Add spreadsheet program

src/celltree.h

@@ -0,0 +1,21 @@
+#ifndef CELLTREE_H
+#define CELLTREE_H
+
+#include <stdbool.h>
+#include "cell.h"
+
+/* TODO: implement red-black tree */
+struct celltree {
+    struct cell     *cell;
+    struct celltree *right;
+    struct celltree *left;
+    bool             isRed;
+};
+
+void celltree_delete(struct celltree *root);
+
+struct cell *celltree_search(struct celltree *root, size_t x, size_t y);
+
+void celltree_insert(struct celltree **root, struct cell *c);
+
+#endif