Prolog's default ways of eliciting keyboard input are enumerated in
the clauses for query_abbreviation/3
in messages(language('QU_messages.pl')). These clauses specify valid
abbreviations for a given key word. For example,
query_abbreviation(yes_or_no,'(y/n)',[yes-"yY",no-"nN"]).
A French translator might decide that the letters O and o are
reasonable abbreviations for oui (yes), and therefore write
yes-"oO". See the reference page for more information on
query_abbreviation/3.
The query hook provides a means of overriding the default interaction.
Whenever Prolog attempts to solicit input from the user, it first
looks to see if the application wants to take control of the query by
calling user:query_hook/6 (see the above figure). The
various queries are listed in the manual page for query_hook/6.
For example, if Prolog is looking for a yes-no response, as in the
toplevel, this request for input can be captured as follows, where
my_yes_no/2 binds Answer to yes or no:
query_hook(toplevel,_,_,_,_,Answer):-
my_yes_no('Done?',Answer).