implement a PositionStack

1 files changed, 23 insertions, 0 deletions

diff --git a/stack.c b/stack.c
new file mode 100644
index 0000000..bcdfbd3
--- /dev/null
+++ b/stack.c
@@ -0,0 +1,23 @@
+#include "stack.h"
+#include "structs.h"
+
+PositionStack ps_new(void) {
+    PositionStack ps;
+    ps.top = 0;
+    return ps;
+}
+
+int ps_push(PositionStack ps, Position pos) {
+    ps.arr[ps.top] = pos;
+    ps.top += 1;
+}
+
+Position ps_pop(PositionStack ps) {
+    ps.top -= 1;
+    return ps.arr[ps.top];
+}
+
+Position ps_peek(PositionStack ps) {
+    return ps.arr[ps.top - 1];
+}
+