+line_t *new_line() {
+ line_t *x = malloc(sizeof(line_t));
+ return x;
+}
+
+line_t *next_line(line_t *prev) {
+ line_t *x = new_line();
+ x->prev = prev;
+ prev->next = x;
+ return x;
+}
+
+page_t *new_page() {
+ page_t *x = malloc(sizeof(page_t));
+ return x;
+}
+
+page_t *next_page(page_t *prev) {
+ page_t *x = new_page();
+ x->prev = prev;
+ prev->next = x;
+ return x;
+}
+
+document_t *new_document() {
+ document_t *x = malloc(sizeof(document_t));
+ return x;
+}
+