diff --git a/du6/list_ops.c b/du6/list_ops.c
index af74029..209143a 100644
--- a/du6/list_ops.c
+++ b/du6/list_ops.c
@@ -1,49 +1,102 @@
 #include "list_ops.h"
-#include <string.h> 
+#include <string.h>
 
 list_t *new_list(size_t length, list_element_t elements[]) {
     list_t *list = malloc(sizeof(list_t) + sizeof(list_element_t) * length);
     if (!list) return NULL;
-
     list->length = length;
-    if (elements && length > 0) {
+    if (length && elements)
         memcpy(list->elements, elements, sizeof(list_element_t) * length);
-    }
     return list;
 }
-list_t *append_list(list_t *list1, list_t *list2) {
-    size_t len1 = list1 ? list1->length : 0;
-    size_t len2 = list2 ? list2->length : 0;
 
-    list_t *result = malloc(sizeof(list_t) + sizeof(list_element_t) * (len1 + len2));
-    if (!result) return NULL;
-
-    result->length = len1 + len2;
-    if (len1 > 0)
-        memcpy(result->elements, list1->elements, sizeof(list_element_t) * len1);
-    if (len2 > 0)
-        memcpy(result->elements + len1, list2->elements, sizeof(list_element_t) * len2);
-
-    return result;
+void delete_list(list_t *list) {
+    free(list);
 }
+
+list_t *append_list(list_t *list1, list_t *list2) {
+    size_t new_length = list1->length + list2->length;
+    list_t *new_list_ptr = malloc(sizeof(list_t) + sizeof(list_element_t) * new_length);
+    if (!new_list_ptr) return NULL;
+
+    new_list_ptr->length = new_length;
+
+    for (size_t i = 0; i < list1->length; i++) {
+        new_list_ptr->elements[i] = list1->elements[i];
+    }
+    for (size_t i = 0; i < list2->length; i++) {
+        new_list_ptr->elements[list1->length + i] = list2->elements[i];
+    }
+
+    return new_list_ptr;
+}
+
 list_t *filter_list(list_t *list, bool (*filter)(list_element_t)) {
-    if (!list || list->length == 0) return new_list(0, NULL);
-
-    list_element_t *temp = malloc(sizeof(list_element_t) * list->length);
-    if (!temp) return NULL;
-
     size_t count = 0;
-    for (size_t i = 0; i < list->length; ++i) {
+
+    for (size_t i = 0; i < list->length; i++) {
+        if (filter(list->elements[i])) count++;
+    }
+
+    list_t *new_list_ptr = malloc(sizeof(list_t) + sizeof(list_element_t) * count);
+    if (!new_list_ptr) return NULL;
+
+    new_list_ptr->length = count;
+
+    size_t index = 0;
+    for (size_t i = 0; i < list->length; i++) {
         if (filter(list->elements[i])) {
-            temp[count++] = list->elements[i];
+            new_list_ptr->elements[index++] = list->elements[i];
         }
     }
 
-    list_t *result = new_list(count, temp);
-    free(temp);
-    return result;
+    return new_list_ptr;
 }
 
 size_t length_list(list_t *list) {
-    return list ? list->length : 0;
-}
\ No newline at end of file
+    return list->length;
+}
+
+list_t *map_list(list_t *list, list_element_t (*map)(list_element_t)) {
+    list_t *new_list_ptr = malloc(sizeof(list_t) + sizeof(list_element_t) * list->length);
+    if (!new_list_ptr) return NULL;
+
+    new_list_ptr->length = list->length;
+
+    for (size_t i = 0; i < list->length; i++) {
+        new_list_ptr->elements[i] = map(list->elements[i]);
+    }
+
+    return new_list_ptr;
+}
+
+list_element_t foldl_list(list_t *list, list_element_t initial,
+                          list_element_t (*foldl)(list_element_t, list_element_t)) {
+    list_element_t result = initial;
+    for (size_t i = 0; i < list->length; i++) {
+        result = foldl(result, list->elements[i]);
+    }
+    return result;
+}
+
+list_element_t foldr_list(list_t *list, list_element_t initial,
+                          list_element_t (*foldr)(list_element_t, list_element_t)) {
+    list_element_t result = initial;
+    for (ssize_t i = list->length - 1; i >= 0; i--) {
+        result = foldr(list->elements[i], result);
+    }
+    return result;
+}
+
+list_t *reverse_list(list_t *list) {
+    list_t *new_list_ptr = malloc(sizeof(list_t) + sizeof(list_element_t) * list->length);
+    if (!new_list_ptr) return NULL;
+
+    new_list_ptr->length = list->length;
+
+    for (size_t i = 0; i < list->length; i++) {
+        new_list_ptr->elements[i] = list->elements[list->length - i - 1];
+    }
+
+    return new_list_ptr;
+}