Version 1.9 offers better portability including an MS-Windows 3.1
version. Changes to the Prolog system include:
- Redefinition of system predicates
Redefinition of system predicates was allowed silently in older
versions. Version 1.9 only allows it if the new definition is headed by
a :- redefine_system_predicate/1
directive.
- `Answer' reuse
The toplevel maintains a table of bindings returned by toplevel goals
and allows for reuse of these bindings by prefixing the variables with
the $ sign. See section 2.8.
- Better source code administration
Allows for proper updating of multifile predicates and finding the
sources of individual clauses.