[WIP] Refactor NDStructures

examples/src/main/kotlin/kscience/kmath/operations/ComplexDemo.kt

@@ -1,17 +1,17 @@
 package kscience.kmath.operations
 
-import kscience.kmath.nd.NDField
+import kscience.kmath.nd.NDAlgebra
-import kscience.kmath.structures.NDElement
+import kscience.kmath.nd.complex
 
 fun main() {
     // 2d element
-    val element = NDElement.complex(2, 2) { (i,j) ->
+    val element = NDAlgebra.complex(2, 2).produce { (i,j) ->
         Complex(i.toDouble() - j.toDouble(), i.toDouble() + j.toDouble())
     }
     println(element)
 
     // 1d element operation
-    val result = with(NDField.complex(8)) {
+    val result = with(NDAlgebra.complex(8)) {
         val a = produce { (it) -> i * it - it.toDouble() }
         val b = 3
         val c = Complex(1.0, 1.0)

examples/src/main/kotlin/kscience/kmath/structures/NDField.kt

@@ -1,7 +1,10 @@
 package kscience.kmath.structures
 
 import kotlinx.coroutines.GlobalScope
-import kscience.kmath.nd.*
+import kscience.kmath.nd.NDAlgebra
+import kscience.kmath.nd.NDStructure
+import kscience.kmath.nd.field
+import kscience.kmath.nd.real
 import kscience.kmath.nd4j.Nd4jArrayField
 import kscience.kmath.operations.RealField
 import kscience.kmath.operations.invoke
@@ -39,8 +42,10 @@ fun main() {
     }
 
     measureAndPrint("Element addition") {
-        var res: NDStructure<Double> = boxingField.one
+        boxingField {
-        repeat(n) { res += 1.0 }
+        var res: NDStructure<Double> = one
+            repeat(n) { res += 1.0 }
+        }
     }
 
     measureAndPrint("Specialized addition") {
@@ -52,7 +57,7 @@ fun main() {
 
     measureAndPrint("Nd4j specialized addition") {
         nd4jField {
-            var res = one
+            var res:NDStructure<Double> = one
             repeat(n) { res += 1.0 }
         }
     }

kmath-commons/src/main/kotlin/kscience/kmath/commons/linear/CMMatrix.kt

@@ -1,10 +1,7 @@
 package kscience.kmath.commons.linear
 
-import kscience.kmath.linear.DiagonalFeature
+import kscience.kmath.linear.*
-import kscience.kmath.linear.MatrixContext
-import kscience.kmath.linear.Point
 import kscience.kmath.misc.UnstableKMathAPI
-import kscience.kmath.nd.Matrix
 import org.apache.commons.math3.linear.*
 import kotlin.reflect.KClass
 import kotlin.reflect.cast

kmath-commons/src/main/kotlin/kscience/kmath/commons/linear/CMSolver.kt

@@ -1,7 +1,7 @@
 package kscience.kmath.commons.linear
 
+import kscience.kmath.linear.Matrix
 import kscience.kmath.linear.Point
-import kscience.kmath.nd.Matrix
 import org.apache.commons.math3.linear.*
 
 public enum class CMDecomposition {

kmath-core/src/commonMain/kotlin/kscience/kmath/nd/BufferNDAlgebra.kt

@@ -86,7 +86,7 @@ public fun <T, A : Space<T>> NDAlgebra.Companion.space(
     vararg shape: Int,
 ): BufferedNDSpace<T, A> = BufferedNDSpace(shape, space, bufferFactory)
 
-public inline fun <T, A : Space<T>, R> A.nd(
+public inline fun <T, A : Space<T>, R> A.ndSpace(
     noinline bufferFactory: BufferFactory<T>,
     vararg shape: Int,
     action: BufferedNDSpace<T, A>.() -> R,
@@ -102,7 +102,7 @@ public fun <T, A : Ring<T>> NDAlgebra.Companion.ring(
     vararg shape: Int,
 ): BufferedNDRing<T, A> = BufferedNDRing(shape, ring, bufferFactory)
 
-public inline fun <T, A : Ring<T>, R> A.nd(
+public inline fun <T, A : Ring<T>, R> A.ndRing(
     noinline bufferFactory: BufferFactory<T>,
     vararg shape: Int,
     action: BufferedNDRing<T, A>.() -> R,
@@ -118,7 +118,7 @@ public fun <T, A : Field<T>> NDAlgebra.Companion.field(
     vararg shape: Int,
 ): BufferedNDField<T, A> = BufferedNDField(shape, field, bufferFactory)
 
-public inline fun <T, A : Field<T>, R> A.nd(
+public inline fun <T, A : Field<T>, R> A.ndField(
     noinline bufferFactory: BufferFactory<T>,
     vararg shape: Int,
     action: BufferedNDField<T, A>.() -> R,

kmath-core/src/commonMain/kotlin/kscience/kmath/nd/RealNDField.kt

@@ -94,9 +94,12 @@ public open class RealNDField(
 /**
  * Fast element production using function inlining
  */
-public inline fun BufferedNDField<Double, RealField>.produceInline(crossinline initializer: RealField.(Int) -> Double): NDBuffer<Double> {
+public inline fun BufferedNDField<Double, RealField>.produceInline(crossinline initializer: RealField.(IntArray) -> Double): NDBuffer<Double> {
     contract { callsInPlace(initializer, InvocationKind.EXACTLY_ONCE) }
-    val array = DoubleArray(strides.linearSize) { offset -> RealField.initializer(offset) }
+    val array = DoubleArray(strides.linearSize) { offset ->
+        val index = strides.index(offset)
+        RealField.initializer(index)
+    }
     return NDBuffer(strides, RealBuffer(array))
 }
 

kmath-core/src/commonMain/kotlin/kscience/kmath/nd/Structure2D.kt

@@ -52,7 +52,15 @@ public interface Structure2D<T> : NDStructure<T> {
             for (j in 0 until colNum) yield(intArrayOf(i, j) to get(i, j))
     }
 
-    public companion object
+    public companion object {
+        public inline fun real(
+            rows: Int,
+            columns: Int,
+            crossinline init: (i: Int, j: Int) -> Double,
+        ): NDBuffer<Double> = NDAlgebra.real(rows, columns).produceInline { (i, j) ->
+            init(i, j)
+        }
+    }
 }
 
 /**

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

@@ -1,10 +1,12 @@
 package kscience.kmath.operations
 
 import kscience.kmath.misc.UnstableKMathAPI
+import kscience.kmath.nd.BufferedNDRing
 import kscience.kmath.nd.NDAlgebra
 import kscience.kmath.operations.BigInt.Companion.BASE
 import kscience.kmath.operations.BigInt.Companion.BASE_SIZE
-import kscience.kmath.structures.*
+import kscience.kmath.structures.Buffer
+import kscience.kmath.structures.MutableBuffer
 import kotlin.math.log2
 import kotlin.math.max
 import kotlin.math.min
@@ -463,10 +465,5 @@ public inline fun Buffer.Companion.bigInt(size: Int, initializer: (Int) -> BigIn
 public inline fun MutableBuffer.Companion.bigInt(size: Int, initializer: (Int) -> BigInt): MutableBuffer<BigInt> =
     boxing(size, initializer)
 
-public fun NDAlgebra.Companion.bigInt(vararg shape: Int): BoxingNDRing<BigInt, BigIntField> =
+public fun NDAlgebra.Companion.bigInt(vararg shape: Int): BufferedNDRing<BigInt, BigIntField> =
-    BoxingNDRing(shape, BigIntField, Buffer.Companion::bigInt)
+    BufferedNDRing(shape, BigIntField, Buffer.Companion::bigInt)
-
-public fun NDElement.Companion.bigInt(
-    vararg shape: Int,
-    initializer: BigIntField.(IntArray) -> BigInt
-): BufferedNDRingElement<BigInt, BigIntField> = NDAlgebra.bigInt(*shape).produce(initializer)

kmath-core/src/commonMain/kotlin/kscience/kmath/structures/Buffers.kt

@@ -43,7 +43,7 @@ public interface Buffer<T> {
      * Checks content equality with another buffer.
      */
     public fun contentEquals(other: Buffer<*>): Boolean =
-        kscience.kmath.nd.mapIndexed { index, value -> value == other[index] }.all { it }
+        asSequence().mapIndexed { index, value -> value == other[index] }.all { it }
 
     public companion object {
         /**

kmath-core/src/commonMain/kotlin/kscience/kmath/structures/FlaggedBuffer.kt

@@ -60,7 +60,7 @@ public class FlaggedRealBuffer(public val values: DoubleArray, public val flags:
 
     override operator fun get(index: Int): Double? = if (isValid(index)) values[index] else null
 
-    override operator fun iterator(): Iterator<Double?> = kscience.kmath.nd.map {
+    override operator fun iterator(): Iterator<Double?> = values.indices.asSequence().map {
         if (isValid(it)) values[it] else null
     }.iterator()
 }

kmath-core/src/commonMain/kotlin/kscience/kmath/structures/MemoryBuffer.kt

@@ -15,7 +15,7 @@ public open class MemoryBuffer<T : Any>(protected val memory: Memory, protected
     private val reader: MemoryReader = memory.reader()
 
     override operator fun get(index: Int): T = reader.read(spec, spec.objectSize * index)
-    override operator fun iterator(): Iterator<T> = kscience.kmath.nd.map { get(it) }.iterator()
+    override operator fun iterator(): Iterator<T> = (0 until size).asSequence().map { get(it) }.iterator()
 
     public companion object {
         public fun <T : Any> create(spec: MemorySpec<T>, size: Int): MemoryBuffer<T> =

kmath-core/src/commonTest/kotlin/kscience/kmath/structures/NDFieldTest.kt

@@ -1,6 +1,8 @@
 package kscience.kmath.structures
 
-import kscience.kmath.nd.NDField
+import kscience.kmath.nd.NDAlgebra
+import kscience.kmath.nd.get
+import kscience.kmath.nd.real
 import kscience.kmath.operations.internal.FieldVerifier
 import kotlin.test.Test
 import kotlin.test.assertEquals
@@ -8,12 +10,12 @@ import kotlin.test.assertEquals
 internal class NDFieldTest {
     @Test
     fun verify() {
-        NDField.real(12, 32).run { FieldVerifier(this, one + 3, one - 23, one * 12, 6.66) }
+        NDAlgebra.real(12, 32).run { FieldVerifier(this, one + 3, one - 23, one * 12, 6.66) }
     }
 
     @Test
     fun testStrides() {
-        val ndArray = NDElement.real(intArrayOf(10, 10)) { (it[0] + it[1]).toDouble() }
+        val ndArray = NDAlgebra.real(10, 10).produce { (it[0] + it[1]).toDouble() }
         assertEquals(ndArray[5, 5], 10.0)
     }
 }

kmath-core/src/commonTest/kotlin/kscience/kmath/structures/NumberNDFieldTest.kt

@@ -1,9 +1,8 @@
 package kscience.kmath.structures
 
-import kscience.kmath.nd.NDField
+import kscience.kmath.nd.*
-import kscience.kmath.nd.NDStructure
 import kscience.kmath.operations.Norm
-import kscience.kmath.structures.NDElement.Companion.real2D
+import kscience.kmath.operations.invoke
 import kotlin.math.abs
 import kotlin.math.pow
 import kotlin.test.Test
@@ -11,25 +10,30 @@ import kotlin.test.assertEquals
 
 @Suppress("UNUSED_VARIABLE")
 class NumberNDFieldTest {
-    val array1: RealNDElement = real2D(3, 3) { i, j -> (i + j).toDouble() }
+    val algebra = NDAlgebra.real(3,3)
-    val array2: RealNDElement = real2D(3, 3) { i, j -> (i - j).toDouble() }
+    val array1 = algebra.produceInline { (i, j) -> (i + j).toDouble() }
+    val array2 = algebra.produceInline { (i, j) -> (i - j).toDouble() }
 
     @Test
     fun testSum() {
-        val sum = array1 + array2
+        algebra {
-        assertEquals(4.0, sum[2, 2])
+            val sum = array1 + array2
+            assertEquals(4.0, sum[2, 2])
+        }
     }
 
     @Test
     fun testProduct() {
-        val product = array1 * array2
+        algebra {
-        assertEquals(0.0, product[2, 2])
+            val product = array1 * array2
+            assertEquals(0.0, product[2, 2])
+        }
     }
 
     @Test
     fun testGeneration() {
 
-        val array = real2D(3, 3) { i, j -> (i * 10 + j).toDouble() }
+        val array = Structure2D.real(3, 3) { i, j -> (i * 10 + j).toDouble() }
 
         for (i in 0..2) {
             for (j in 0..2) {
@@ -41,16 +45,20 @@ class NumberNDFieldTest {
 
     @Test
     fun testExternalFunction() {
-        val function: (Double) -> Double = { x -> x.pow(2) + 2 * x + 1 }
+        algebra {
-        val result = function(array1) + 1.0
+            val function: (Double) -> Double = { x -> x.pow(2) + 2 * x + 1 }
-        assertEquals(10.0, result[1, 1])
+            val result = function(array1) + 1.0
+            assertEquals(10.0, result[1, 1])
+        }
     }
 
     @Test
     fun testLibraryFunction() {
-        val abs: (Double) -> Double = ::abs
+        algebra {
-        val result = abs(array2)
+            val abs: (Double) -> Double = ::abs
-        assertEquals(2.0, result[0, 2])
+            val result = abs(array2)
+            assertEquals(2.0, result[0, 2])
+        }
     }
 
     @Test
@@ -65,6 +73,8 @@ class NumberNDFieldTest {
 
     @Test
     fun testInternalContext() {
-        (NDField.real(*array1.shape)) { with(L2Norm) { 1 + norm(array1) + exp(array2) } }
+        algebra {
+            (NDAlgebra.real(*array1.shape)) { with(L2Norm) { 1 + norm(array1) + exp(array2) } }
+        }
     }
 }

kmath-coroutines/src/jvmMain/kotlin/kscience/kmath/structures/LazyNDStructure.kt

@@ -21,7 +21,7 @@ public class LazyNDStructure<T>(
 
     public override fun elements(): Sequence<Pair<IntArray, T>> {
         val strides = DefaultStrides(shape)
-        val res = runBlocking { kscience.kmath.nd.map { index -> index to await(index) } }
+        val res = runBlocking { strides.indices().toList().map { index -> index to await(index) } }
         return res.asSequence()
     }
 

kmath-ejml/src/main/kotlin/kscience/kmath/ejml/EjmlMatrixContext.kt

@@ -1,10 +1,7 @@
 package kscience.kmath.ejml
 
-import kscience.kmath.linear.InverseMatrixFeature
+import kscience.kmath.linear.*
-import kscience.kmath.linear.MatrixContext
-import kscience.kmath.linear.Point
 import kscience.kmath.misc.UnstableKMathAPI
-import kscience.kmath.nd.Matrix
 import kscience.kmath.nd.getFeature
 import org.ejml.simple.SimpleMatrix
 

kmath-for-real/src/commonMain/kotlin/kscience/kmath/real/RealMatrix.kt

@@ -1,11 +1,11 @@
 package kscience.kmath.real
 
-import kscience.kmath.linear.MatrixContext
+import kscience.kmath.linear.*
-import kscience.kmath.linear.real
 import kscience.kmath.misc.UnstableKMathAPI
-import kscience.kmath.nd.Matrix
 import kscience.kmath.structures.Buffer
 import kscience.kmath.structures.RealBuffer
+import kscience.kmath.structures.asIterable
+import kotlin.math.pow
 
 /*
  *  Functions for convenient "numpy-like" operations with Double matrices.

kmath-for-real/src/commonTest/kotlin/kaceince/kmath/real/RealMatrixTest.kt

@@ -1,7 +1,9 @@
 package kaceince.kmath.real
 
-import kscience.kmath.nd.Matrix
+import kscience.kmath.linear.Matrix
+import kscience.kmath.linear.build
 import kscience.kmath.real.*
+import kscience.kmath.structures.contentEquals
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertTrue

kmath-histograms/src/commonMain/kotlin/kscience/kmath/histogram/RealHistogram.kt

@@ -17,7 +17,7 @@ public data class BinDef<T : Comparable<T>>(
         require(vector.size == center.size) { "Dimension mismatch for input vector. Expected ${center.size}, but found ${vector.size}" }
         val upper = space { center + sizes / 2.0 }
         val lower = space { center - sizes / 2.0 }
-        return kscience.kmath.nd.mapIndexed { i, value -> value in lower[i]..upper[i] }.all { it }
+        return vector.asSequence().mapIndexed { i, value -> value in lower[i]..upper[i] }.all { it }
     }
 }
 
@@ -70,7 +70,7 @@ public class RealHistogram(
     public fun getValue(point: Buffer<out Double>): Long = getValue(getIndex(point))
 
     private fun getDef(index: IntArray): BinDef<Double> {
-        val center = kscience.kmath.nd.mapIndexed { axis, i ->
+        val center = index.mapIndexed { axis, i ->
             when (i) {
                 0 -> Double.NEGATIVE_INFINITY
                 strides.shape[axis] - 1 -> Double.POSITIVE_INFINITY
@@ -100,7 +100,7 @@ public class RealHistogram(
     }
 
     public override operator fun iterator(): Iterator<MultivariateBin<Double>> =
-        kscience.kmath.nd.map { (index, value) -> MultivariateBin(getDef(index), value.sum()) }
+        weights.elements().map { (index, value) -> MultivariateBin(getDef(index), value.sum()) }
             .iterator()
 
     /**

kmath-nd4j/src/main/kotlin/kscience.kmath.nd4j/Nd4jArrayAlgebra.kt

@@ -7,6 +7,13 @@ import kscience.kmath.structures.*
 import org.nd4j.linalg.api.ndarray.INDArray
 import org.nd4j.linalg.factory.Nd4j
 
+internal fun NDAlgebra<*, *>.checkShape(array: INDArray): INDArray {
+    val arrayShape = array.shape().toIntArray()
+    if (!shape.contentEquals(arrayShape)) throw ShapeMismatchException(shape, arrayShape)
+    return array
+}
+
+
 /**
  * Represents [NDAlgebra] over [Nd4jArrayAlgebra].
  *
@@ -18,8 +25,9 @@ public interface Nd4jArrayAlgebra<T, C> : NDAlgebra<T, C> {
      * Wraps [INDArray] to [N].
      */
     public fun INDArray.wrap(): Nd4jArrayStructure<T>
+
     public val NDStructure<T>.ndArray: INDArray
-        get() = when  {
+        get() = when {
             !shape.contentEquals(this@Nd4jArrayAlgebra.shape) -> throw ShapeMismatchException(
                 this@Nd4jArrayAlgebra.shape,
                 shape
@@ -213,7 +221,7 @@ public class RealNd4jArrayField(public override val shape: IntArray) : Nd4jArray
     public override val elementContext: RealField
         get() = RealField
 
-    public override fun INDArray.wrap(): Nd4jArrayStructure<Double> = checkShape(asRealStructure())
+    public override fun INDArray.wrap(): Nd4jArrayStructure<Double> = checkShape(this).asRealStructure()
 
     public override operator fun NDStructure<Double>.div(arg: Double): Nd4jArrayStructure<Double> {
         return ndArray.div(arg).wrap()
@@ -247,7 +255,7 @@ public class FloatNd4jArrayField(public override val shape: IntArray) : Nd4jArra
     public override val elementContext: FloatField
         get() = FloatField
 
-    public override fun INDArray.wrap(): Nd4jArrayStructure<Float> = checkShape(asFloatStructure())
+    public override fun INDArray.wrap(): Nd4jArrayStructure<Float> = checkShape(this).asFloatStructure()
 
     public override operator fun NDStructure<Float>.div(arg: Float): Nd4jArrayStructure<Float> {
         return ndArray.div(arg).wrap()
@@ -281,7 +289,7 @@ public class IntNd4jArrayRing(public override val shape: IntArray) : Nd4jArrayRi
     public override val elementContext: IntRing
         get() = IntRing
 
-    public override fun INDArray.wrap(): Nd4jArrayStructure<Int> = check(asIntStructure())
+    public override fun INDArray.wrap(): Nd4jArrayStructure<Int> = checkShape(this).asIntStructure()
 
     public override operator fun NDStructure<Int>.plus(arg: Int): Nd4jArrayStructure<Int> {
         return ndArray.add(arg).wrap()
@@ -307,7 +315,7 @@ public class LongNd4jArrayRing(public override val shape: IntArray) : Nd4jArrayR
     public override val elementContext: LongRing
         get() = LongRing
 
-    public override fun INDArray.wrap(): Nd4jArrayStructure<Long> = check(asLongStructure())
+    public override fun INDArray.wrap(): Nd4jArrayStructure<Long> = checkShape(this).asLongStructure()
 
     public override operator fun NDStructure<Long>.plus(arg: Long): Nd4jArrayStructure<Long> {
         return ndArray.add(arg).wrap()

kmath-viktor/src/main/kotlin/kscience/kmath/viktor/ViktorNDStructure.kt

@@ -1,9 +1,6 @@
 package kscience.kmath.viktor
 
-import kscience.kmath.nd.DefaultStrides
+import kscience.kmath.nd.*
-import kscience.kmath.nd.MutableNDStructure
-import kscience.kmath.nd.NDField
-import kscience.kmath.nd.Strides
 import kscience.kmath.operations.RealField
 import org.jetbrains.bio.viktor.F64Array
 
@@ -24,14 +21,25 @@ public inline class ViktorNDStructure(public val f64Buffer: F64Array) : MutableN
 public fun F64Array.asStructure(): ViktorNDStructure = ViktorNDStructure(this)
 
 @Suppress("OVERRIDE_BY_INLINE", "NOTHING_TO_INLINE")
-public class ViktorNDField(public override val shape: IntArray) : NDField<Double, RealField, ViktorNDStructure> {
+public class ViktorNDField(public override val shape: IntArray) : NDField<Double, RealField> {
+
+    public val NDStructure<Double>.f64Buffer: F64Array
+        get() = when {
+            !shape.contentEquals(this@ViktorNDField.shape) -> throw ShapeMismatchException(
+                this@ViktorNDField.shape,
+                shape
+            )
+            this is ViktorNDStructure && this.f64Buffer.shape.contentEquals(this@ViktorNDField.shape) -> this.f64Buffer
+            else -> produce { this@f64Buffer[it] }.f64Buffer
+        }
+
     public override val zero: ViktorNDStructure
         get() = F64Array.full(init = 0.0, shape = shape).asStructure()
 
     public override val one: ViktorNDStructure
         get() = F64Array.full(init = 1.0, shape = shape).asStructure()
 
-    public val strides: Strides = DefaultStrides(shape)
+    private val strides: Strides = DefaultStrides(shape)
 
     public override val elementContext: RealField get() = RealField
 
@@ -42,7 +50,7 @@ public class ViktorNDField(public override val shape: IntArray) : NDField<Double
             }
         }.asStructure()
 
-    public override fun map(arg: ViktorNDStructure, transform: RealField.(Double) -> Double): ViktorNDStructure =
+    public override fun map(arg: NDStructure<Double>, transform: RealField.(Double) -> Double): ViktorNDStructure =
         F64Array(*shape).apply {
             this@ViktorNDField.strides.indices().forEach { index ->
                 set(value = RealField.transform(arg[index]), indices = index)
@@ -50,7 +58,7 @@ public class ViktorNDField(public override val shape: IntArray) : NDField<Double
         }.asStructure()
 
     public override fun mapIndexed(
-        arg: ViktorNDStructure,
+        arg: NDStructure<Double>,
         transform: RealField.(index: IntArray, Double) -> Double
     ): ViktorNDStructure = F64Array(*shape).apply {
         this@ViktorNDField.strides.indices().forEach { index ->
@@ -59,8 +67,8 @@ public class ViktorNDField(public override val shape: IntArray) : NDField<Double
     }.asStructure()
 
     public override fun combine(
-        a: ViktorNDStructure,
+        a: NDStructure<Double>,
-        b: ViktorNDStructure,
+        b: NDStructure<Double>,
         transform: RealField.(Double, Double) -> Double
     ): ViktorNDStructure = F64Array(*shape).apply {
         this@ViktorNDField.strides.indices().forEach { index ->
@@ -68,21 +76,21 @@ public class ViktorNDField(public override val shape: IntArray) : NDField<Double
         }
     }.asStructure()
 
-    public override fun add(a: ViktorNDStructure, b: ViktorNDStructure): ViktorNDStructure =
+    public override fun add(a: NDStructure<Double>, b: NDStructure<Double>): ViktorNDStructure =
         (a.f64Buffer + b.f64Buffer).asStructure()
 
-    public override fun multiply(a: ViktorNDStructure, k: Number): ViktorNDStructure =
+    public override fun multiply(a: NDStructure<Double>, k: Number): ViktorNDStructure =
         (a.f64Buffer * k.toDouble()).asStructure()
 
-    public override inline fun ViktorNDStructure.plus(b: ViktorNDStructure): ViktorNDStructure =
+    public override inline fun NDStructure<Double>.plus(b: NDStructure<Double>): ViktorNDStructure =
         (f64Buffer + b.f64Buffer).asStructure()
 
-    public override inline fun ViktorNDStructure.minus(b: ViktorNDStructure): ViktorNDStructure =
+    public override inline fun NDStructure<Double>.minus(b: NDStructure<Double>): ViktorNDStructure =
         (f64Buffer - b.f64Buffer).asStructure()
 
-    public override inline fun ViktorNDStructure.times(k: Number): ViktorNDStructure =
+    public override inline fun NDStructure<Double>.times(k: Number): ViktorNDStructure =
         (f64Buffer * k.toDouble()).asStructure()
 
-    public override inline fun ViktorNDStructure.plus(arg: Double): ViktorNDStructure =
+    public override inline fun NDStructure<Double>.plus(arg: Double): ViktorNDStructure =
         (f64Buffer.plus(arg)).asStructure()
 }