Add iterators for a couple queues.

pq/lib.go

@@ -24,6 +24,7 @@
 package pq
 
 import (
+	"iter"
 	"sync"
 
 	"gogs.humancabbage.net/sam/priorityq"
@@ -153,3 +154,18 @@ func (s *state[P, T]) TrySend(priority P, value T) error {
 	s.canRecv.Broadcast()
 	return nil
 }
+
+// Iter returns an iterator that consumes values until the queue is closed.
+func (s *state[P, T]) Iter() iter.Seq[T] {
+	return func(yield func(T) bool) {
+		for {
+			_, t, ok := s.Recv()
+			if !ok {
+				return
+			}
+			if !yield(t) {
+				return
+			}
+		}
+	}
+}

pq/lib_test.go

@@ -147,6 +147,30 @@ func TestConcProducerConsumer(t *testing.T) {
 	wg.Wait()
 }
 
+func TestIter(t *testing.T) {
+	t.Parallel()
+	q := pq.Make[int, int](4)
+	q.Send(4, 0)
+	q.Send(3, 1)
+	q.Send(2, 2)
+	q.Send(1, 3)
+	q.Close()
+	i := 0
+	for v := range q.Iter() {
+		if v != i {
+			t.Errorf("expected %d, got %d", i, v)
+		}
+		i++
+	}
+
+	// to test yield() returning false
+	q = pq.Make[int, int](4)
+	q.Send(1, 3)
+	for _ = range q.Iter() {
+		break
+	}
+}
+
 func BenchmarkSend(b *testing.B) {
 	q := pq.Make[int, int](b.N)
 	// randomize priorities to get amortized cost per op