typedef struct BooleanVar BooleanVar;
typedef struct BooleanLogic BooleanLogic;
typedef struct BooleanComp BooleanComp;
+typedef struct BooleanPredicate BooleanPredicate;
struct Boolean;
typedef struct Boolean Boolean;
typedef struct Set Set;
typedef struct Set MutableSet;
+typedef struct ElementFunction ElementFunction;
+typedef struct ElementSet ElementSet;
+
struct Element;
typedef struct Element Element;