value method for algebra

kmath-noa/src/main/kotlin/space/kscience/kmath/noa/algebras.kt

@@ -11,16 +11,26 @@ import space.kscience.kmath.tensors.api.LinearOpsTensorAlgebra
 import space.kscience.kmath.tensors.api.Tensor
 import space.kscience.kmath.tensors.api.TensorAlgebra
 
-public abstract class NoaAlgebra<T, TensorType: NoaTensor<T>>
-internal constructor(protected val scope: NoaScope)
-    : TensorAlgebra<T>  {
+
+public sealed class NoaAlgebra<T, TensorType : NoaTensor<T>>
+constructor(protected val scope: NoaScope) : TensorAlgebra<T> {
 
     protected abstract fun Tensor<T>.cast(): TensorType
+
+    protected abstract fun wrap(tensorHandle: TensorHandle): TensorType
+
+    /**
+     * A scalar tensor in this implementation must have empty shape
+     */
+    override fun Tensor<T>.valueOrNull(): T? =
+        try { this.cast().item() } catch (e: NoaException) { null }
+
+    override fun Tensor<T>.value(): T = this.cast().item()
 }
 
-public abstract class NoaPartialDivisionAlgebra<T, TensorType: NoaTensor<T>>
-internal constructor(scope: NoaScope)
-    : NoaAlgebra<T, TensorType>(scope), LinearOpsTensorAlgebra<T>, AnalyticTensorAlgebra<T> {
+public abstract class NoaPartialDivisionAlgebra<T, TensorType : NoaTensor<T>>
+internal constructor(scope: NoaScope) : NoaAlgebra<T, TensorType>(scope), LinearOpsTensorAlgebra<T>,
+    AnalyticTensorAlgebra<T> {
 
 
 }

kmath-noa/src/main/kotlin/space/kscience/kmath/noa/tensors.kt

@@ -19,6 +19,8 @@ constructor(scope: NoaScope, internal val tensorHandle: TensorHandle) :
 
     override fun dispose(): Unit = JNoa.disposeTensor(tensorHandle)
 
+    internal abstract fun item(): T
+
     override val dimension: Int get() = JNoa.getDim(tensorHandle)
 
     override val shape: IntArray
@@ -79,7 +81,7 @@ public class NoaDoubleTensor
 internal constructor(scope: NoaScope, tensorHandle: TensorHandle) :
     NoaTensorOverField<Double>(scope, tensorHandle) {
 
-    internal fun item(): Double = JNoa.getItemDouble(tensorHandle)
+    override fun item(): Double = JNoa.getItemDouble(tensorHandle)
 
     @PerformancePitfall
     override fun get(index: IntArray): Double = JNoa.getDouble(tensorHandle, index)
@@ -94,7 +96,7 @@ public class NoaFloatTensor
 internal constructor(scope: NoaScope, tensorHandle: TensorHandle) :
     NoaTensorOverField<Float>(scope, tensorHandle) {
 
-    internal fun item(): Float = JNoa.getItemFloat(tensorHandle)
+    override fun item(): Float = JNoa.getItemFloat(tensorHandle)
 
     @PerformancePitfall
     override fun get(index: IntArray): Float = JNoa.getFloat(tensorHandle, index)
@@ -109,7 +111,7 @@ public class NoaLongTensor
 internal constructor(scope: NoaScope, tensorHandle: TensorHandle) :
     NoaTensor<Long>(scope, tensorHandle) {
 
-    internal fun item(): Long = JNoa.getItemLong(tensorHandle)
+    override fun item(): Long = JNoa.getItemLong(tensorHandle)
 
     @PerformancePitfall
     override fun get(index: IntArray): Long = JNoa.getLong(tensorHandle, index)
@@ -124,7 +126,7 @@ public class NoaIntTensor
 internal constructor(scope: NoaScope, tensorHandle: TensorHandle) :
     NoaTensor<Int>(scope, tensorHandle) {
 
-    internal fun item(): Int = JNoa.getItemInt(tensorHandle)
+    override fun item(): Int = JNoa.getItemInt(tensorHandle)
 
     @PerformancePitfall
     override fun get(index: IntArray): Int = JNoa.getInt(tensorHandle, index)

kmath-tensors/src/commonMain/kotlin/space/kscience/kmath/tensors/api/TensorAlgebra.kt

@@ -16,19 +16,19 @@ import space.kscience.kmath.operations.Algebra
 public interface TensorAlgebra<T> : Algebra<Tensor<T>> {
 
     /**
-     * Returns a single tensor value of unit dimension if tensor shape equals to [1].
+     * For a tensor containing a single element, i.e. a scalar tensor, the value of that element is returned.
+     * You need to check if the implementation puts any restrictions on the shape of a scalar tensor.
      *
      * @return a nullable value of a potentially scalar tensor.
      */
     public fun Tensor<T>.valueOrNull(): T?
 
     /**
-     * Returns a single tensor value of unit dimension. The tensor shape must be equal to [1].
+     * Unsafe version of [valueOrNull]
      *
      * @return the value of a scalar tensor.
      */
-    public fun Tensor<T>.value(): T =
-        valueOrNull() ?: throw IllegalArgumentException("Inconsistent value for tensor of with $shape shape")
+    public fun Tensor<T>.value(): T
 
     /**
      * Each element of the tensor [other] is added to this value.

kmath-tensors/src/commonMain/kotlin/space/kscience/kmath/tensors/core/DoubleTensorAlgebra.kt

@@ -24,9 +24,20 @@ public open class DoubleTensorAlgebra :
 
     public companion object : DoubleTensorAlgebra()
 
+
+    /**
+     * Returns a single tensor value of unit dimension if tensor shape equals to [1].
+     *
+     * @return a nullable value of a potentially scalar tensor.
+     */
     override fun Tensor<Double>.valueOrNull(): Double? = if (tensor.shape contentEquals intArrayOf(1))
         tensor.mutableBuffer.array()[tensor.bufferStart] else null
 
+    /**
+     * Returns a single tensor value of unit dimension. The tensor shape must be equal to [1].
+     *
+     * @return the value of a scalar tensor.
+     */
     override fun Tensor<Double>.value(): Double = valueOrNull()
         ?: throw IllegalArgumentException("The tensor shape is $shape, but value method is allowed only for shape [1]")