Grundlegende Stack-funktionen implementiert und Struct nochmal ueberarbeitet

stack.c

@@ -16,9 +16,9 @@ StackNode *push(StackNode *stack, void *data)
         {
         return NULL; //Speicherfehler
         }
-      t->prev = stack;
+      t->next = stack;
       t->data = data;
-      return t;
+      return t; //Gibt den ersten StackNode des Stacks zurueck
       }
     return NULL;
 }
@@ -27,17 +27,32 @@ StackNode *push(StackNode *stack, void *data)
 // freed by caller.)
 StackNode *pop(StackNode *stack)
 {
-
+    if(stack)
+      {
+          StackNode *t = stack->next; //Naechstes Element im Stack wird erstes Element
+          free(stack);
+          return t;
+      }
 }
 
 // Returns the data of the top element.
 void *top(StackNode *stack)
 {
-
+    if(stack)
+      {
+      return stack->data;
+      }
+    return NULL;
 }
 
 // Clears stack and releases all memory.
 void clearStack(StackNode *stack)
 {
-
+  while(stack)
+  {
+      StackNode *tmp = stack;
+      stack = stack->prev;
+      free(tmp->data);
+      free(tmp);
+  }
 }

stack.h

@@ -10,7 +10,7 @@ The latest element is taken from the stack. */
 //TODO: passenden Datentyp als struct anlegen
 typedef{
   int* data;
-  struct StackNode *prev;
+  struct StackNode *next;
   }StackNode;
 
 // Pushes data as pointer onto the stack.