The inclusion of set theoretical concepts in Prolog

Set-theoretical concepts, including the notion of intensional and extensional sets, are implemented in Prolog. Infinite as well as finite sets can be represented, and sets can be nested. This implementation allows for sets of lists and lists of sets. Users can specify the value of sets in a high-level sublanguage which corresponds closely to conventional logical notion, and the system automatically converts the specification to an efficient internal format. Set operations take intensional, extensional, or a mixture of intensional and extensional sets as inputs and return, if anything, a valid intensional or extensional set as output.<>