diff --git a/du6/list_ops.c b/du6/list_ops.c
index 843e751..de72c4c 100644
--- a/du6/list_ops.c
+++ b/du6/list_ops.c
@@ -67,7 +67,7 @@ list_t *filter_list(list_t *list, bool (*filter)(list_element_t)) {
     size_t j = 0;
     for (size_t i = 0; i < list->length; i++) {
         if (filter(list->elements[i])) {
-            new->elements[j++] = list->elements[i];
+            new->elements[j+] = list->elements[i];
         }
     }
 
@@ -79,8 +79,9 @@ list_t *map_list(list_t *lst, list_element_t (*func)(list_element_t)) {
 
     size_t n = lst->length;
     list_t *mapped = malloc(sizeof(list_t) + n * sizeof(list_element_t));
-    if (mapped == NULL) return NULL;
-
+    if (mapped == NULL) {
+        return NULL;
+    }
     mapped->length = n;
 
     for (size_t i = 0; i < n; ++i) {
@@ -104,18 +105,7 @@ acc = folder(acc, lst->elements[i]);
 return acc;
 }
 
-list_element_t foldr_list(list_t *lst, list_element_t init,
-    list_element_t (*folder)(list_element_t, list_element_t)) {
-list_element_t acc = init;
 
-if (lst && folder) {
-for (size_t i = lst->length; i > 0; --i) {
-acc = folder(lst->elements[i - 1], acc);
-}
-}
-
-return acc;
-}
 
 list_t *reverse_list(list_t *lst) {
     if (!lst) return NULL;
@@ -124,7 +114,7 @@ list_t *reverse_list(list_t *lst) {
     list_t *reversed = malloc(sizeof(list_t) + n * sizeof(list_element_t));
     if (!reversed) return NULL;
 
-    
+    reversed->length = n;
 
     for (size_t i = 0; i < n; ++i) {
         reversed->elements[i] = lst->elements[n - i - 1];