Add Queue container

Author: tomas-novotny

container/queue/queue.go

@@ -0,0 +1,56 @@
+package queue
+
+// Queue is generic FIFO queue.
+type Queue[E any] struct {
+	s []E
+}
+
+// New creates a new queue backed by a slice.
+func New[E any]() *Queue[E] {
+	return &Queue[E]{}
+}
+
+// Push adds an element to last position of the queue.
+func (q *Queue[E]) Push(e E) {
+	q.s = append(q.s, e)
+}
+
+// Pop removes and returns the first element from the queue.
+// Pop panics if the queue is empty.
+func (q *Queue[E]) Pop() E {
+	current := q.s[0]
+
+	var zero E
+	q.s[0] = zero
+	q.s = q.s[1:]
+
+	return current
+}
+
+// Peek returns the first element in the queue.
+// Peek panics if the queue is empty.
+func (q *Queue[E]) Peek() E {
+	return q.s[0]
+}
+
+// Len returns the number of elements in the queue.
+func (q *Queue[E]) Len() int {
+	return len(q.s)
+}
+
+// Empty returns true if the queue is empty.
+func (q *Queue[E]) Empty() bool {
+	return len(q.s) == 0
+}
+
+// Clear removes all elements from the queue.
+func (q *Queue[E]) Clear() {
+	clear(q.s)
+	q.s = q.s[:0]
+}
+
+// Slice returns the underlying slice.
+// The queue retains the returned slice, so altering the slice may break the invariants and invalidate the queue.
+func (q *Queue[E]) Slice() []E {
+	return q.s
+}

container/queue/queue_test.go

@@ -0,0 +1,35 @@
+package queue
+
+import (
+	"testing"
+
+	"github.com/gravitton/assert"
+)
+
+func TestQueue(t *testing.T) {
+	q := New[int]()
+
+	assert.Equal(t, q.Len(), 0)
+	assert.True(t, q.Empty())
+
+	q.Push(2)
+	q.Push(3)
+	q.Push(1)
+
+	assert.Equal(t, q.Len(), 3)
+	assert.False(t, q.Empty())
+
+	assert.Equal(t, q.Peek(), 2)
+	assert.Equal(t, q.Len(), 3)
+
+	assert.Equal(t, q.Pop(), 2)
+	assert.Equal(t, q.Len(), 2)
+
+	s := q.Slice()
+	assert.Equal(t, s, []int{3, 1})
+	q.Clear()
+
+	assert.Equal(t, s, []int{0, 0})
+	assert.Equal(t, q.Len(), 0)
+	assert.True(t, q.Empty())
+}