Add default parameters for Scala NDArray.arange

scala-package/core/src/main/scala/org/apache/mxnet/NDArray.scala

@@ -405,15 +405,13 @@ object NDArray extends NDArrayBase {
    * @param stop End of interval.
    * @param step Spacing between values. The default step size is 1.
    * @param repeat Number of times to repeat each element. The default repeat count is 1.
-   * @param infer_range
-   *          When set to True, infer the stop position from the start, step,
-   *          repeat, and output tensor size.
    * @param ctx Device context. Default context is the current default context.
    * @param dType The data type of the `NDArray`. The default datatype is `DType.Float32`.
    * @return NDArray of evenly spaced values in the specified range.
    */
-  def arange(start: Float, stop: Option[Float], step: Float,
-             repeat: Int, ctx: Context, dType: DType): NDArray = {
+  def arange(start: Float, stop: Option[Float] = None, step: Float = 1.0f,
+             repeat: Int = 1, ctx: Context = Context.defaultCtx,
+             dType: DType = Base.MX_REAL_TYPE): NDArray = {
     val params = Map("start" -> start, "step" -> step, "repeat" -> repeat,
       "infer_range" -> false, "ctx" -> ctx.toString, "dtype" -> dType.toString())
     val fParams = if (stop == None) params else params ++ Map("stop" -> stop.get)

scala-package/core/src/test/scala/org/apache/mxnet/NDArraySuite.scala

@@ -167,11 +167,21 @@ class NDArraySuite extends FunSuite with BeforeAndAfterAll with Matchers {
       val stop = start + scala.util.Random.nextFloat() * 100
       val step = scala.util.Random.nextFloat() * 4
       val repeat = 1
-      val result = (start.toDouble until stop.toDouble by step.toDouble)
-              .flatMap(x => Array.fill[Float](repeat)(x.toFloat))
-      val range = NDArray.arange(start = start, stop = Some(stop), step = step,
-        repeat = repeat, ctx = Context.cpu(), dType = DType.Float32)
-      assert(CheckUtils.reldiff(result.toArray, range.toArray) <= 1e-4f)
+
+      val result1 = (start.toDouble until stop.toDouble by step.toDouble)
+        .flatMap(x => Array.fill[Float](repeat)(x.toFloat))
+      val range1 = NDArray.arange(start = start, stop = Some(stop), step = step,
+        repeat = repeat)
+      assert(CheckUtils.reldiff(result1.toArray, range1.toArray) <= 1e-4f)
+
+      val result2 = (0.0 until stop.toDouble by step.toDouble)
+        .flatMap(x => Array.fill[Float](repeat)(x.toFloat))
+      val range2 = NDArray.arange(stop, step = step, repeat = repeat)
+      assert(CheckUtils.reldiff(result2.toArray, range2.toArray) <= 1e-4f)
+
+      val result3 = 0f to stop by 1f
+      val range3 = NDArray.arange(stop)
+      assert(CheckUtils.reldiff(result3.toArray, range3.toArray) <= 1e-4f)
     }
   }