From 4167860e015a779f83a17bc8754c7070bdfba336 Mon Sep 17 00:00:00 2001
From: sanine <sanine.not@pm.me>
Date: Fri, 24 Oct 2025 13:40:15 -0500
Subject: add list prepend

---
 lichen.c      | 22 +++++++++++++++++---
 lichen.h      |  1 +
 lichen.test.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 86 insertions(+), 3 deletions(-)

diff --git a/lichen.c b/lichen.c
index f028d92..b0b0684 100644
--- a/lichen.c
+++ b/lichen.c
@@ -79,10 +79,10 @@ void li_free_ll(struct li_ll_t *list, void (*free_data)(void*)) {
 
 void li_ll_append(struct li_ll_t *list, void *data) {
   li_llnode_t *n = li_alloc_llnode();
-  n->data = data;
   if (n == NULL) {
     return;
   }
+  n->data = data;
   if (list->end != NULL) {
     list->end->next = n;
     list->end = n;
@@ -93,9 +93,25 @@ void li_ll_append(struct li_ll_t *list, void *data) {
   list->count += 1;
 }
 
+
+void li_ll_prepend(struct li_ll_t *list, void *data) {
+  li_llnode_t *n = li_alloc_llnode();
+  if (n == NULL) {
+    return;
+  }
+  n->data = data;
+  if (list->head != NULL) {
+    n->next = list->head;
+    list->head = n;
+  } else {
+    list->head = n;
+    list->end = n;
+  }
+  list->count += 1;
+}
+
+
 struct li_ll_t * li_copy_list(struct li_ll_t *list) {
   list = list;
   return NULL;
 }
-
-
diff --git a/lichen.h b/lichen.h
index a607d24..4bcd608 100644
--- a/lichen.h
+++ b/lichen.h
@@ -50,6 +50,7 @@ struct li_ll_t * li_alloc_ll();
 // free a linked list
 void li_free_ll(struct li_ll_t *list, void (*free_data)(void*));
 void li_ll_append(struct li_ll_t *list, void *data);
+void li_ll_prepend(struct li_ll_t *list, void *data);
 struct li_ll_t * li_copy_list(struct li_ll_t *list);
 
 
diff --git a/lichen.test.c b/lichen.test.c
index bca7d27..622f480 100644
--- a/lichen.test.c
+++ b/lichen.test.c
@@ -81,6 +81,72 @@ LILY_TEST("append to list") {
 #include LILY_PUSH_TEST()
 
 
+LILY_TEST("prepend to list") {
+  struct li_ll_t *list = li_alloc_ll();
+  REQUIRE_NEQ(list, NULL, "%p");
+
+  int a = 1; int b = 2; int c = 3;
+
+  li_ll_prepend(list, &b);
+  CHECK_EQ(list->count, 1, "%d");
+  REQUIRE_NEQ(list->head, NULL, "%p");
+  CHECK_EQ(list->head->data, &b, "%p");
+  CHECK_EQ(list->head->next, NULL, "%p");
+
+  li_ll_prepend(list, &a);
+  CHECK_EQ(list->count, 2, "%d");
+  REQUIRE_NEQ(list->head->next, NULL, "%p");
+  CHECK_EQ(list->head->data, &a, "%p");
+  CHECK_EQ(list->head->next->data, &b, "%p");
+  CHECK_EQ(list->head->next->next, NULL, "%p");
+
+  li_ll_prepend(list, &c);
+  CHECK_EQ(list->count, 3, "%d");
+  REQUIRE_NEQ(list->head->next->next, NULL, "%p");
+  CHECK_EQ(list->head->data, &c, "%p");
+  CHECK_EQ(list->head->next->data, &a, "%p");
+  CHECK_EQ(list->head->next->next->data, &b, "%p");
+  CHECK_EQ(list->head->next->next->next, NULL, "%p");
+
+  li_free_ll(list, do_nothing);
+}
+#include LILY_PUSH_TEST()
+
+
+LILY_TEST("mix prepends and appends") {
+  struct li_ll_t *list = li_alloc_ll();
+  REQUIRE_NEQ(list, NULL, "%p");
+
+  int a = 1; int b = 2; int c = 3;
+
+  li_ll_prepend(list, &b);
+  CHECK_EQ(list->count, 1, "%d");
+  REQUIRE_NEQ(list->head, NULL, "%p");
+  CHECK_EQ(list->head->data, &b, "%p");
+  CHECK_EQ(list->head->next, NULL, "%p");
+
+  li_ll_prepend(list, &a);
+  CHECK_EQ(list->count, 2, "%d");
+  REQUIRE_NEQ(list->head->next, NULL, "%p");
+  CHECK_EQ(list->head->data, &a, "%p");
+  CHECK_EQ(list->head->next->data, &b, "%p");
+  CHECK_EQ(list->head->next->next, NULL, "%p");
+
+  li_ll_append(list, &c);
+  CHECK_EQ(list->count, 3, "%d");
+  REQUIRE_NEQ(list->head->next->next, NULL, "%p");
+  CHECK_EQ(list->head->data, &a, "%p");
+  CHECK_EQ(list->head->next->data, &b, "%p");
+  CHECK_EQ(list->head->next->next->data, &c, "%p");
+  CHECK_EQ(list->head->next->next->next, NULL, "%p");
+
+  li_free_ll(list, do_nothing);
+
+}
+#include LILY_PUSH_TEST()
+
+
+
 #define LILY_FILE_END
 #include LILY_REGISTER_TESTS()
 
-- 
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