A simpler 'Array<*>.toF64Array'

CHANGES

@@ -10,7 +10,7 @@ Version 0.4.0
 - Allowed slicing a `StridedVector` with custom `step`.
 - Replaced `Strided` prefix with `F64`.
 - Removed specialcased 'Vector', `Matrix2` and `Matrix3` classes in
-  faviour of a more generic `F64Array`.
+  favour of a more generic `F64Array`.
 - Added a special attribute `V` for slicing the array.
 - Removed `stochastic` and `indexedStochastic`.
 - Added `axis` to `F64Array.append`, `F64Array.slice` and `F64Array.reorder`.

src/main/kotlin/org/jetbrains/bio/viktor/F64Array.kt

@@ -757,26 +757,18 @@ fun DoubleArray.asF64Array(offset: Int = 0, size: Int = this.size): F64Array {
 /** Copies the elements of this nested array into [F64Array] of the same shape. */
 fun Array<*>.toF64Array(): F64Array {
     val shape = guessShape()
-    val a = F64Array(shape.product())
-
-    var ptr = 0
-    val q = ArrayDeque<Any>()
-    q.add(this)
-
-    do {
-        val tip = q.removeFirst()
-        when (tip) {
-            is DoubleArray -> {
-                tip.asF64Array().copyTo(a.slice(ptr, ptr + tip.size))
-                ptr += tip.size
-            }
-            is Array<*> -> q.addAll(tip)
+    return flatten(this).asF64Array().reshape(*shape)
+}
+
+/** Flattens a nested [DoubleArray]. */
+private fun flatten(a: Array<*>): DoubleArray {
+    return Arrays.stream(a).flatMapToDouble {
+        when (it) {
+            is DoubleArray -> Arrays.stream(it)
+            is Array<*> -> Arrays.stream(flatten(a))
             else -> unsupported()
         }
-
-    } while (q.isNotEmpty())
-
-    return a.reshape(*shape)
+    }.toArray()
 }
 
 /** No validation, therefore "check". */