From d0c11c89d069a86baffff7da027bdd9f0b63d393 Mon Sep 17 00:00:00 2001
From: chewxy <chewxy@gmail.com>
Date: Wed, 4 May 2022 14:21:29 +1000
Subject: [PATCH] Added examples for SliceInto

---
 dense_matop.go              |  6 ++--
 example_dense_matop_test.go | 65 +++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/dense_matop.go b/dense_matop.go
index 3a04f9c..3a9f005 100644
--- a/dense_matop.go
+++ b/dense_matop.go
@@ -246,8 +246,10 @@ func (t *Dense) Slice(slices ...Slice) (retVal View, err error) {
 // SliceInto is a convenience method. It does NOT copy the values - it simply updates the AP of the view.
 // The underlying data is the same.
 // This method will override ALL the metadata in view.
-func (t *Dense) SliceInto(view Tensor, slices ...Slice) (retVal View, err error) {
+func (t *Dense) SliceInto(view Tensor, slices ...Slice) (retVal Tensor, err error) {
 	switch view := view.(type) {
+	case nil:
+		return t.Slice(slices...)
 	case DenseView:
 		v := view.Dense
 		if v, err = t.sliceIntoDense(v, slices...); err != nil {
@@ -261,7 +263,7 @@ func (t *Dense) SliceInto(view Tensor, slices ...Slice) (retVal View, err error)
 		}
 		return DenseView{view}, nil
 	default:
-		return nil, nyierr(typeNYI)
+		return nil, nyierr(typeNYI, view)
 	}
 }
 
diff --git a/example_dense_matop_test.go b/example_dense_matop_test.go
index 1e81271..c6f50a5 100644
--- a/example_dense_matop_test.go
+++ b/example_dense_matop_test.go
@@ -31,6 +31,71 @@ func ExampleDense_Slice() {
 	// [1  4]
 }
 
+func ExampleDense_SliceInto() {
+	var v Tensor
+	var err error
+	T := New(WithBacking(Range(Int, 0, 9)), WithShape(3, 3))
+	fmt.Println("SliceInto works with nil values. It simply creates a View.\n==========================================================")
+	fmt.Printf("T:\n%v\n", T)
+
+	if v, err = T.SliceInto(v, makeRS(0, 2), makeRS(0, 2)); err != nil {
+		fmt.Printf("ERR %v\n", err)
+		return
+	}
+	fmt.Printf("T[0:2, 0:2]:\n%v\n", v)
+
+	v.Zero()
+	fmt.Printf("When v is zeroed, T is zeroed too.\n==================================\nv:\n%v\nT:\n%v\n", v, T)
+
+	fmt.Println("Primary use case of SliceInto.\n==============================")
+	T = New(WithBacking(Range(Int, 0, 9)), WithShape(3, 3))
+	fmt.Printf("T:\n%v\nv:\n%v\n", T, v)
+	if v, err = T.SliceInto(v, makeRS(0, 2), makeRS(0, 2)); err != nil {
+		fmt.Printf("ERR %v\n", err)
+		return
+	}
+	fmt.Printf("v = T[0:2, 0:2]:\n%v\n", v)
+
+	// Output:
+	// SliceInto works with nil values. It simply creates a View.
+	// ==========================================================
+	// T:
+	// ⎡0  1  2⎤
+	// ⎢3  4  5⎥
+	// ⎣6  7  8⎦
+	//
+	// T[0:2, 0:2]:
+	// ⎡0  1⎤
+	// ⎣3  4⎦
+	//
+	// When v is zeroed, T is zeroed too.
+	// ==================================
+	// v:
+	// ⎡0  0⎤
+	// ⎣0  0⎦
+	//
+	// T:
+	// ⎡0  0  0⎤
+	// ⎢0  0  5⎥
+	// ⎣6  7  8⎦
+	//
+	// Primary use case of SliceInto.
+	// ==============================
+	// T:
+	// ⎡0  1  2⎤
+	// ⎢3  4  5⎥
+	// ⎣6  7  8⎦
+	//
+	// v:
+	// ⎡0  0⎤
+	// ⎣0  0⎦
+	//
+	// v = T[0:2, 0:2]:
+	// ⎡0  1⎤
+	// ⎣3  4⎦
+
+}
+
 // Slicing works on one dimensional arrays too:
 func ExampleDense_Slice_oneDimension() {
 	var T Tensor