Add spreadsheet program

src/cell.h

@@ -0,0 +1,38 @@
+#ifndef CELL_H
+#define CELL_H
+
+#include <stddef.h>
+#include <stdint.h>
+#include <time.h>
+#include "common.h"
+
+enum cell_type {
+    Text,
+    Integer,
+    Floating,
+    Date
+};
+
+struct cell_list {
+    struct cell      *cell;
+    struct cell_list *next;
+};
+
+struct cell {
+    struct cell_list *referenced_by;
+    size_t            x_pos;
+    size_t            y_pos;
+    char             *text;
+    enum cell_type    type;
+    union {
+        int64_t integer;
+        double  floating;
+        time_t  date;
+    } value;
+};
+
+void cell_init(struct cell *c, size_t x_pos, size_t y_pos, enum cell_type type);
+void cell_delete(struct cell *c);
+void cell_set_type(struct cell *cell);
+
+#endif