Example iterators (#114)

* Fixed #90

* Added an example for SliceIterator

api_matop.go

@@ -1,6 +1,8 @@
 package tensor
 
-import "github.com/pkg/errors"
+import (
+	"github.com/pkg/errors"
+)
 
 // this file handles matops. While by default most of these matops should already have been defined as part of the
 // Tensor interface, not all are possible(for example, concatenating a sparse tensor), hence the need for the following functions

example_iterator_test.go

@@ -1,52 +1,77 @@
-package tensor
-
-import "fmt"
-
-// This is an example of how to use `IteratorFromDense` from a row-major Dense tensor
-func Example_iteratorRowmajor() {
-	T := New(WithShape(2, 3), WithBacking([]float64{0, 1, 2, 3, 4, 5}))
-	it := IteratorFromDense(T)
-	fmt.Printf("T:\n%v\n", T)
-
-	for i, err := it.Start(); err == nil; i, err = it.Next() {
-		fmt.Printf("i: %d, coord: %v\n", i, it.Coord())
-	}
-
-	// Output:
-	// T:
-	// ⎡0  1  2⎤
-	// ⎣3  4  5⎦
-	//
-	// i: 0, coord: [0 1]
-	// i: 1, coord: [0 2]
-	// i: 2, coord: [1 0]
-	// i: 3, coord: [1 1]
-	// i: 4, coord: [1 2]
-	// i: 5, coord: [0 0]
-
-}
-
-// This is an example of using `IteratorFromDense` on a col-major Dense tensor. More importantly
-// this example shows the order of the iteration.
-func Example_iteratorcolMajor() {
-	T := New(WithShape(2, 3), WithBacking([]float64{0, 1, 2, 3, 4, 5}), AsFortran(nil))
-	it := IteratorFromDense(T)
-	fmt.Printf("T:\n%v\n", T)
-
-	for i, err := it.Start(); err == nil; i, err = it.Next() {
-		fmt.Printf("i: %d, coord: %v\n", i, it.Coord())
-	}
-
-	// Output:
-	// T:
-	// ⎡0  2  4⎤
-	// ⎣1  3  5⎦
-	//
-	// i: 0, coord: [0 1]
-	// i: 2, coord: [0 2]
-	// i: 4, coord: [1 0]
-	// i: 1, coord: [1 1]
-	// i: 3, coord: [1 2]
-	// i: 5, coord: [0 0]
-
-}
+package tensor
+
+import "fmt"
+
+// This is an example of how to use `IteratorFromDense` from a row-major Dense tensor
+func Example_iteratorRowmajor() {
+	T := New(WithShape(2, 3), WithBacking([]float64{0, 1, 2, 3, 4, 5}))
+	it := IteratorFromDense(T)
+	fmt.Printf("T:\n%v\n", T)
+
+	for i, err := it.Start(); err == nil; i, err = it.Next() {
+		fmt.Printf("i: %d, coord: %v\n", i, it.Coord())
+	}
+
+	// Output:
+	// T:
+	// ⎡0  1  2⎤
+	// ⎣3  4  5⎦
+	//
+	// i: 0, coord: [0 1]
+	// i: 1, coord: [0 2]
+	// i: 2, coord: [1 0]
+	// i: 3, coord: [1 1]
+	// i: 4, coord: [1 2]
+	// i: 5, coord: [0 0]
+
+}
+
+// This is an example of using `IteratorFromDense` on a col-major Dense tensor. More importantly
+// this example shows the order of the iteration.
+func Example_iteratorcolMajor() {
+	T := New(WithShape(2, 3), WithBacking([]float64{0, 1, 2, 3, 4, 5}), AsFortran(nil))
+	it := IteratorFromDense(T)
+	fmt.Printf("T:\n%v\n", T)
+
+	for i, err := it.Start(); err == nil; i, err = it.Next() {
+		fmt.Printf("i: %d, coord: %v\n", i, it.Coord())
+	}
+
+	// Output:
+	// T:
+	// ⎡0  2  4⎤
+	// ⎣1  3  5⎦
+	//
+	// i: 0, coord: [0 1]
+	// i: 2, coord: [0 2]
+	// i: 4, coord: [1 0]
+	// i: 1, coord: [1 1]
+	// i: 3, coord: [1 2]
+	// i: 5, coord: [0 0]
+
+}
+
+func ExampleSliceIter() {
+	T := New(WithShape(3, 3), WithBacking(Range(Float64, 0, 9)))
+	S, err := T.Slice(makeRS(1, 3), makeRS(1, 3))
+	if err != nil {
+		fmt.Printf("Err %v\n", err)
+		return
+	}
+	fmt.Printf("S (requires iterator? %t)\n%v\n", S.(*Dense).RequiresIterator(), S)
+	it := IteratorFromDense(S.(*Dense))
+	for i, err := it.Start(); err == nil; i, err = it.Next() {
+		fmt.Printf("i %d, coord %v\n", i, it.Coord())
+	}
+
+	// Output:
+	// S (requires iterator? true)
+	// ⎡4  5⎤
+	// ⎣7  8⎦
+	//
+	// i 0, coord [0 1]
+	// i 1, coord [1 0]
+	// i 3, coord [1 1]
+	// i 4, coord [0 0]
+
+}