 The complex types, schematizable as "X/Y" and "X\Y", denote functor types that take an argument of type "Y" and return an object of type "X".A forward slash denotes that the argument should appear to the right, while a backslash denotes that the argument should appear on the left.Any type can stand in for the "X" and "Y" here, making syntactic types in CCG a recursive type system.