+typedef struct {
+ BDDSET varset;
+ int size;
+} variables;
+
+typedef struct
+{
+ BDD bdd;
+ variables vars;
+} state;
+
+typedef struct
+{
+ BDD bdd;
+ variables varset;
+} trans;
+
+typedef enum { LEFT, UP, RIGHT, DOWN } direction;
+
+state *encode_screen(sokoban_screen *screen);