Add Copies iterator returning copies of a specified object

iters/valit/copies.go

@@ -0,0 +1,37 @@
+// Copyright (c) 2022 individual contributors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// <https://www.apache.org/licenses/LICENSE-2.0>
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package valit
+
+import (
+	"github.com/0x5a17ed/itkit"
+)
+
+// Copier represents a struct that can copy itself.
+type Copier[T any] interface {
+	Copy() T
+}
+
+// CopyIterator represents an iterator yielding copies of a given
+// value on every iteration of the iterator.
+type CopyIterator[T Copier[T]] struct{ src, cur T }
+
+func (it CopyIterator[T]) Value() T   { return it.cur }
+func (it CopyIterator[T]) Next() bool { it.cur = it.src.Copy(); return true }
+
+// Copies provides an iterator which yields copies of a given value on
+// every iteration of the iterator.
+func Copies[T Copier[T]](v T) itkit.Iterator[T] {
+	return &CopyIterator[T]{src: v}
+}

iters/valit/copies_test.go

@@ -0,0 +1,44 @@
+// Copyright (c) 2022 individual contributors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// <https://www.apache.org/licenses/LICENSE-2.0>
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package valit_test
+
+import (
+	"testing"
+
+	assertPkg "github.com/stretchr/testify/assert"
+	requirePkg "github.com/stretchr/testify/require"
+
+	"github.com/0x5a17ed/itkit/iters/valit"
+)
+
+type object struct{ copies int }
+
+func (t *object) Copy() *object {
+	t.copies++
+	return &object{}
+}
+
+func TestCopies(t *testing.T) {
+	var o object
+	iter := valit.Copies(&o)
+
+	for i := 0; i < 10; i++ {
+		requirePkg.True(t, iter.Next())
+		assertPkg.NotSame(t, &o, iter.Value())
+		assertPkg.Same(t, iter.Value(), iter.Value())
+	}
+
+	assertPkg.Equal(t, 10, o.copies)
+}

iters/valit/docs.go

@@ -16,5 +16,6 @@
 // iterators.
 //
 // Iterators:
+//   - Copies - yields copies of a given value forever.
 //   - Fill - yields the same value forever.
 package valit