From 0e8838b64000a59463ae817488b1ebae9828b55c Mon Sep 17 00:00:00 2001
From: sbosse <sbosse@uni-bremen.de>
Date: Mon, 16 Mar 2026 11:10:14 +0100
Subject: [PATCH] Mon 16 Mar 11:09:06 CET 2026

---
 src/stack.h | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 src/stack.h

diff --git a/src/stack.h b/src/stack.h
new file mode 100644
index 0000000..d2e5a56
--- /dev/null
+++ b/src/stack.h
@@ -0,0 +1,34 @@
+#ifndef _STACK_H
+#define _STACK_H
+#include "types.h"
+
+typedef struct {
+  number_t *data;
+  index_t  size;
+  index_t  sp;
+} stack_t;
+
+
+/*
+  Check for possible stack underflow (should normally not happen, in contrast to stack overflow)
+*/
+#if STACKUNDERFLOWCHECK>0 
+#define STACKUNDERFLOW(DS,N,R) if (SEMPTYN(DS,N)) { R->error=ESTACK; return 0; };
+#else
+#define STACKUNDERFLOW(DS,N,R)
+#endif
+
+#define SEMPTY(S)     S->sp==0
+#define SFULL(S)      S->sp==S->size
+#define SEMPTYN(S,n)  S->sp<n
+#define SFULLN(S,n)  (S->sp+n)>S->size
+#define POP(S)        S->data[--S->sp]
+#define PUSH(S,x)     S->data[S->sp++]=x
+#define NTH(S,n)      S->data[S->sp-n]
+
+stack_t * StackAllocate(int size);
+void StackCopy(stack_t *src, stack_t *dst);
+void StackInit(stack_t *S,int size,number_t *data);
+void StackReset(stack_t *S);
+
+#endif