claudio did the list

list.c

@@ -0,0 +1,125 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#define TYPE int
+//A list is one of:
+// - (make-note element next)
+// - '() -> NULL
+
+struct node {
+    TYPE element;
+    struct node* prev;
+    struct node* next;
+};
+
+typedef struct node node_t;
+
+typedef struct {
+    node* first;
+} list_t;
+
+size_t list_length(const list_t* self) {
+    size_t length = 0;
+    node_t* i = self->first;
+
+    while (i != NULL) {
+        length++;
+        i = self->next;
+    }
+
+    return length;
+}
+
+node_t* list_ith(const list_t* self, const size_t position) {
+    size_t found;
+    node_t* elem = list_ith_or_last(self, position, &found);
+    return found != position ? NULL : elem;
+}
+
+node_t* list_ith_or_last(const list_t* self, const size_t position,
+    const size_t* returned) {
+    node_t* to_reach = self->first;
+    size_t i;
+    for (i = 0; i < position && to_reach->next != NULL; i++) {
+        to_reach = to_reach->next;
+    }
+    *returned = i;
+    return to_reach;
+}
+
+node_t* make_node(TYPE element) {
+    node_t* node = malloc(sizeof(node));
+    node->element = element;
+    node->next = NULL;
+    node->prev = NULL;
+}
+
+void free_list(const list_t* list) {
+    while(list->first != NULL) {
+        free(list_remove(self, 0));
+    }
+}
+
+size_t list_copy_slice(const list_t* self, const list_t* destination,
+    const size_t from, const size_t to) {
+    if (from >= to) {
+        return 0;
+    }
+    free_list(destination);
+    size_t start, i;
+    node_t* to_copy = list_ith_or_last(self, to, &start);
+    if (to_copy == NULL) {
+        return 0;
+    }
+
+    for(i = start; i > from; i--) {
+        node_t* copied = malloc(sizeof(node_t));
+        memcpy(copied, src, sizeof(node_t));
+        list_insert(destination, 0, copied);
+    }
+    
+    return start - from;
+}
+
+int list_insert(const list_t* self, const size_t position, const node_t* node) {
+    if (self->first == NULL) {
+        return 1;
+    }
+
+    if (position == 0) {
+        node->next = self->first;
+        node->prev = NULL;
+        self->first = node;
+        return 0;
+    }
+
+    node_t* to_reach = list_ith(self, position - 1);
+
+    if (to_reach == NULL) {
+        return 2;
+    }
+
+    to_reach->next->prev = node;
+    node->next = to_reach->next;
+    node->prev = to_reach;
+    to_reach->next = node;
+    return 0;
+}
+
+node_t* list_remove(const list_t* self, const size_t position) {
+    if(position == 0) {
+        node_t* to_remove = self->first;
+        self->first = to_remove->next;
+        return to_remove;
+    }
+
+    node_t* to_reach = list_ith(self, position - 1);
+    if (to_reach == NULL || to_reach->next == NULL) {
+        return NULL;
+    }
+
+    node_t* to_remove = to_reach->next;
+    to_reach->next = to_reach->next->next;
+    to_reach->next->prev = to_reach;
+    return to_remove;
+}