Unconstraining genericity

Generic classes and especially generic collection libraries can be of great benefit for efficient software production. Constrained genericity is used to guarantee that the type provided as a parameter to a generic class such as a sorted list will offer the methods that class requires. We argue that constrained genericity is not really the appropriate mechanism for this purpose since it restricts a generic class to one kind of use for each element type. We introduce the concept of 'generic procedure parameters' which allow the properties of a collection class to be specified in the instantiation rather than via the properties of the elements. We show that the concept is very efficiently implementable, more powerful than constrained genericity and more useful for the practical construction of complex data collections.