1 files changed, 8 insertions, 6 deletions
diff --git a/stack.c b/stack.c
index bcdfbd3..cf169c5 100644
--- a/stack.c
+++ b/stack.c
@@ -7,14 +7,16 @@ PositionStack ps_new(void) {
     return ps;
 }
 
-int ps_push(PositionStack ps, Position pos) {
-    ps.arr[ps.top] = pos;
-    ps.top += 1;
+int ps_push(PositionStack *ps, Position pos) {
+    //TODO: check for stack overflow
+    ps->arr[ps->top] = pos;
+    ps->top += 1;
+    return 0;
 }
 
-Position ps_pop(PositionStack ps) {
-    ps.top -= 1;
-    return ps.arr[ps.top];
+Position ps_pop(PositionStack *ps) {
+    ps->top -= 1;
+    return ps->arr[ps->top];
 }
 
 Position ps_peek(PositionStack ps) {