refactor: reduce code duplication and add comments

Signed-off-by: Athan <kgryte@gmail.com>

Author: kgryte

lib/node_modules/@stdlib/blas/ext/base/ddiff/lib/ndarray.js

@@ -76,12 +76,11 @@ function ddiff( N, k, x, strideX, offsetX, N1, prepend, strideP, offsetP, N2, ap
 	if ( total <= 1 ) {
 		return out;
 	}
-
-	// If k >= total number of elements, the k-th forward difference results in an empty array, so this function is a no-op...
+	// If `k` is greater than or equal to the total number of elements, the k-th forward difference results in an empty array, so this function is a no-op...
 	if ( k >= total ) {
 		return out;
 	}
-
+	// If `k` is equal to zero, there are no differences to compute, so we merely copy the various arrays into the output array...
 	if ( k === 0 ) {
 		// Copy `prepend` into output array:
 		dcopy( N1, prepend, strideP, offsetP, out, strideOut, offsetOut );
@@ -96,21 +95,22 @@ function ddiff( N, k, x, strideX, offsetX, N1, prepend, strideP, offsetP, N2, ap
 
 		return out;
 	}
+	// Compute the first forward difference:
+	base( N, x, strideX, offsetX, N1, prepend, strideP, offsetP, N2, append, strideA, offsetA, workspace, strideW, offsetW );
 
+	// If `k` is one, we're finished...
 	if ( k === 1 ) {
-		base( N, x, strideX, offsetX, N1, prepend, strideP, offsetP, N2, append, strideA, offsetA, out, strideOut, offsetOut );
 		return out;
 	}
-
-	base( N, x, strideX, offsetX, N1, prepend, strideP, offsetP, N2, append, strideA, offsetA, workspace, strideW, offsetW );
-
+	// Otherwise, recursively compute forward differences...
 	n = total - 1;
-	for ( i = 1; i < k - 1; i++ ) {
+	for ( i = 1; i < k-1; i++ ) {
 		base( n, workspace, strideW, offsetW, 0, prepend, strideP, offsetP, 0, append, strideA, offsetA, workspace, strideW, offsetW );
 		n -= 1;
 	}
-
+	// For the last forward difference, ensure that results are written to the output array:
 	base( n, workspace, strideW, offsetW, 0, prepend, strideP, offsetP, 0, append, strideA, offsetA, out, strideOut, offsetOut );
+
 	return out;
 }