--- a/queue.c	Sat Jun 24 23:33:16 2017 +0800
+++ b/queue.c	Fri Feb 09 23:49:22 2018 +0800
@@ -33,7 +33,7 @@
 	queue->count = 0;
 }
 
-int isempty(struct Queue* queue) {
+int isempty(const struct Queue* queue) {
 
 	return (queue->head == NULL);
 }
@@ -60,7 +60,7 @@
 	return ret;
 }
 
-void *examine(struct Queue* queue) {
+void *examine(const struct Queue* queue) {
 
 	dropbear_assert(!isempty(queue));
 	return queue->head->item;