Differences in the User Interfaces

The Lambda--prl and Nuprl user interfaces are nearly identical, although there are two noticeable differences.

• In Nuprl the eval command invokes an interactive evaluation facility, into which one enters terms and bindings to be evaluated. EVAL objects residing in the library may contain def refs. In Lambda--prl the eval command has the form eval term, and term may not contain definition references.

• In Lambda--prl , identifiers can include the pound sign (`` #'') in addition to the alphanumeric characters and the underscore (`` _''). In Nuprl , the at sign (`` @'') is used instead of the pound sign. Note that users are encouraged not to use at signs in their own identifiers, since the system implementers have reserved them for their own purposes.