CHANGELOG.md

@@ -8,6 +8,7 @@
 - Automatic README generation for features (#139)
 - Native support for `memory`, `core` and `dimensions`
 - `kmath-ejml` to supply EJML SimpleMatrix wrapper.
+- Basic Quaternion vector support.
 
 ### Changed
 - Package changed from `scientifik` to `kscience.kmath`.

kmath-core/src/commonMain/kotlin/kscience/kmath/operations/Complex.kt

@@ -42,22 +42,21 @@ private val PI_DIV_2 = Complex(PI / 2, 0)
  * A field of [Complex].
  */
 public object ComplexField : ExtendedField<Complex>, Norm<Complex, Complex> {
-    override val zero: Complex = 0.0.toComplex()
+    override val zero: Complex by lazy { 0.toComplex() }
-    override val one: Complex = 1.0.toComplex()
+    override val one: Complex by lazy { 1.toComplex() }
 
     /**
      * The imaginary unit.
      */
-    public val i: Complex = Complex(0.0, 1.0)
+    public val i: Complex by lazy { Complex(0, 1) }
 
-    override fun add(a: Complex, b: Complex): Complex = Complex(a.re + b.re, a.im + b.im)
+    public override fun add(a: Complex, b: Complex): Complex = Complex(a.re + b.re, a.im + b.im)
+    public override fun multiply(a: Complex, k: Number): Complex = Complex(a.re * k.toDouble(), a.im * k.toDouble())
 
-    override fun multiply(a: Complex, k: Number): Complex = Complex(a.re * k.toDouble(), a.im * k.toDouble())
+    public override fun multiply(a: Complex, b: Complex): Complex =
-
-    override fun multiply(a: Complex, b: Complex): Complex =
         Complex(a.re * b.re - a.im * b.im, a.re * b.im + a.im * b.re)
 
-    override fun divide(a: Complex, b: Complex): Complex = when {
+    public override fun divide(a: Complex, b: Complex): Complex = when {
         b.re.isNaN() || b.im.isNaN() -> Complex(Double.NaN, Double.NaN)
 
         (if (b.im < 0) -b.im else +b.im) < (if (b.re < 0) -b.re else +b.re) -> {
@@ -83,31 +82,31 @@ public object ComplexField : ExtendedField<Complex>, Norm<Complex, Complex> {
         }
     }
 
-    override fun sin(arg: Complex): Complex = i * (exp(-i * arg) - exp(i * arg)) / 2
+    public override fun sin(arg: Complex): Complex = i * (exp(-i * arg) - exp(i * arg)) / 2
-    override fun cos(arg: Complex): Complex = (exp(-i * arg) + exp(i * arg)) / 2
+    public override fun cos(arg: Complex): Complex = (exp(-i * arg) + exp(i * arg)) / 2
 
-    override fun tan(arg: Complex): Complex {
+    public override fun tan(arg: Complex): Complex {
         val e1 = exp(-i * arg)
         val e2 = exp(i * arg)
         return i * (e1 - e2) / (e1 + e2)
     }
 
-    override fun asin(arg: Complex): Complex = -i * ln(sqrt(1 - (arg * arg)) + i * arg)
+    public override fun asin(arg: Complex): Complex = -i * ln(sqrt(1 - (arg * arg)) + i * arg)
-    override fun acos(arg: Complex): Complex = PI_DIV_2 + i * ln(sqrt(1 - (arg * arg)) + i * arg)
+    public override fun acos(arg: Complex): Complex = PI_DIV_2 + i * ln(sqrt(1 - (arg * arg)) + i * arg)
 
-    override fun atan(arg: Complex): Complex {
+    public override fun atan(arg: Complex): Complex {
         val iArg = i * arg
         return i * (ln(1 - iArg) - ln(1 + iArg)) / 2
     }
 
-    override fun power(arg: Complex, pow: Number): Complex = if (arg.im == 0.0)
+    public override fun power(arg: Complex, pow: Number): Complex = if (arg.im == 0.0)
         arg.re.pow(pow.toDouble()).toComplex()
     else
         exp(pow * ln(arg))
 
-    override fun exp(arg: Complex): Complex = exp(arg.re) * (cos(arg.im) + i * sin(arg.im))
+    public override fun exp(arg: Complex): Complex = exp(arg.re) * (cos(arg.im) + i * sin(arg.im))
 
-    override fun ln(arg: Complex): Complex = ln(arg.r) + i * atan2(arg.im, arg.re)
+    public override fun ln(arg: Complex): Complex = ln(arg.r) + i * atan2(arg.im, arg.re)
 
     /**
      * Adds complex number to real one.
@@ -116,7 +115,7 @@ public object ComplexField : ExtendedField<Complex>, Norm<Complex, Complex> {
      * @param c the augend.
      * @return the sum.
      */
-    public operator fun Double.plus(c: Complex): Complex = add(this.toComplex(), c)
+    public operator fun Double.plus(c: Complex): Complex = add(toComplex(), c)
 
     /**
      * Subtracts complex number from real one.
@@ -125,7 +124,7 @@ public object ComplexField : ExtendedField<Complex>, Norm<Complex, Complex> {
      * @param c the subtrahend.
      * @return the difference.
      */
-    public operator fun Double.minus(c: Complex): Complex = add(this.toComplex(), -c)
+    public operator fun Double.minus(c: Complex): Complex = add(toComplex(), -c)
 
     /**
      * Adds real number to complex one.
@@ -154,9 +153,9 @@ public object ComplexField : ExtendedField<Complex>, Norm<Complex, Complex> {
      */
     public operator fun Double.times(c: Complex): Complex = Complex(c.re * this, c.im * this)
 
-    override fun norm(arg: Complex): Complex = sqrt(arg.conjugate * arg)
+    public override fun Complex.unaryMinus(): Complex = Complex(-re, -im)
-
+    public override fun norm(arg: Complex): Complex = sqrt(arg.conjugate * arg)
-    override fun symbol(value: String): Complex = if (value == "i") i else super.symbol(value)
+    public override fun symbol(value: String): Complex = if (value == "i") i else super.symbol(value)
 }
 
 /**
@@ -169,26 +168,23 @@ public data class Complex(val re: Double, val im: Double) : FieldElement<Complex
     Comparable<Complex> {
     public constructor(re: Number, im: Number) : this(re.toDouble(), im.toDouble())
 
-    override val context: ComplexField get() = ComplexField
+    public override val context: ComplexField
-
+        get() = ComplexField
-    override fun unwrap(): Complex = this
-
-    override fun Complex.wrap(): Complex = this
-
-    override fun compareTo(other: Complex): Int = r.compareTo(other.r)
-
-    override fun toString(): String {
-        return "($re + i*$im)"
-    }
 
+    public override fun unwrap(): Complex = this
+    public override fun Complex.wrap(): Complex = this
+    public override fun compareTo(other: Complex): Int = r.compareTo(other.r)
+    public override fun toString(): String = "($re + $im * i)"
+    public override fun minus(b: Complex): Complex = Complex(re - b.re, im - b.im)
 
     public companion object : MemorySpec<Complex> {
-        override val objectSize: Int
+        public override val objectSize: Int
             get() = 16
 
-        override fun MemoryReader.read(offset: Int): Complex = Complex(readDouble(offset), readDouble(offset + 8))
+        public override fun MemoryReader.read(offset: Int): Complex =
+            Complex(readDouble(offset), readDouble(offset + 8))
 
-        override fun MemoryWriter.write(offset: Int, value: Complex) {
+        public override fun MemoryWriter.write(offset: Int, value: Complex) {
             writeDouble(offset, value.re)
             writeDouble(offset + 8, value.im)
         }
@@ -201,7 +197,7 @@ public data class Complex(val re: Double, val im: Double) : FieldElement<Complex
  * @receiver the real part.
  * @return the new complex number.
  */
-public fun Number.toComplex(): Complex = Complex(this, 0.0)
+public fun Number.toComplex(): Complex = Complex(this, 0)
 
 /**
  * Creates a new buffer of complex numbers with the specified [size], where each element is calculated by calling the

kmath-core/src/commonMain/kotlin/kscience/kmath/operations/Quaternion.kt

@@ -0,0 +1,294 @@
+package kscience.kmath.operations
+
+import kscience.kmath.memory.MemoryReader
+import kscience.kmath.memory.MemorySpec
+import kscience.kmath.memory.MemoryWriter
+import kscience.kmath.structures.Buffer
+import kscience.kmath.structures.MemoryBuffer
+import kscience.kmath.structures.MutableBuffer
+import kscience.kmath.structures.MutableMemoryBuffer
+import kotlin.math.*
+
+/**
+ * This quaternion's conjugate.
+ */
+public val Quaternion.conjugate: Quaternion
+    get() = QuaternionField { z - x * i - y * j - z * k }
+
+/**
+ * This quaternion's reciprocal.
+ */
+public val Quaternion.reciprocal: Quaternion
+    get() {
+        val n = QuaternionField { norm(this@reciprocal) }
+        return conjugate / (n * n)
+    }
+
+/**
+ * Absolute value of the quaternion.
+ */
+public val Quaternion.r: Double
+    get() = sqrt(w * w + x * x + y * y + z * z)
+
+/**
+ * A field of [Quaternion].
+ */
+public object QuaternionField : Field<Quaternion>, Norm<Quaternion, Quaternion>, PowerOperations<Quaternion>,
+    ExponentialOperations<Quaternion> {
+    override val zero: Quaternion by lazy { 0.toQuaternion() }
+    override val one: Quaternion by lazy { 1.toQuaternion() }
+
+    /**
+     * The `i` quaternion unit.
+     */
+    public val i: Quaternion by lazy { Quaternion(0, 1, 0, 0) }
+
+    /**
+     * The `j` quaternion unit.
+     */
+    public val j: Quaternion by lazy { Quaternion(0, 0, 1, 0) }
+
+    /**
+     * The `k` quaternion unit.
+     */
+    public val k: Quaternion by lazy { Quaternion(0, 0, 0, 1) }
+
+    public override fun add(a: Quaternion, b: Quaternion): Quaternion =
+        Quaternion(a.w + b.w, a.x + b.x, a.y + b.y, a.z + b.z)
+
+    public override fun multiply(a: Quaternion, k: Number): Quaternion {
+        val d = k.toDouble()
+        return Quaternion(a.w * d, a.x * d, a.y * d, a.z * d)
+    }
+
+    public override fun multiply(a: Quaternion, b: Quaternion): Quaternion = Quaternion(
+        a.w * b.w - a.x * b.x - a.y * b.y - a.z * b.z,
+        a.w * b.x + a.x * b.w + a.y * b.z - a.z * b.y,
+        a.w * b.y - a.x * b.z + a.y * b.w + a.z * b.x,
+        a.w * b.z + a.x * b.y - a.y * b.x + a.z * b.w,
+    )
+
+    override fun divide(a: Quaternion, b: Quaternion): Quaternion {
+        val s = b.w * b.w + b.x * b.x + b.y * b.y + b.z * b.z
+
+        return Quaternion(
+            (b.w * a.w + b.x * a.x + b.y * a.y + b.z * a.z) / s,
+            (b.w * a.x - b.x * a.w - b.y * a.z + b.z * a.y) / s,
+            (b.w * a.y + b.x * a.z - b.y * a.w - b.z * a.x) / s,
+            (b.w * a.z - b.x * a.y + b.y * a.x - b.z * a.w) / s,
+        )
+    }
+
+    public override fun power(arg: Quaternion, pow: Number): Quaternion {
+        if (pow is Int) return pwr(arg, pow)
+        if (floor(pow.toDouble()) == pow.toDouble()) return pwr(arg, pow.toInt())
+        return exp(pow * ln(arg))
+    }
+
+    private fun pwr(x: Quaternion, a: Int): Quaternion {
+        if (a < 0) return -(pwr(x, -a))
+        if (a == 0) return one
+        if (a == 1) return x
+        if (a == 2) return pwr2(x)
+        if (a == 3) return pwr3(x)
+        if (a == 4) return pwr4(x)
+        val x4 = pwr4(x)
+        var y = x4
+        repeat((1 until a / 4).count()) { y *= x4 }
+        if (a % 4 == 3) y *= pwr3(x)
+        if (a % 4 == 2) y *= pwr2(x)
+        if (a % 4 == 1) y *= x
+        return y
+    }
+
+    private inline fun pwr2(x: Quaternion): Quaternion {
+        val aa = 2 * x.w
+
+        return Quaternion(
+            x.w * x.w - (x.x * x.x + x.y * x.y + x.z * x.z),
+            aa * x.x,
+            aa * x.y,
+            aa * x.z
+        )
+    }
+
+    private inline fun pwr3(x: Quaternion): Quaternion {
+        val a2 = x.w * x.w
+        val n1 = x.x * x.x + x.y * x.y + x.z * x.z
+        val n2 = 3.0 * a2 - n1
+
+        return Quaternion(
+            x.w * (a2 - 3 * n1),
+            x.x * n2,
+            x.y * n2,
+            x.z * n2
+        )
+    }
+
+    private inline fun pwr4(x: Quaternion): Quaternion {
+        val a2 = x.w * x.w
+        val n1 = x.x * x.x + x.y * x.y + x.z * x.z
+        val n2 = 4 * x.w * (a2 - n1)
+
+        return Quaternion(
+            a2 * a2 - 6 * a2 * n1 + n1 * n1,
+            x.x * n2,
+            x.y * n2,
+            x.z * n2
+        )
+    }
+
+    public override fun exp(arg: Quaternion): Quaternion {
+        val un = arg.x * arg.x + arg.y * arg.y + arg.z * arg.z
+        if (un == 0.0) return exp(arg.w).toQuaternion()
+        val n1 = sqrt(un)
+        val ea = exp(arg.w)
+        val n2 = ea * sin(n1) / n1
+        return Quaternion(ea * cos(n1), n2 * arg.x, n2 * arg.y, n2 * arg.z)
+    }
+
+    public override fun ln(arg: Quaternion): Quaternion {
+        val nu2 = arg.x * arg.x + arg.y * arg.y + arg.z * arg.z
+
+        if (nu2 == 0.0)
+            return if (arg.w > 0)
+                Quaternion(ln(arg.w), 0, 0, 0)
+            else {
+                val l = ComplexField { ln(arg.w.toComplex()) }
+                Quaternion(l.re, l.im, 0, 0)
+            }
+
+        val a = arg.w
+        check(nu2 > 0)
+        val n = sqrt(a * a + nu2)
+        val th = acos(a / n) / sqrt(nu2)
+        return Quaternion(ln(n), th * arg.x, th * arg.y, th * arg.z)
+    }
+
+    /**
+     * Adds quaternion to real one.
+     *
+     * @receiver the addend.
+     * @param c the augend.
+     * @return the sum.
+     */
+    public operator fun Double.plus(c: Quaternion): Quaternion = Quaternion(this + c.w, c.x, c.y, c.z)
+
+    /**
+     * Subtracts quaternion from real one.
+     *
+     * @receiver the minuend.
+     * @param c the subtrahend.
+     * @return the difference.
+     */
+    public operator fun Double.minus(c: Quaternion): Quaternion = Quaternion(this - c.w, -c.x, -c.y, -c.z)
+
+    /**
+     * Adds real number to quaternion.
+     *
+     * @receiver the addend.
+     * @param d the augend.
+     * @return the sum.
+     */
+    public operator fun Quaternion.plus(d: Double): Quaternion = Quaternion(w + d, x, y, z)
+
+    /**
+     * Subtracts real number from quaternion.
+     *
+     * @receiver the minuend.
+     * @param d the subtrahend.
+     * @return the difference.
+     */
+    public operator fun Quaternion.minus(d: Double): Quaternion = Quaternion(w - d, x, y, z)
+
+    /**
+     * Multiplies real number by quaternion.
+     *
+     * @receiver the multiplier.
+     * @param c the multiplicand.
+     * @receiver the product.
+     */
+    public operator fun Double.times(c: Quaternion): Quaternion =
+        Quaternion(this * c.w, this * c.x, this * c.y, this * c.z)
+
+    public override fun Quaternion.unaryMinus(): Quaternion = Quaternion(-w, -x, -y, -z)
+    public override fun norm(arg: Quaternion): Quaternion = sqrt(arg.conjugate * arg)
+
+    public override fun symbol(value: String): Quaternion = when (value) {
+        "i" -> i
+        "j" -> j
+        "k" -> k
+        else -> super<Field>.symbol(value)
+    }
+}
+
+/**
+ * Represents `double`-based quaternion.
+ *
+ * @property w The first component.
+ * @property x The second component.
+ * @property y The third component.
+ * @property z The fourth component.
+ */
+public data class Quaternion(val w: Double, val x: Double, val y: Double, val z: Double) :
+    FieldElement<Quaternion, Quaternion, QuaternionField>,
+    Comparable<Quaternion> {
+    public constructor(w: Number, x: Number, y: Number, z: Number) : this(
+        w.toDouble(),
+        x.toDouble(),
+        y.toDouble(),
+        z.toDouble()
+    )
+
+    public constructor(wx: Complex, yz: Complex) : this(wx.re, wx.im, yz.re, yz.im)
+
+    public override val context: QuaternionField
+        get() = QuaternionField
+
+    public override fun div(k: Number): Quaternion {
+        val d = k.toDouble()
+        return Quaternion(w / d, x / d, y / d, z / d)
+    }
+
+    public override fun unwrap(): Quaternion = this
+    public override fun Quaternion.wrap(): Quaternion = this
+    public override fun compareTo(other: Quaternion): Int = r.compareTo(other.r)
+    public override fun toString(): String = "($w + $x * i + $y * j + $z * k)"
+
+    public companion object : MemorySpec<Quaternion> {
+        public override val objectSize: Int
+            get() = 32
+
+        public override fun MemoryReader.read(offset: Int): Quaternion =
+            Quaternion(readDouble(offset), readDouble(offset + 8), readDouble(offset + 16), readDouble(offset + 24))
+
+        public override fun MemoryWriter.write(offset: Int, value: Quaternion) {
+            writeDouble(offset, value.w)
+            writeDouble(offset + 8, value.x)
+            writeDouble(offset + 16, value.y)
+            writeDouble(offset + 24, value.z)
+        }
+    }
+}
+
+/**
+ * Creates a quaternion with real part equal to this real.
+ *
+ * @receiver the real part.
+ * @return the new quaternion.
+ */
+public fun Number.toQuaternion(): Quaternion = Quaternion(this, 0, 0, 0)
+
+/**
+ * Creates a new buffer of quaternions with the specified [size], where each element is calculated by calling the
+ * specified [init] function.
+ */
+public inline fun Buffer.Companion.quaternion(size: Int, init: (Int) -> Quaternion): Buffer<Quaternion> =
+    MemoryBuffer.create(Quaternion, size, init)
+
+/**
+ * Creates a new buffer of quaternions with the specified [size], where each element is calculated by calling the
+ * specified [init] function.
+ */
+public inline fun MutableBuffer.Companion.quaternion(size: Int, init: (Int) -> Quaternion): MutableBuffer<Quaternion> =
+    MutableMemoryBuffer.create(Quaternion, size, init)