Add iterators for a couple queues.

queue/lib.go

@@ -6,6 +6,8 @@
 // makes determining whether the queue is full or empty trivial.
 package queue
 
+import "iter"
+
 // Q is a non-concurrent queue.
 type Q[T any] struct {
 	buf  []T
@@ -73,3 +75,32 @@ func (b *Q[T]) PushBack(value T) {
 		b.tail = 0
 	}
 }
+
+// Iter returns an iterator over all items in the queue.
+//
+// This does not pop items off the queue.
+func (b *Q[T]) Iter() iter.Seq[T] {
+	return func(yield func(T) bool) {
+		remaining := b.len
+		i := b.head
+		for remaining > 0 {
+			yield(b.buf[i])
+			remaining--
+			i++
+			if i == b.len {
+				i = 0
+			}
+		}
+	}
+}
+
+// IterPop returns an iterator that pops each item off the queue.
+func (b *Q[T]) IterPop() iter.Seq[T] {
+	return func(yield func(T) bool) {
+		for b.CanPop() {
+			if !yield(b.PopFront()) {
+				break
+			}
+		}
+	}
+}

queue/lib_test.go

@@ -73,6 +73,51 @@ func TestFullPushPanic(t *testing.T) {
 	q.PushBack(2)
 }
 
+func TestIter(t *testing.T) {
+	q := queue.Make[int](4)
+	q.PushBack(1)
+	q.PushBack(2)
+	q.PushBack(3)
+	q.PushBack(4)
+	i := 0
+	for v := range q.Iter() {
+		expected := i + 1
+		if v != expected {
+			t.Errorf("iter %d should have value %d, not %d",
+				i, expected, v)
+		}
+		i++
+	}
+	if q.Len() != 4 {
+		t.Errorf("wrong length")
+	}
+}
+
+func TestIterPop(t *testing.T) {
+	t.Parallel()
+	q := queue.Make[int](4)
+	q.PushBack(1)
+	q.PushBack(2)
+	q.PushBack(3)
+	q.PushBack(4)
+	i := 0
+	for v := range q.IterPop() {
+		expected := i + 1
+		if v != expected {
+			t.Errorf("iter %d should have value %d, not %d",
+				i, expected, v)
+		}
+		i++
+		// to test yield() returning false
+		if i == 4 {
+			break
+		}
+	}
+	if q.Len() != 0 {
+		t.Errorf("wrong length")
+	}
+}
+
 func BenchmarkPush(b *testing.B) {
 	q := queue.Make[int](b.N)
 	rs := rand.NewSource(0)