Updating error states and example program

Author: dluman

examples/.pcconfig

@@ -1,3 +1,3 @@
 storage:
     stack_size: 18
-    stack_base: 80
+    stack_base: 50

examples/stack.ppc

@@ -8,6 +8,8 @@
 8   903     @ Push new value to stack
 9   905     @ Get the stack pointer value
 10  902     @ Output the value
-11  906     @ Calculate the stack height
-12  902     @ Output the value
-13  000     @ Halt
+11  904     @ Pop the last value off the stack
+12  902     @ Print that value
+13  906     @ Calculate the stack height
+14  902     @ Output the value
+15  000     @ Halt

src/paperpc/cmd.py

@@ -155,15 +155,23 @@ def __push(self, acc, storage):
         if storage.stack_ptr - storage.stack_base > storage.stack_size:
             print("[ERROR] Stack overflow!")
             sys.exit(1)
-        storage._spaces[storage.stack_ptr] = acc.value
+        try:
+            storage._spaces[storage.stack_ptr] = acc.value
+        except IndexError:
+            print(f"[ERROR] Stack pointer set beyond storage limit!")
+            sys.exit(1)
 
     @storage
     def __pop(self, acc, storage):
         stack_len = len(storage.stack)
         stack_pos = storage.stack_base + stack_len
         storage._spaces[storage.stack_ptr] = "---"
-        acc.value = int(storage.stack.pop())
-        storage.stack_ptr -= 1
+        try:
+            acc.value = int(storage.stack.pop())
+            storage.stack_ptr -= 1
+        except IndexError:
+            print(f"[ERROR] Stack pointer set beyond storage limit!")
+            sys.exit(1)
 
     @storage
     def __ptr(self, acc, storage):