Findall
Description
An implementation of the findall relation.
Source: PROLOG programming for artificial intelligence, 3rd Edition, Harlow, 2001, ISBN 0-201-40375-7.
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% Figure 7.4 An implementation of the findall relation.
findall( X, Goal, Xlist) :-
call( Goal), % Find a solution
assertz( queue(X) ), % Assert it
fail; % Try to find more solutions
assertz( queue(bottom) ), % Mark end of solutions
collect( Xlist). % Collect the solutions
collect( L) :-
retract( queue(X) ), !, % Retract next solution
( X == bottom, !, L = [] % End of solutions?
;
L = [X | Rest], collect( Rest) ). % Otherwise collect th
e rest
RTERR: No permission to modify static procedure.