prolog_listing.pl

/*
* This is a prolog code showing basic code patterns
* on how to write relationships between items and
* how to reason about them.
*/


has(jack,apples). % jack has apples.
has(jack,plums).  % jack has plums.
has(ann,plums).   % ann has plums.
has(dan,money).   % dan has money.
fruit(apples).    % apple is fruit.
fruit(plums).     % plums is fruit.

/*
* usage: swipl -q -f prolog_listing.pl -t fruit_listing
*/
fruit_listing :-
    listing(fruit), nl, halt.

/*
* usage: swipl -q -f prolog_listing.pl -t fruit_listing
*/
main :-
    has(X,apples),    % who has apples
    has(Y,money),     % who has money
    write(X),         % write apple owner
    put(10),          % new line
    write(Y),         % write money owner
    nl, halt.         % new line and halt