Make complex and quaternion NaN-hostile

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

@@ -57,26 +57,24 @@ public object ComplexField : ExtendedField<Complex>, Norm<Complex, Complex> {
         Complex(a.re * b.re - a.im * b.im, a.re * b.im + a.im * b.re)
 
     public override fun divide(a: Complex, b: Complex): Complex = when {
-        b.re.isNaN() || b.im.isNaN() -> Complex(Double.NaN, Double.NaN)
-
         abs(b.im) < abs(b.re) -> {
             val wr = b.im / b.re
             val wd = b.re + wr * b.im
 
             if (wd.isNaN() || wd == 0.0)
-                Complex(Double.NaN, Double.NaN)
+                throw ArithmeticException("Division by zero or infinity")
             else
                 Complex((a.re + a.im * wr) / wd, (a.im - a.re * wr) / wd)
         }
 
-        b.im == 0.0 -> Complex(Double.NaN, Double.NaN)
+        b.im == 0.0 -> throw ArithmeticException("Division by zero")
 
         else -> {
             val wr = b.re / b.im
             val wd = b.im + wr * b.re
 
             if (wd.isNaN() || wd == 0.0)
-                Complex(Double.NaN, Double.NaN)
+                throw ArithmeticException("Division by zero or infinity")
             else
                 Complex((a.re * wr + a.im) / wd, (a.im * wr - a.re) / wd)
         }
@@ -130,6 +128,11 @@ public data class Complex(val re: Double, val im: Double) : FieldElement<Complex
     public override val context: ComplexField
         get() = ComplexField
 
+    init {
+        require(!re.isNaN()) { "Real component of complex is not-a-number" }
+        require(!im.isNaN()) { "Imaginary component of complex is not-a-number" }
+    }
+
     public override fun unwrap(): Complex = this
     public override fun Complex.wrap(): Complex = this
     public override fun compareTo(other: Complex): Int = r.compareTo(other.r)

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

@@ -41,12 +41,12 @@ public object QuaternionField : Field<Quaternion>, Norm<Quaternion, Quaternion>,
     /**
      * The `i` quaternion unit.
      */
-    public val i: Quaternion by lazy { Quaternion(0, 1, 0, 0) }
+    public val i: Quaternion by lazy { Quaternion(0, 1) }
 
     /**
      * The `j` quaternion unit.
      */
-    public val j: Quaternion by lazy { Quaternion(0, 0, 1, 0) }
+    public val j: Quaternion by lazy { Quaternion(0, 0, 1) }
 
     /**
      * The `k` quaternion unit.
@@ -104,41 +104,23 @@ public object QuaternionField : Field<Quaternion>, Norm<Quaternion, Quaternion>,
         }
     }
 
-    private inline fun pwr2(x: Quaternion): Quaternion {
+    private 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
-        )
+        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 {
+    private 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
-        )
+        return Quaternion(x.w * (a2 - 3 * n1), x.x * n2, x.y * n2, x.z * n2)
     }
 
-    private inline fun pwr4(x: Quaternion): Quaternion {
+    private 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
-        )
+        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 {
@@ -213,6 +195,13 @@ public data class Quaternion(val w: Double, val x: Double, val y: Double, val z:
     public constructor(wx: Complex, yz: Complex) : this(wx.re, wx.im, yz.re, yz.im)
     public constructor(wx: Complex) : this(wx.re, wx.im, 0, 0)
 
+    init {
+        require(!w.isNaN()) { "w-component of quaternion is not-a-number" }
+        require(!x.isNaN()) { "x-component of quaternion is not-a-number" }
+        require(!y.isNaN()) { "x-component of quaternion is not-a-number" }
+        require(!z.isNaN()) { "x-component of quaternion is not-a-number" }
+    }
+
     public override val context: QuaternionField
         get() = QuaternionField
 

kmath-stat/build.gradle.kts

@@ -3,6 +3,13 @@ plugins {
 }
 
 kotlin.sourceSets {
+    all {
+        languageSettings.apply {
+            useExperimentalAnnotation("kotlinx.coroutines.FlowPreview")
+            useExperimentalAnnotation("kotlinx.coroutines.ExperimentalCoroutinesApi")
+        }
+    }
+
     commonMain {
         dependencies {
             api(project(":kmath-coroutines"))