The DBInt struct below implements an integer type that can represent the complete set of values of the int type, plus an additional state that indicates an unknown value. A type with these characteristics is commonly used in databases. (DBInt x, DBInt y) { return x.defined && y.defined? x.value > y.value: DBBool.Null; } public static DBBool operator <(DBInt x, DBInt y) { return x.defined && y.defined? x.value < y.value: DBBool.Null; } public static DBBool operator >=(DBInt x, DBInt y) { return x.defined && y.defined? x.value >= y.value: DBBool.Null; } public static DBBool operator <=(DBInt x, DBInt y) { return x.defined && y.defined? x.value <= y.value: DBBool.Null; } } ]]>