Initial Commit

ee_stack.h

@@ -0,0 +1,39 @@
+struct EE_STACK_NODE {
+    double datum;
+    struct EE_STACK_NODE* tail;
+};
+typedef struct EE_STACK_NODE NODE;
+typedef struct EE_STACK_NODE* STACK;
+
+STACK
+push(double datum, STACK tail){
+    /* Given a double value (datum), and a STACK (tail),
+     * push(datum,tail) is the STACK resulting from
+     * prepending datum to the STACK tail.
+     */
+     NODE* new_node = (NODE*)malloc(sizeof(NODE));
+        (*new_node).datum = datum;
+        (*new_node).tail  = tail;
+    return new_node;
+}
+
+STACK
+pop(STACK target_stack){
+    /* Given a STACK (target_stack), pop(target_stack)
+     * is the STACK resulting from the removal of the first
+     * item in target_stack;
+     */
+     if (target_stack == NULL){ return target_stack; }
+     STACK tail = (*target_stack).tail;
+     free(target_stack);
+     return tail;
+}
+
+double
+peek(STACK target_stack){
+    /* Given a STACK (target_stack), peek(STACK)
+     * is the first element's datum.
+     */
+     if (target_stack == NULL){ return 0; }
+     return (*target_stack).datum;
+}