Every message issued by the Prolog system is displayed using the
built-in predicate print_message/2. Similarly, all user input is
handled by the new built-in predicate ask_query/4. The behavior
of these predicates can be customized by a number of new hooks. For
example, all I/O can be redirected from the standard streams to Tcl/Tk
or similar windows. The default appearance of system messages has also
changed.
The mapping from Prolog terms representing messages to printed messages
is now completely transparent and customizable. The new
library('SU_messages') file defines the mapping rules.
Runtime systems can display system messages in standard format by
loading this file.
A number of new hooks have been added for the message and query system:
generate_message_hook/3, generate_message/3,
message_hook/3, print_message_lines/3,
query_hook/6, query_class_hook/5,
query_input_hook/3, query_map_hook/4.
See Messages and Queries.