returns NaN + iNaN. |
| * </ul> |
| * |
| * <p>This function is computed using the trigonomic identity: |
| * |
| * <p>\[ \sinh^{-1}(z) = -i \sin^{-1}(iz) \] |
| * |
| * @return The inverse hyperbolic sine of this complex number. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/ArcSinh/">ArcSinh</a> |
| */ |
| public Complex asinh() { |
| // Define in terms of asin |
| // asinh(z) = -i asin(iz) |
| // Note: This is the opposite to the identity defined in the C99 standard: |
| // asin(z) = -i asinh(iz) |
| // Multiply this number by I, compute asin, then multiply by back |
| return asin(-imaginary, real, Complex::multiplyNegativeI); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/InverseHyperbolicTangent.html"> |
| * inverse hyperbolic tangent</a> of this complex number. |
| * |
| * <p>\[ \tanh^{-1}(z) = \frac{1}{2} \ln \left( \frac{1 + z}{1 - z} \right) \] |
| * |
| * <p>The inverse hyperbolic tangent of \( z \) is unbounded along the real axis and |
| * in the range \( [-\pi, \pi] \) along the imaginary axis. Special cases: |
| * |
| * <ul> |
| * <li>{@code z.conj().atanh() == z.atanh().conj()}. |
| * <li>This is an odd function: \( \tanh^{-1}(z) = -\tanh^{-1}(-z) \). |
| * <li>If {@code z} is +0 + i0, returns +0 + i0. |
| * <li>If {@code z} is +0 + iNaN, returns +0 + iNaN. |
| * <li>If {@code z} is +1 + i0, returns +∞ + i0. |
| * <li>If {@code z} is x + i∞ for finite positive-signed x, returns +0 + iπ /2. |
| * <li>If {@code z} is x+iNaN for nonzero finite x, returns NaN+iNaN. |
| * <li>If {@code z} is +∞ + iy for finite positive-signed y, returns +0 + iπ /2. |
| * <li>If {@code z} is +∞ + i∞, returns +0 + iπ /2. |
| * <li>If {@code z} is +∞ + iNaN, returns +0 + iNaN. |
| * <li>If {@code z} is NaN+iy for finite y, returns NaN+iNaN. |
| * <li>If {@code z} is NaN + i∞, returns ±0 + iπ /2 (where the sign of the real part of the result is unspecified). |
| * <li>If {@code z} is NaN + iNaN, returns NaN + iNaN. |
| * </ul> |
| * |
| * <p>This is implemented using real \( x \) and imaginary \( y \) parts: |
| * |
| * <p>\[ \tanh^{-1}(z) = \frac{1}{4} \ln \left(1 + \frac{4x}{(1-x)^2+y^2} \right) + \\ |
| * i \frac{1}{2} \left( \tan^{-1} \left(\frac{2y}{1-x^2-y^2} \right) + \frac{\pi}{2} \left(\text{sgn}(x^2+y^2-1)+1 \right) \text{sgn}(y) \right) \] |
| * |
| * <p>The imaginary part is computed using {@link Math#atan2(double, double)} to ensure the |
| * correct quadrant is returned from \( \tan^{-1} \left(\frac{2y}{1-x^2-y^2} \right) \). |
| * |
| * <p>The code has been adapted from the <a href="https://www.boost.org/">Boost</a> |
| * {@code c++} implementation {@code <boost/math/complex/atanh.hpp>}. The function is well |
| * defined over the entire complex number range, and produces accurate values even at the |
| * extremes due to special handling of overflow and underflow conditions. |
| * |
| * @return The inverse hyperbolic tangent of this complex number. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/ArcTanh/">ArcTanh</a> |
| */ |
| public Complex atanh() { |
| return atanh(real, imaginary, Complex::ofCartesian); |
| } |
| |
| /** |
| * Returns the inverse hyperbolic tangent of this complex number. |
| * |
| * <p>This function exists to allow implementation of the identity |
| * {@code atan(z) = -i atanh(iz)}.<p> |
| * |
| * @param real Real part. |
| * @param imaginary Imaginary part. |
| * @param constructor Constructor. |
| * @return The inverse hyperbolic tangent of the complex number. |
| */ |
| private static Complex atanh(final double real, final double imaginary, |
| final ComplexConstructor constructor) { |
| // Compute with positive values and determine sign at the end |
| final double x = Math.abs(real); |
| final double y = Math.abs(imaginary); |
| // The result (without sign correction) |
| double re; |
| double im; |
| |
| // Handle C99 special cases |
| if (Double.isNaN(x)) { |
| if (isPosInfinite(y)) { |
| // The sign of the real part of the result is unspecified |
| return constructor.create(0, Math.copySign(PI_OVER_2, imaginary)); |
| } |
| // No-use of the input constructor. |
| // Optionally raises the ‘‘invalid’’ floating-point exception, for finite y. |
| return NAN; |
| } else if (Double.isNaN(y)) { |
| if (isPosInfinite(x)) { |
| return constructor.create(Math.copySign(0, real), Double.NaN); |
| } |
| if (x == 0) { |
| return constructor.create(real, Double.NaN); |
| } |
| // No-use of the input constructor |
| return NAN; |
| } else { |
| // x && y are finite or infinite. |
| |
| // Check the safe region. |
| // The lower and upper bounds have been copied from boost::math::atanh. |
| // They are different from the safe region for asin and acos. |
| // x >= SAFE_UPPER: (1-x) == -x |
| // x <= SAFE_LOWER: 1 - x^2 = 1 |
| |
| if (inRegion(x, y, SAFE_LOWER, SAFE_UPPER)) { |
| // Normal computation within a safe region. |
| |
| // minus x plus 1: (-x+1) |
| final double mxp1 = 1 - x; |
| final double yy = y * y; |
| // The definition of real component is: |
| // real = log( ((x+1)^2+y^2) / ((1-x)^2+y^2) ) / 4 |
| // This simplifies by adding 1 and subtracting 1 as a fraction: |
| // = log(1 + ((x+1)^2+y^2) / ((1-x)^2+y^2) - ((1-x)^2+y^2)/((1-x)^2+y^2) ) / 4 |
| // |
| // real(atanh(z)) == log(1 + 4*x / ((1-x)^2+y^2)) / 4 |
| // imag(atanh(z)) == tan^-1 (2y, (1-x)(1+x) - y^2) / 2 |
| // The division is done at the end of the function. |
| re = Math.log1p(4 * x / (mxp1 * mxp1 + yy)); |
| im = Math.atan2(2 * y, mxp1 * (1 + x) - yy); |
| } else { |
| // This section handles exception cases that would normally cause |
| // underflow or overflow in the main formulas. |
| |
| // C99. G.7: Special case for imaginary only numbers |
| if (x == 0) { |
| if (imaginary == 0) { |
| return constructor.create(real, imaginary); |
| } |
| // atanh(iy) = i atan(y) |
| return constructor.create(real, Math.atan(imaginary)); |
| } |
| |
| // Real part: |
| // real = Math.log1p(4x / ((1-x)^2 + y^2)) |
| // real = Math.log1p(4x / (1 - 2x + x^2 + y^2)) |
| // real = Math.log1p(4x / (1 + x(x-2) + y^2)) |
| // without either overflow or underflow in the squared terms. |
| if (x >= SAFE_UPPER) { |
| // (1-x) = -x to machine precision: |
| // log1p(4x / (x^2 + y^2)) |
| if (isPosInfinite(x) || isPosInfinite(y)) { |
| re = 0; |
| } else if (y >= SAFE_UPPER) { |
| // Big x and y: divide by x*y |
| re = Math.log1p((4 / y) / (x / y + y / x)); |
| } else if (y > 1) { |
| // Big x: divide through by x: |
| re = Math.log1p(4 / (x + y * y / x)); |
| } else { |
| // Big x small y, as above but neglect y^2/x: |
| re = Math.log1p(4 / x); |
| } |
| } else if (y >= SAFE_UPPER) { |
| if (x > 1) { |
| // Big y, medium x, divide through by y: |
| final double mxp1 = 1 - x; |
| re = Math.log1p((4 * x / y) / (mxp1 * mxp1 / y + y)); |
| } else { |
| // Big y, small x, as above but neglect (1-x)^2/y: |
| // Note: log1p(v) == v - v^2/2 + v^3/3 ... Taylor series when v is small. |
| // Here v is so small only the first term matters. |
| re = 4 * x / y / y; |
| } |
| } else if (x == 1) { |
| // x = 1, small y: |
| // Special case when x == 1 as (1-x) is invalid. |
| // Simplify the following formula: |
| // real = log( sqrt((x+1)^2+y^2) ) / 2 - log( sqrt((1-x)^2+y^2) ) / 2 |
| // = log( sqrt(4+y^2) ) / 2 - log(y) / 2 |
| // if: 4+y^2 -> 4 |
| // = log( 2 ) / 2 - log(y) / 2 |
| // = (log(2) - log(y)) / 2 |
| // Multiply by 2 as it will be divided by 4 at the end. |
| // C99: if y=0 raises the ‘‘divide-by-zero’’ floating-point exception. |
| re = 2 * (LN_2 - Math.log(y)); |
| } else { |
| // Modified from boost which checks y > SAFE_LOWER. |
| // if y*y -> 0 it will be ignored so always include it. |
| final double mxp1 = 1 - x; |
| re = Math.log1p((4 * x) / (mxp1 * mxp1 + y * y)); |
| } |
| |
| // Imaginary part: |
| // imag = atan2(2y, (1-x)(1+x) - y^2) |
| // if x or y are large, then the formula: |
| // atan2(2y, (1-x)(1+x) - y^2) |
| // evaluates to +(PI - theta) where theta is negligible compared to PI. |
| if ((x >= SAFE_UPPER) || (y >= SAFE_UPPER)) { |
| im = Math.PI; |
| } else if (x <= SAFE_LOWER) { |
| // (1-x)^2 -> 1 |
| if (y <= SAFE_LOWER) { |
| // 1 - y^2 -> 1 |
| im = Math.atan2(2 * y, 1); |
| } else { |
| im = Math.atan2(2 * y, 1 - y * y); |
| } |
| } else { |
| // Medium x, small y. |
| // Modified from boost which checks (y == 0) && (x == 1) and sets re = 0. |
| // This is same as the result from calling atan2(0, 0) so just do that. |
| // 1 - y^2 = 1 so ignore subtracting y^2 |
| im = Math.atan2(2 * y, (1 - x) * (1 + x)); |
| } |
| } |
| } |
| |
| re /= 4; |
| im /= 2; |
| return constructor.create(changeSign(re, real), |
| changeSign(im, imaginary)); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/InverseHyperbolicCosine.html"> |
| * inverse hyperbolic cosine</a> of this complex number. |
| * |
| * <p>\[ \cosh^{-1}(z) = \ln \left(z + \sqrt{z + 1} \sqrt{z - 1} \right) \] |
| * |
| * <p>The inverse hyperbolic cosine of \( z \) is in the range \( [0, \infty) \) along the real axis and |
| * in the range \( [-\pi, \pi] \) along the imaginary axis. Special cases: |
| * |
| * <ul> |
| * <li>{@code z.conj().acosh() == z.acosh().conj()}. |
| * <li>If {@code z} is ±0 + i0, returns +0 + iπ/2. |
| * <li>If {@code z} is x + i∞ for finite x, returns +∞ + iπ/2. |
| * <li>If {@code z} is x + iNaN for finite x, returns NaN + iNaN. |
| * <li>If {@code z} is −∞ + iy for positive-signed finite y, returns +∞ + iπ. |
| * <li>If {@code z} is +∞ + iy for positive-signed finite y, returns +∞ + i0. |
| * <li>If {@code z} is −∞ + i∞, returns +∞ + i3π/4. |
| * <li>If {@code z} is +∞ + i∞, returns +∞ + iπ/4. |
| * <li>If {@code z} is ±∞ + iNaN, returns +∞ + iNaN. |
| * <li>If {@code z} is NaN + iy for finite y, returns NaN + iNaN. |
| * <li>If {@code z} is NaN + i∞, returns +∞ + iNaN. |
| * <li>If {@code z} is NaN + iNaN, returns NaN + iNaN. |
| * </ul> |
| * |
| * <p>This function is computed using the trigonomic identity: |
| * |
| * <p>\[ \cosh^{-1}(z) = \pm i \cos^{-1}(z) \] |
| * |
| * <p>The sign of the multiplier is chosen to give {@code z.acosh().real() >= 0} |
| * and compatibility with the C99 standard. |
| * |
| * @return The inverse hyperbolic cosine of this complex number. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/ArcCosh/">ArcCosh</a> |
| */ |
| public Complex acosh() { |
| // Define in terms of acos |
| // acosh(z) = +-i acos(z) |
| // Handle special case: |
| // acos(+-0 + iNaN) = π/2 + iNaN |
| // acosh(x + iNaN) = NaN + iNaN for all finite x (including zero) |
| if (Double.isNaN(imaginary) && Double.isFinite(real)) { |
| return NAN; |
| } |
| return acos(real, imaginary, (re, im) -> |
| // Set the sign appropriately for real >= 0 |
| (negative(im)) ? |
| // Multiply by I |
| new Complex(-im, re) : |
| // Multiply by -I |
| new Complex(im, -re) |
| ); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/Cosine.html"> |
| * cosine</a> of this complex number. |
| * |
| * <p>\[ \cos(z) = \frac{1}{2} \left( e^{iz} + e^{-iz} \right) \] |
| * |
| * <p>This is an even function: \( \cos(z) = \cos(-z) \). |
| * |
| * <p>This is implemented using real \( x \) and imaginary \( y \) parts: |
| * |
| * <p>\[ \cos(x + iy) = \cos(x)\cosh(y) - i \sin(x)\sinh(y) \] |
| * |
| * <p>As per the C99 standard this function is computed using the trigonomic identity: |
| * |
| * <p>\[ cos(z) = cosh(iz) \] |
| * |
| * @return The cosine of this complex number. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/Cos/">Cos</a> |
| */ |
| public Complex cos() { |
| // Define in terms of cosh |
| // cos(z) = cosh(iz) |
| // Multiply this number by I and compute cosh. |
| return cosh(-imaginary, real, Complex::ofCartesian); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/HyperbolicCosine.html"> |
| * hyperbolic cosine</a> of this complex number. |
| * |
| * <p>\[ \cosh(z) = \frac{1}{2} \left( e^{z} + e^{-z} \right) \] |
| * |
| * <p>The hyperbolic cosine of \( z \) is an entire function in the complex plane. |
| * and is periodic with respect to the imaginary component with period \( 2\pi i \). |
| * |
| * <ul> |
| * <li>{@code z.conj().cosh() == z.cosh().conj()}. |
| * <li>This is an even function: \( \cosh(z) = \cosh(-z) \). |
| * <li>If {@code z} is +0 + i0, returns 1 + i0. |
| * <li>If {@code z} is +0 + i∞, returns NaN ± i0 (where the sign of the imaginary part of the result is unspecified). |
| * <li>If {@code z} is +0 + iNaN, returns NaN ± i0 (where the sign of the imaginary part of the result is unspecified). |
| * <li>If {@code z} is x + i∞ for finite nonzero x, returns NaN + iNaN. |
| * <li>If {@code z} is x + iNaN for finite nonzero x, returns NaN + iNaN. |
| * <li>If {@code z} is +∞ + i0, returns +∞ + i0. |
| * <li>If {@code z} is +∞ + iy for finite nonzero y, returns +∞ cis(y) (see {@link #ofCis(double)}). |
| * <li>If {@code z} is +∞ + i∞, returns ±∞ + iNaN (where the sign of the real part of the result is unspecified). |
| * <li>If {@code z} is +∞ + iNaN, returns +∞ + iNaN. |
| * <li>If {@code z} is NaN + i0, returns NaN ± i0 (where the sign of the imaginary part of the result is unspecified). |
| * <li>If {@code z} is NaN + iy for all nonzero numbers y, returns NaN + iNaN. |
| * <li>If {@code z} is NaN + iNaN, returns NaN + iNaN. |
| * </ul> |
| * |
| * <p>This is implemented using real \( x \) and imaginary \( y \) parts: |
| * |
| * <p>\[ \cosh(x + iy) = \cosh(x)\cos(y) + i \sinh(x)\sin(y) \] |
| * |
| * @return The hyperbolic cosine of this complex number. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/Cosh/">Cosh</a> |
| */ |
| public Complex cosh() { |
| return cosh(real, imaginary, Complex::ofCartesian); |
| } |
| |
| /** |
| * Returns the hyperbolic cosine of the complex number. |
| * |
| * <p>This function exists to allow implementation of the identity |
| * {@code cos(z) = cosh(iz)}.<p> |
| * |
| * @param real Real part. |
| * @param imaginary Imaginary part. |
| * @param constructor Constructor. |
| * @return The hyperbolic cosine of the complex number. |
| */ |
| private static Complex cosh(double real, double imaginary, ComplexConstructor constructor) { |
| // ISO C99: Preserve the even function by mapping to positive |
| // f(z) = f(-z) |
| if (Double.isInfinite(real) && !Double.isFinite(imaginary)) { |
| return constructor.create(Math.abs(real), Double.NaN); |
| } |
| if (real == 0 && !Double.isFinite(imaginary)) { |
| return constructor.create(Double.NaN, changeSign(real, imaginary)); |
| } |
| if (real == 0 && imaginary == 0) { |
| return constructor.create(1, changeSign(real, imaginary)); |
| } |
| if (imaginary == 0 && !Double.isFinite(real)) { |
| return constructor.create(Math.abs(real), changeSign(imaginary, real)); |
| } |
| return constructor.create(Math.cosh(real) * Math.cos(imaginary), |
| Math.sinh(real) * Math.sin(imaginary)); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/ExponentialFunction.html"> |
| * exponential function</a> of this complex number. |
| * |
| * <p>\[ \exp(z) = e^z \] |
| * |
| * <p>The exponential function of \( z \) is an entire function in the complex plane. |
| * Special cases: |
| * |
| * <ul> |
| * <li>{@code z.conj().exp() == z.exp().conj()}. |
| * <li>If {@code z} is ±0 + i0, returns 1 + i0. |
| * <li>If {@code z} is x + i∞ for finite x, returns NaN + iNaN. |
| * <li>If {@code z} is x + iNaN for finite x, returns NaN + iNaN. |
| * <li>If {@code z} is +∞ + i0, returns +∞ + i0. |
| * <li>If {@code z} is −∞ + iy for finite y, returns +0 cis(y) (see {@link #ofCis(double)}). |
| * <li>If {@code z} is +∞ + iy for finite nonzero y, returns +∞ cis(y). |
| * <li>If {@code z} is −∞ + i∞, returns ±0 ± i0 (where the signs of the real and imaginary parts of the result are unspecified). |
| * <li>If {@code z} is +∞ + i∞, returns ±∞ + iNaN (where the sign of the real part of the result is unspecified). |
| * <li>If {@code z} is −∞ + iNaN, returns ±0 ± i0 (where the signs of the real and imaginary parts of the result are unspecified). |
| * <li>If {@code z} is +∞ + iNaN, returns ±∞ + iNaN (where the sign of the real part of the result is unspecified). |
| * <li>If {@code z} is NaN + i0, returns NaN + i0. |
| * <li>If {@code z} is NaN + iy for all nonzero numbers y, returns NaN + iNaN. |
| * <li>If {@code z} is NaN + iNaN, returns NaN + iNaN. |
| * </ul> |
| * |
| * <p>Implements the formula: |
| * |
| * <p>\[ \exp(x + iy) = e^x (\cos(y) + i \sin(y)) \] |
| * |
| * @return <code>e<sup>this</sup></code>. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/Exp/">Exp</a> |
| */ |
| public Complex exp() { |
| if (Double.isInfinite(real)) { |
| // Set the scale factor applied to cis(y) |
| double zeroOrInf; |
| if (real < 0) { |
| if (!Double.isFinite(imaginary)) { |
| // (−∞ + i∞) or (−∞ + iNaN) returns (±0 ± i0) (where the signs of the |
| // real and imaginary parts of the result are unspecified). |
| // Here we preserve the conjugate equality. |
| return new Complex(0, Math.copySign(0, imaginary)); |
| } |
| // (−∞ + iy) returns +0 cis(y), for finite y |
| zeroOrInf = 0; |
| } else { |
| // (+∞ + i0) returns +∞ + i0. |
| if (imaginary == 0) { |
| return this; |
| } |
| // (+∞ + i∞) or (+∞ + iNaN) returns (±∞ + iNaN) and raises the invalid |
| // floating-point exception (where the sign of the real part of the |
| // result is unspecified). |
| if (!Double.isFinite(imaginary)) { |
| return new Complex(real, Double.NaN); |
| } |
| // (+∞ + iy) returns (+∞ cis(y)), for finite nonzero y. |
| zeroOrInf = real; |
| } |
| return new Complex(zeroOrInf * Math.cos(imaginary), |
| zeroOrInf * Math.sin(imaginary)); |
| } else if (Double.isNaN(real)) { |
| // (NaN + i0) returns (NaN + i0); |
| // (NaN + iy) returns (NaN + iNaN) and optionally raises the invalid floating-point exception |
| // (NaN + iNaN) returns (NaN + iNaN) |
| return imaginary == 0 ? this : NAN; |
| } else if (!Double.isFinite(imaginary)) { |
| // (x + i∞) or (x + iNaN) returns (NaN + iNaN) and raises the invalid |
| // floating-point exception, for finite x. |
| return NAN; |
| } |
| // real and imaginary are finite. |
| // Compute e^a * (cos(b) + i sin(b)). |
| |
| // Special case: |
| // (±0 + i0) returns (1 + i0) |
| final double exp = Math.exp(real); |
| if (imaginary == 0) { |
| return new Complex(exp, imaginary); |
| } |
| return new Complex(exp * Math.cos(imaginary), |
| exp * Math.sin(imaginary)); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/NaturalLogarithm.html"> |
| * natural logarithm</a> of this complex number. |
| * |
| * <p>The natural logarithm of \( z \) is unbounded along the real axis and |
| * in the range \( [-\pi, \pi] \) along the imaginary axis. Special cases: |
| * |
| * <ul> |
| * <li>{@code z.conj().log() == z.log().conj()}. |
| * <li>If {@code z} is −0 + i0, returns −∞ + iπ. |
| * <li>If {@code z} is +0 + i0, returns −∞ + i0. |
| * <li>If {@code z} is x + i∞ for finite x, returns +∞ + iπ/2. |
| * <li>If {@code z} is x + iNaN for finite x, returns NaN + iNaN. |
| * <li>If {@code z} is −∞ + iy for finite positive-signed y, returns +∞ + iπ. |
| * <li>If {@code z} is +∞ + iy for finite positive-signed y, returns +∞ + i0. |
| * <li>If {@code z} is −∞ + i∞, returns +∞ + i3π/4. |
| * <li>If {@code z} is +∞ + i∞, returns +∞ + iπ/4. |
| * <li>If {@code z} is ±∞ + iNaN, returns +∞ + iNaN. |
| * <li>If {@code z} is NaN + iy for finite y, returns NaN + iNaN. |
| * <li>If {@code z} is NaN + i∞, returns +∞ + iNaN. |
| * <li>If {@code z} is NaN + iNaN, returns NaN + iNaN. |
| * </ul> |
| * |
| * <p>Implements the formula: |
| * |
| * <p>\[ \ln(z) = \ln |z| + i \arg(z) \] |
| * |
| * <p>where \( |z| \) is the absolute and \( \arg(z) \) is the argument. |
| * |
| * <p>The implementation is based on the method described in:</p> |
| * <blockquote> |
| * T E Hull, Thomas F Fairgrieve and Ping Tak Peter Tang (1994) |
| * Implementing complex elementary functions using exception handling. |
| * ACM Transactions on Mathematical Software, Vol 20, No 2, pp 215-244. |
| * </blockquote> |
| * |
| * @return The natural logarithm of this complex number. |
| * @see Math#log(double) |
| * @see #abs() |
| * @see #arg() |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/Log/">Log</a> |
| */ |
| public Complex log() { |
| return log(Math::log, HALF, LN_2, Complex::ofCartesian); |
| } |
| |
| /** |
| * Returns the base 10 |
| * <a href="http://mathworld.wolfram.com/CommonLogarithm.html"> |
| * common logarithm</a> of this complex number. |
| * |
| * <p>The common logarithm of \( z \) is unbounded along the real axis and |
| * in the range \( [-\pi, \pi] \) along the imaginary axis. Special cases are as |
| * defined in the {@link #log() natural logarithm}: |
| * |
| * <p>Implements the formula: |
| * |
| * <p>\[ \log_{10}(z) = \log_{10} |z| + i \arg(z) \] |
| * |
| * <p>where \( |z| \) is the absolute and \( \arg(z) \) is the argument. |
| * |
| * @return The base 10 logarithm of this complex number. |
| * @see Math#log10(double) |
| * @see #abs() |
| * @see #arg() |
| */ |
| public Complex log10() { |
| return log(Math::log10, LOG_10E_O_2, LOG10_2, Complex::ofCartesian); |
| } |
| |
| /** |
| * Returns the logarithm of this complex number using the provided function. |
| * Implements the formula: |
| * <pre> |
| * log(x + i y) = log(|x + i y|) + i arg(x + i y) |
| * </pre> |
| * |
| * <p>Warning: The argument {@code logOf2} must be equal to {@code log(2)} using the |
| * provided log function otherwise scaling using powers of 2 in the case of overflow |
| * will be incorrect. This is provided as an internal optimisation. |
| * |
| * @param log Log function. |
| * @param logOfeOver2 The log function applied to e, then divided by 2. |
| * @param logOf2 The log function applied to 2. |
| * @param constructor Constructor for the returned complex. |
| * @return The logarithm of this complex number. |
| * @see #abs() |
| * @see #arg() |
| */ |
| private Complex log(UnaryOperation log, double logOfeOver2, double logOf2, ComplexConstructor constructor) { |
| // Handle NaN |
| if (Double.isNaN(real) || Double.isNaN(imaginary)) { |
| // Return NaN unless infinite |
| if (isInfinite()) { |
| return constructor.create(Double.POSITIVE_INFINITY, Double.NaN); |
| } |
| // No-use of the input constructor |
| return NAN; |
| } |
| |
| // Returns the real part: |
| // log(sqrt(x^2 + y^2)) |
| // log(x^2 + y^2) / 2 |
| |
| // Compute with positive values |
| double x = Math.abs(real); |
| double y = Math.abs(imaginary); |
| |
| // Find the larger magnitude. |
| if (x < y) { |
| final double tmp = x; |
| x = y; |
| y = tmp; |
| } |
| |
| if (x == 0) { |
| // Handle zero: raises the ‘‘divide-by-zero’’ floating-point exception. |
| return constructor.create(Double.NEGATIVE_INFINITY, |
| negative(real) ? Math.copySign(Math.PI, imaginary) : imaginary); |
| } |
| |
| double re; |
| |
| if (x > HALF && x < ROOT2) { |
| // x^2+y^2 close to 1. Use log1p(x^2+y^2 - 1) / 2. |
| re = Math.log1p(x2y2m1(x, y)) * logOfeOver2; |
| } else if (y == 0) { |
| // Handle real only number |
| re = log.apply(x); |
| } else if (x > SAFE_MAX || x < SAFE_MIN || y < SAFE_MIN) { |
| // Over/underflow of sqrt(x^2+y^2) |
| if (isPosInfinite(x)) { |
| // Handle infinity |
| re = x; |
| } else { |
| // Do scaling |
| final int expx = Math.getExponent(x); |
| final int expy = Math.getExponent(y); |
| if (2 * (expx - expy) > PRECISION_1) { |
| // y can be ignored |
| re = log.apply(x); |
| } else { |
| // Hull et al: |
| // "It is important that the scaling be chosen so |
| // that there is no possibility of cancellation in this addition" |
| // i.e. sx^2 + sy^2 should not be close to 1. |
| // Their paper uses expx + 2 for underflow but expx for overflow. |
| // It has been modified here to use expx - 2. |
| int scale; |
| if (x > SAFE_MAX) { |
| // overflow |
| scale = expx - 2; |
| } else { |
| // underflow |
| scale = expx + 2; |
| } |
| final double sx = Math.scalb(x, -scale); |
| final double sy = Math.scalb(y, -scale); |
| re = scale * logOf2 + 0.5 * log.apply(sx * sx + sy * sy); |
| } |
| } |
| } else { |
| // Safe region that avoids under/overflow |
| re = 0.5 * log.apply(x * x + y * y); |
| } |
| |
| // All ISO C99 edge cases for the imaginary are satisfied by the Math library. |
| return constructor.create(re, arg()); |
| } |
| |
| /** |
| * Compute {@code x^2 + y^2 - 1} in high precision. |
| * Assumes that the values x and y can be multiplied without overflow; that |
| * {@code x >= y}; and both values are positive. |
| * |
| * @param x the x value |
| * @param y the y value |
| * @return {@code x^2 + y^2 - 1}. |
| */ |
| private static double x2y2m1(double x, double y) { |
| // Hull et al used (x-1)*(x+1)+y*y. |
| // From the paper on page 236: |
| |
| // If x == 1 there is no cancellation. |
| |
| // If x > 1, there is also no cancellation, but the argument is now accurate |
| // only to within a factor of 1 + 3 EPSILSON (note that x – 1 is exact), |
| // so that error = 3 EPSILON. |
| |
| // If x < 1, there can be serious cancellation: |
| |
| // If 4 y^2 < |x^2 – 1| the cancellation is not serious ... the argument is accurate |
| // only to within a factor of 1 + 4 EPSILSON so that error = 4 EPSILON. |
| |
| // Otherwise there can be serious cancellation and the relative error in the real part |
| // could be enormous. |
| |
| // TODO - investigate the computation in high precision using |
| // LinearCombination#value(double, double, double, double, double, double) |
| // from o.a.c.numbers.arrays. |
| final double xm1xp1 = (x - 1) * (x + 1); |
| final double yy = y * y; |
| if (x < 1 && 4 * yy > Math.abs(xm1xp1)) { |
| // Large relative error... |
| return xm1xp1 + yy; |
| } |
| return xm1xp1 + yy; |
| } |
| |
| /** |
| * Returns the complex power of this complex number raised to the power of \( x \). |
| * Implements the formula: |
| * |
| * <p>\[ z^x = e^{x \ln(z)} \] |
| * |
| * <p>If this complex number is zero then this method returns zero if \( x \) is positive |
| * in the real component and zero in the imaginary component; |
| * otherwise it returns NaN + iNaN. |
| * |
| * @param x The exponent to which this complex number is to be raised. |
| * @return <code>this<sup>x</sup></code>. |
| * @see #log() |
| * @see #multiply(Complex) |
| * @see #exp() |
| * @see <a href="http://mathworld.wolfram.com/ComplexExponentiation.html">Complex exponentiation</a> |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/Power/">Power</a> |
| */ |
| public Complex pow(Complex x) { |
| if (real == 0 && |
| imaginary == 0) { |
| // This value is zero. Test the other. |
| if (x.real > 0 && |
| x.imaginary == 0) { |
| // 0 raised to positive number is 0 |
| return ZERO; |
| } |
| // 0 raised to anything else is NaN |
| return NAN; |
| } |
| return log().multiply(x).exp(); |
| } |
| |
| /** |
| * Returns the complex power of this complex number raised to the power of \( x \). |
| * Implements the formula: |
| * |
| * <p>\[ z^x = e^{x \ln(z)} \] |
| * |
| * <p>If this complex number is zero then this method returns zero if \( x \) is positive; |
| * otherwise it returns NaN + iNaN. |
| * |
| * @param x The exponent to which this complex number is to be raised. |
| * @return <code>this<sup>x</sup></code>. |
| * @see #log() |
| * @see #multiply(double) |
| * @see #exp() |
| * @see #pow(Complex) |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/Power/">Power</a> |
| */ |
| public Complex pow(double x) { |
| if (real == 0 && |
| imaginary == 0) { |
| // This value is zero. Test the other. |
| if (x > 0) { |
| // 0 raised to positive number is 0 |
| return ZERO; |
| } |
| // 0 raised to anything else is NaN |
| return NAN; |
| } |
| return log().multiply(x).exp(); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/Sine.html"> |
| * sine</a> of this complex number. |
| * |
| * <p>\[ \sin(z) = \frac{1}{2} i \left( e^{-iz} - e^{iz} \right) \] |
| * |
| * <p>This is an odd function: \( \sin(z) = -\sin(-z) \). |
| * |
| * <p>This is implemented using real \( x \) and imaginary \( y \) parts: |
| * |
| * <p>\[ \sin(x + iy) = \sin(x)\cosh(y) + i \cos(x)\sinh(y) \] |
| * |
| * <p>As per the C99 standard this function is computed using the trigonomic identity: |
| * |
| * <p>\[ \sin(z) = -i \sinh(iz) \] |
| * |
| * @return The sine of this complex number. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/Sin/">Sin</a> |
| */ |
| public Complex sin() { |
| // Define in terms of sinh |
| // sin(z) = -i sinh(iz) |
| // Multiply this number by I, compute sinh, then multiply by back |
| return sinh(-imaginary, real, Complex::multiplyNegativeI); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/HyperbolicSine.html"> |
| * hyperbolic sine</a> of this complex number. |
| * |
| * <p>\[ \sinh(z) = \frac{1}{2} \left( e^{z} - e^{-z} \right) \] |
| * |
| * <p>The hyperbolic sine of \( z \) is an entire function in the complex plane. |
| * and is periodic with respect to the imaginary component with period \( 2\pi i \). |
| * |
| * <ul> |
| * <li>{@code z.conj().sinh() == z.sinh().conj()}. |
| * <li>This is an odd function: \( \sinh(z) = -\sinh(-z) \). |
| * <li>If {@code z} is +0 + i0, returns +0 + i0. |
| * <li>If {@code z} is +0 + i∞, returns ±0 + iNaN (where the sign of the real part of the result is unspecified). |
| * <li>If {@code z} is +0 + iNaN, returns ±0 + iNaN (where the sign of the real part of the result is unspecified). |
| * <li>If {@code z} is x + i∞ for positive finite x, returns NaN + iNaN. |
| * <li>If {@code z} is x + iNaN for finite nonzero x, returns NaN + iNaN. |
| * <li>If {@code z} is +∞ + i0, returns +∞ + i0. |
| * <li>If {@code z} is +∞ + iy for positive finite y, returns +∞ cis(y) (see {@link #ofCis(double)}. |
| * <li>If {@code z} is +∞ + i∞, returns ±∞ + iNaN (where the sign of the real part of the result is unspecified). |
| * <li>If {@code z} is +∞ + iNaN, returns ±∞ + iNaN (where the sign of the real part of the result is unspecified). |
| * <li>If {@code z} is NaN + i0, returns NaN + i0. |
| * <li>If {@code z} is NaN + iy for all nonzero numbers y, returns NaN + iNaN. |
| * <li>If {@code z} is NaN + iNaN, returns NaN + iNaN. |
| * </ul> |
| * |
| * <p>This is implemented using real \( x \) and imaginary \( y \) parts: |
| * |
| * <p>\[ \sinh(x + iy) = \sinh(x)\cos(y) + i \cosh(x)\sin(y) \] |
| * |
| * @return The hyperbolic sine of this complex number. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/Sinh/">Sinh</a> |
| */ |
| public Complex sinh() { |
| return sinh(real, imaginary, Complex::ofCartesian); |
| } |
| |
| /** |
| * Returns the hyperbolic sine of the complex number. |
| * |
| * <p>This function exists to allow implementation of the identity |
| * {@code sin(z) = -i sinh(iz)}.<p> |
| * |
| * @param real Real part. |
| * @param imaginary Imaginary part. |
| * @param constructor Constructor. |
| * @return The hyperbolic sine of the complex number. |
| */ |
| private static Complex sinh(double real, double imaginary, ComplexConstructor constructor) { |
| if ((Double.isInfinite(real) && !Double.isFinite(imaginary)) || |
| (real == 0 && !Double.isFinite(imaginary))) { |
| return constructor.create(real, Double.NaN); |
| } |
| if (imaginary == 0 && !Double.isFinite(real)) { |
| return constructor.create(real, imaginary); |
| } |
| return constructor.create(Math.sinh(real) * Math.cos(imaginary), |
| Math.cosh(real) * Math.sin(imaginary)); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/SquareRoot.html"> |
| * square root</a> of this complex number. |
| * |
| * <p>\[ \sqrt{x + iy} = \frac{1}{2} \sqrt{2} \left( \sqrt{ \sqrt{x^2 + y^2} + x } + i\ \text{sgn}(y) \sqrt{ \sqrt{x^2 + y^2} - x } \right) \] |
| * |
| * <p>The square root of \( z \) is in the range \( [0, +\infty) \) along the real axis and |
| * is unbounded along the imaginary axis. Special cases: |
| * |
| * <ul> |
| * <li>{@code z.conj().sqrt() == z.sqrt().conj()}. |
| * <li>If {@code z} is ±0 + i0, returns +0 + i0. |
| * <li>If {@code z} is x + i∞ for all x (including NaN), returns +∞ + i∞. |
| * <li>If {@code z} is x + iNaN for finite x, returns NaN + iNaN. |
| * <li>If {@code z} is −∞ + iy for finite positive-signed y, returns +0 + i∞. |
| * <li>If {@code z} is +∞ + iy for finite positive-signed y, returns +∞ + i0. |
| * <li>If {@code z} is −∞ + iNaN, returns NaN ± i∞ (where the sign of the imaginary part of the result is unspecified). |
| * <li>If {@code z} is +∞ + iNaN, returns +∞ + iNaN. |
| * <li>If {@code z} is NaN + iy for finite y, returns NaN + iNaN. |
| * <li>If {@code z} is NaN + iNaN, returns NaN + iNaN. |
| * </ul> |
| * |
| * <p>Implements the following algorithm to compute \( \sqrt{x + iy} \): |
| * <ol> |
| * <li>Let \( t = \sqrt{2 (|x| + |x + iy|)} \) |
| * <li>if \( x \geq 0 \) return \( \frac{t}{2} + i \frac{y}{t} \) |
| * <li>else return \( \frac{|y|}{t} + i\ \text{sgn}(y) \frac{t}{2} \) |
| * </ol> |
| * where: |
| * <ul> |
| * <li>\( |x| =\ \){@link Math#abs(double) abs}(x) |
| * <li>\( |x + y i| =\ \){@link Complex#abs} |
| * <li>\( \text{sgn}(y) =\ \){@link Math#copySign(double,double) copySign}(1.0, y) |
| * </ul> |
| * |
| * <p>The implementation is overflow and underflow safe based on the method described in:</p> |
| * <blockquote> |
| * T E Hull, Thomas F Fairgrieve and Ping Tak Peter Tang (1994) |
| * Implementing complex elementary functions using exception handling. |
| * ACM Transactions on Mathematical Software, Vol 20, No 2, pp 215-244. |
| * </blockquote> |
| * |
| * @return The square root of this complex number. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/Sqrt/">Sqrt</a> |
| */ |
| public Complex sqrt() { |
| return sqrt(real, imaginary); |
| } |
| |
| /** |
| * Returns the square root of the complex number {@code sqrt(x + i y)}. |
| * |
| * @param real Real component. |
| * @param imaginary Imaginary component. |
| * @return The square root of the complex number. |
| */ |
| private static Complex sqrt(double real, double imaginary) { |
| // Handle NaN |
| if (Double.isNaN(real) || Double.isNaN(imaginary)) { |
| // Check for infinite |
| if (Double.isInfinite(imaginary)) { |
| return new Complex(Double.POSITIVE_INFINITY, imaginary); |
| } |
| if (Double.isInfinite(real)) { |
| if (real == Double.NEGATIVE_INFINITY) { |
| return new Complex(Double.NaN, Math.copySign(Double.POSITIVE_INFINITY, imaginary)); |
| } |
| return new Complex(Double.POSITIVE_INFINITY, Double.NaN); |
| } |
| return NAN; |
| } |
| |
| // Compute with positive values and determine sign at the end |
| final double x = Math.abs(real); |
| final double y = Math.abs(imaginary); |
| |
| // Compute |
| double t; |
| |
| if (inRegion(x, y, SAFE_MIN, SAFE_MAX)) { |
| // No over/underflow of x^2 + y^2 |
| t = Math.sqrt(2 * (Math.sqrt(x * x + y * y) + x)); |
| } else { |
| // Potential over/underflow. First check infinites and real/imaginary only. |
| |
| // Check for infinite |
| if (isPosInfinite(y)) { |
| return new Complex(Double.POSITIVE_INFINITY, imaginary); |
| } else if (isPosInfinite(x)) { |
| if (real == Double.NEGATIVE_INFINITY) { |
| return new Complex(0, Math.copySign(Double.POSITIVE_INFINITY, imaginary)); |
| } |
| return new Complex(Double.POSITIVE_INFINITY, Math.copySign(0, imaginary)); |
| } else if (y == 0) { |
| // Real only |
| final double sqrtAbs = Math.sqrt(x); |
| if (real < 0) { |
| return new Complex(0, Math.copySign(sqrtAbs, imaginary)); |
| } |
| return new Complex(sqrtAbs, imaginary); |
| } else if (x == 0) { |
| // Imaginary only |
| final double sqrtAbs = Math.sqrt(y) / ROOT2; |
| return new Complex(sqrtAbs, Math.copySign(sqrtAbs, imaginary)); |
| } else { |
| // Over/underflow |
| // scale so that abs(x) is near 1, with even exponent. |
| final int scale = getMaxExponent(x, y) & MASK_INT_TO_EVEN; |
| final double sx = Math.scalb(x, -scale); |
| final double sy = Math.scalb(y, -scale); |
| final double st = Math.sqrt(2 * (Math.sqrt(sx * sx + sy * sy) + sx)); |
| // Rescale. This works if exponent is even: |
| // st * sqrt(2^scale) = st * (2^scale)^0.5 = st * 2^(scale*0.5) |
| t = Math.scalb(st, scale / 2); |
| } |
| } |
| |
| if (real >= 0) { |
| return new Complex(t / 2, imaginary / t); |
| } |
| return new Complex(y / t, Math.copySign(t / 2, imaginary)); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/Tangent.html"> |
| * tangent</a> of this complex number. |
| * |
| * <p>\[ \tan(z) = \frac{i(e^{-iz} - e^{iz})}{e^{-iz} + e^{iz}} \] |
| * |
| * <p>This is an odd function: \( \tan(z) = -\tan(-z) \). |
| * |
| * <p>This is implemented using real \( x \) and imaginary \( y \) parts:</p> |
| * \[ \tan(x + iy) = \frac{\sin(2x)}{\cos(2x)+\cosh(2y)} + i \frac{\sinh(2y)}{\cos(2x)+\cosh(2y)} \] |
| * |
| * <p>As per the C99 standard this function is computed using the trigonomic identity:</p> |
| * \[ \tan(z) = -i \tanh(iz) \] |
| * |
| * @return The tangent of this complex number. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/Tan/">Tangent</a> |
| */ |
| public Complex tan() { |
| // Define in terms of tanh |
| // tan(z) = -i tanh(iz) |
| // Multiply this number by I, compute tanh, then multiply by back |
| return tanh(-imaginary, real, Complex::multiplyNegativeI); |
| } |
| |
| /** |
| * Returns the |
| * <a href="http://mathworld.wolfram.com/HyperbolicTangent.html"> |
| * hyperbolic tangent</a> of this complex number. |
| * |
| * <p>\[ \tanh(z) = \frac{e^z - e^{-z}}{e^z + e^{-z}} \] |
| * |
| * <p>The hyperbolic tangent of \( z \) is an entire function in the complex plane. |
| * and is periodic with respect to the imaginary component with period \( \pi i \) |
| * and has poles of the first order along the imaginary line, at coordinates |
| * \( (0, \pi(\frac{1}{2} + n)) \). |
| * Note that the {@code double} floating-point representation is unable to exactly represent |
| * \( \pi/2 \) and there is no value for which a pole error occurs. |
| * |
| * <ul> |
| * <li>{@code z.conj().tanh() == z.tanh().conj()}. |
| * <li>This is an odd function: \( \tanh(z) = -\tanh(-z) \). |
| * <li>If {@code z} is +0 + i0, returns +0 + i0. |
| * <li>If {@code z} is x + i∞ for finite x, returns NaN + iNaN. |
| * <li>If {@code z} is x + iNaN for finite x, returns NaN + iNaN. |
| * <li>If {@code z} is +∞ + iy for positive-signed finite y, returns 1 + i0 sin(2y). |
| * <li>If {@code z} is +∞ + i∞, returns 1 ± i0 (where the sign of the imaginary part of the result is unspecified). |
| * <li>If {@code z} is +∞ + iNaN, returns 1 ± i0 (where the sign of the imaginary part of the result is unspecified). |
| * <li>If {@code z} is NaN + i0, returns NaN + i0. |
| * <li>If {@code z} is NaN + iy for all nonzero numbers y, returns NaN + iNaN. |
| * <li>If {@code z} is NaN + iNaN, returns NaN + iNaN. |
| * </ul> |
| * |
| * <p>This is implemented using real \( x \) and imaginary \( y \) parts: |
| * |
| * <p>\[ \tan(x + iy) = \frac{\sinh(2x)}{\cosh(2x)+\cos(2y)} + i \frac{\sin(2y)}{\cosh(2x)+\cos(2y)} \] |
| * |
| * @return The hyperbolic tangent of this complex number. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/Tanh/">Tanh</a> |
| */ |
| public Complex tanh() { |
| return tanh(real, imaginary, Complex::ofCartesian); |
| } |
| |
| /** |
| * Returns the hyperbolic tangent of this complex number. |
| * |
| * <p>This function exists to allow implementation of the identity |
| * {@code tan(z) = -i tanh(iz)}.<p> |
| * |
| * @param real Real part. |
| * @param imaginary Imaginary part. |
| * @param constructor Constructor. |
| * @return The hyperbolic tangent of the complex number. |
| */ |
| private static Complex tanh(double real, double imaginary, ComplexConstructor constructor) { |
| if (Double.isInfinite(real)) { |
| if (Double.isFinite(imaginary)) { |
| return constructor.create(Math.copySign(1, real), Math.copySign(0, sin2(imaginary))); |
| } |
| // imaginary is infinite or NaN |
| return constructor.create(Math.copySign(1, real), Math.copySign(0, imaginary)); |
| } |
| |
| if (real == 0) { |
| if (Double.isFinite(imaginary)) { |
| // Identity: sin x / (1 + cos x) = tan(x/2) |
| return constructor.create(real, Math.tan(imaginary)); |
| } |
| return constructor.create(Double.NaN, Double.NaN); |
| } |
| if (imaginary == 0) { |
| if (Double.isNaN(real)) { |
| return constructor.create(Double.NaN, imaginary); |
| } |
| // Identity: sinh x / (1 + cosh x) = tanh(x/2) |
| return constructor.create(Math.tanh(real), imaginary); |
| } |
| |
| final double real2 = 2 * real; |
| |
| // Math.cosh returns positive infinity for infinity. |
| // cosh -> inf |
| final double divisor = Math.cosh(real2) + cos2(imaginary); |
| |
| // Math.sinh returns the input infinity for infinity. |
| // sinh -> inf for positive x; else -inf |
| final double sinhRe2 = Math.sinh(real2); |
| |
| // Avoid inf / inf |
| if (Double.isInfinite(sinhRe2) && Double.isInfinite(divisor)) { |
| // Handle as if real was infinite |
| return constructor.create(Math.copySign(1, real), Math.copySign(0, imaginary)); |
| } |
| return constructor.create(sinhRe2 / divisor, |
| sin2(imaginary) / divisor); |
| } |
| |
| /** |
| * Safely compute {@code cos(2*a)} when {@code a} is finite. |
| * Note that {@link Math#cos(double)} returns NaN when the input is infinite. |
| * If {@code 2*a} is finite use {@code Math.cos(2*a)}; otherwise use the identity: |
| * <pre> |
| * <code> |
| * cos(2a) = 2 cos<sup>2</sup>(a) - 1 |
| * </code> |
| * </pre> |
| * |
| * @param a Angle a. |
| * @return The cosine of 2a. |
| * @see Math#cos(double) |
| */ |
| private static double cos2(double a) { |
| final double twoA = 2 * a; |
| if (Double.isFinite(twoA)) { |
| return Math.cos(twoA); |
| } |
| final double cosA = Math.cos(a); |
| return 2 * cosA * cosA - 1; |
| } |
| |
| /** |
| * Safely compute {@code sin(2*a)} when {@code a} is finite. |
| * Note that {@link Math#sin(double)} returns NaN when the input is infinite. |
| * If {@code 2*a} is finite use {@code Math.sin(2*a)}; otherwise use the identity: |
| * <pre> |
| * <code> |
| * sin(2a) = 2 sin(a) cos(a) |
| * </code> |
| * </pre> |
| * |
| * @param a Angle a. |
| * @return The sine of 2a. |
| * @see Math#sin(double) |
| */ |
| private static double sin2(double a) { |
| final double twoA = 2 * a; |
| if (Double.isFinite(twoA)) { |
| return Math.sin(twoA); |
| } |
| return 2 * Math.sin(a) * Math.cos(a); |
| } |
| |
| /** |
| * Returns the argument of this complex number. |
| * |
| * <p>The argument is the angle phi between the positive real axis and |
| * the point representing this number in the complex plane. |
| * The value returned is between \( -\pi \) (not inclusive) |
| * and \( \pi \) (inclusive), with negative values returned for numbers with |
| * negative imaginary parts. |
| * |
| * <p>If either real or imaginary part (or both) is NaN, NaN is returned. |
| * Infinite parts are handled as {@linkplain Math#atan2} handles them, |
| * essentially treating finite parts as zero in the presence of an |
| * infinite coordinate and returning a multiple of \( \frac{\pi}{4} \) depending on |
| * the signs of the infinite parts. |
| * |
| * <p>This code follows the |
| * <a href="http://www.iso-9899.info/wiki/The_Standard">ISO C Standard</a>, Annex G, |
| * in calculating the returned value using the {@code atan2(y, x)} method for complex |
| * \( x + iy \). |
| * |
| * @return The argument of this complex number. |
| * @see Math#atan2(double, double) |
| */ |
| public double arg() { |
| // Delegate |
| return Math.atan2(imaginary, real); |
| } |
| |
| /** |
| * Returns the n-th roots of this complex number. |
| * The nth roots are defined by the formula: |
| * |
| * <p>\[ z_k = |z|^{\frac{1}{n}} \left( \cos \left(\phi + \frac{2\pi k}{n} \right) + i \sin \left(\phi + \frac{2\pi k}{n} \right) \right) \] |
| * |
| * <p>for \( k=0, 1, \ldots, n-1 \), where \( |z| \) and \( \phi \) |
| * are respectively the {@link #abs() modulus} and |
| * {@link #arg() argument} of this complex number. |
| * |
| * <p>If one or both parts of this complex number is NaN, a list with all |
| * all elements set to {@code NaN + i NaN} is returned.</p> |
| * |
| * @param n Degree of root. |
| * @return A list of all {@code n}-th roots of this complex number. |
| * @throws IllegalArgumentException if {@code n} is zero. |
| * @see <a href="http://functions.wolfram.com/ElementaryFunctions/Root/">Root</a> |
| */ |
| public List<Complex> nthRoot(int n) { |
| if (n == 0) { |
| throw new IllegalArgumentException("cannot compute zeroth root"); |
| } |
| |
| final List<Complex> result = new ArrayList<>(); |
| |
| // nth root of abs -- faster / more accurate to use a solver here? |
| final double nthRootOfAbs = Math.pow(abs(), 1.0 / n); |
| |
| // Compute nth roots of complex number with k = 0, 1, ... n-1 |
| final double nthPhi = arg() / n; |
| final double slice = 2 * Math.PI / n; |
| double innerPart = nthPhi; |
| for (int k = 0; k < Math.abs(n); k++) { |
| // inner part |
| final double realPart = nthRootOfAbs * Math.cos(innerPart); |
| final double imaginaryPart = nthRootOfAbs * Math.sin(innerPart); |
| result.add(new Complex(realPart, imaginaryPart)); |
| innerPart += slice; |
| } |
| |
| return result; |
| } |
| |
| /** |
| * Returns a string representation of the complex number. |
| * |
| * <p>The string will represent the numeric values of the real and imaginary parts. |
| * The values are split by a separator and surrounded by parentheses. |
| * The string can be {@link #parse(String) parsed} to obtain an instance with the same value. |
| * |
| * <p>The format for complex number \( x + i y \) is {@code "(x,y)"}, with \( x \) and |
| * \( y \) converted as if using {@link Double#toString(double)}. |
| * |
| * @return A string representation of the complex number. |
| * @see #parse(String) |
| * @see Double#toString(double) |
| */ |
| @Override |
| public String toString() { |
| return new StringBuilder(TO_STRING_SIZE) |
| .append(FORMAT_START) |
| .append(real).append(FORMAT_SEP) |
| .append(imaginary) |
| .append(FORMAT_END) |
| .toString(); |
| } |
| |
| /** |
| * Returns {@code true} if the values are equal according to semantics of |
| * {@link Double#equals(Object)}. |
| * |
| * @param x Value |
| * @param y Value |
| * @return {@code Double.valueof(x).equals(Double.valueOf(y))}. |
| */ |
| private static boolean equals(double x, double y) { |
| return Double.doubleToLongBits(x) == Double.doubleToLongBits(y); |
| } |
| |
| /** |
| * Check that a value is negative. It must meet all the following conditions: |
| * <ul> |
| * <li>it is not {@code NaN},</li> |
| * <li>it is negative signed,</li> |
| * </ul> |
| * |
| * <p>Note: This is true for negative zero.</p> |
| * |
| * @param d Value. |
| * @return {@code true} if {@code d} is negative. |
| */ |
| private static boolean negative(double d) { |
| return d < 0 || Double.doubleToLongBits(d) == NEGATIVE_ZERO_LONG_BITS; |
| } |
| |
| /** |
| * Check that a value is positive infinity. Used to replace {@link Double#isInfinite()} |
| * when the input value is known to be positive (i.e. in the case where it have been |
| * set using {@link Math#abs(double)}). |
| * |
| * @param d Value. |
| * @return {@code true} if {@code d} is +inf. |
| */ |
| private static boolean isPosInfinite(double d) { |
| return d == Double.POSITIVE_INFINITY; |
| } |
| |
| /** |
| * Create a complex number given the real and imaginary parts, then multiply by {@code -i}. |
| * This is used in functions that implement trigonomic identities. It is the functional |
| * equivalent of: |
| * |
| * <pre> |
| * z = new Complex(real, imaginary).multiplyImaginary(-1); |
| * </pre> |
| * |
| * @param real Real part. |
| * @param imaginary Imaginary part. |
| * @return {@code Complex} object. |
| */ |
| private static Complex multiplyNegativeI(double real, double imaginary) { |
| return new Complex(imaginary, -real); |
| } |
| |
| /** |
| * Change the sign of the magnitude based on the signed value. |
| * |
| * <p>If the signed value is negative then the result is {@code -magnitude}; otherwise |
| * return {@code magnitude}. |
| * |
| * <p>A signed value of {@code -0.0} is treated as negative. A signed value of {@code NaN} |
| * is treated as positive. |
| * |
| * <p>This is not the same as {@link Math#copySign(double, double)} as this method |
| * will change the sign based on the signed value rather than copy the sign. |
| * |
| * @param magnitude the magnitude |
| * @param signedValue the signed value |
| * @return magnitude or -magnitude. |
| * @see #negative(double) |
| */ |
| private static double changeSign(double magnitude, double signedValue) { |
| return negative(signedValue) ? -magnitude : magnitude; |
| } |
| |
| /** |
| * Returns the largest unbiased exponent used in the representation of the |
| * two numbers. Special cases: |
| * |
| * <ul> |
| * <li>If either argument is NaN or infinite, then the result is |
| * {@link Double#MAX_EXPONENT} + 1. |
| * <li>If both arguments are zero or subnormal, then the result is |
| * {@link Double#MIN_EXPONENT} -1. |
| * </ul> |
| * |
| * @param a the first value |
| * @param b the second value |
| * @return The maximum unbiased exponent of the values. |
| * @see Math#getExponent(double) |
| */ |
| private static int getMaxExponent(double a, double b) { |
| // This could return: |
| // Math.getExponent(Math.max(Math.abs(a), Math.abs(b))) |
| // A speed test is required to determine performance. |
| |
| return Math.max(Math.getExponent(a), Math.getExponent(b)); |
| } |
| |
| /** |
| * Checks if both x and y are in the region defined by the minimum and maximum. |
| * |
| * @param x x value. |
| * @param y y value. |
| * @param min the minimum (exclusive). |
| * @param max the maximum (exclusive). |
| * @return true if inside the region. |
| */ |
| private static boolean inRegion(double x, double y, double min, double max) { |
| return (x < max) && (x > min) && (y < max) && (y > min); |
| } |
| |
| /** |
| * Creates an exception. |
| * |
| * @param message Message prefix. |
| * @param error Input that caused the error. |
| * @param cause Underlying exception (if any). |
| * @return A new instance. |
| */ |
| private static NumberFormatException parsingException(String message, |
| Object error, |
| Throwable cause) { |
| // Not called with a null message or error |
| final StringBuilder sb = new StringBuilder(100) |
| .append(message) |
| .append(" '").append(error).append('\''); |
| if (cause != null) { |
| sb.append(": ").append(cause.getMessage()); |
| } |
| |
| return new NumberFormatException(sb.toString()); |
| } |
| } |
