Add .Chain for iterator method chaining

Author: BooleanCat

iter/chain_test.go

@@ -14,6 +14,11 @@ func ExampleChain() {
 	// Output: [1 2 3 4 0 9]
 }
 
+func ExampleChain_method() {
+	fmt.Println(iter.Lift([]int{1, 2}).Chain(iter.Lift([]int{3, 4}), iter.Lift([]int{0, 9})).Collect())
+	// Output: [1 2 3 4 0 9]
+}
+
 func TestChainMultiple(t *testing.T) {
 	items := iter.Chain[int](iter.Lift([]int{1, 2}), iter.Lift([]int{3, 4}))
 	assert.Equal(t, items.Next().Unwrap(), 1)

iter/filter_test.go

@@ -23,6 +23,18 @@ func ExampleFilter() {
 	// None
 }
 
+func ExampleFilter_method() {
+	filtered := iter.Lift([]int{0, 1, 0, 2}).Filter(filters.IsZero[int])
+	fmt.Println(filtered.Next())
+	fmt.Println(filtered.Next())
+	fmt.Println(filtered.Next())
+
+	// Output:
+	// Some(0)
+	// Some(0)
+	// None
+}
+
 func ExampleFilterMap() {
 	selectAndTripleOdds := func(x int) option.Option[int] {
 		if x%2 == 0 {

iter/iter.go

@@ -127,3 +127,9 @@ func (iter *BaseIter[T]) Take(n uint) *TakeIter[T] {
 func (iter *BaseIter[T]) Filter(fun func(T) bool) *FilterIter[T] {
 	return Filter[T](iter, fun)
 }
+
+// Chain is a convenience method for [Chain], providing this iterator as an
+// argument.
+func (iter *BaseIter[T]) Chain(iterators ...Iterator[T]) *ChainIter[T] {
+	return Chain[T](append([]Iterator[T]{iter}, iterators...)...)
+}

iter/iter_test.go

@@ -185,3 +185,8 @@ func TestBaseIteratorFilter(t *testing.T) {
 	items := iter.Lift([]int{1, 2, 3}).Filter(filters.IsEven[int]).Collect()
 	assert.SliceEqual(t, items, []int{2})
 }
+
+func TestBaseIteratorChain(t *testing.T) {
+	numbers := iter.Lift([]int{1, 2}).Chain(iter.Lift([]int{3, 4})).Collect()
+	assert.SliceEqual[int](t, numbers, []int{1, 2, 3, 4})
+}