setof/3

creates a sorted list with all solutions of a goal for all instantiations of the free variables in that goal with duplicates removed.

setof(+Term, +(Template ^ Goal), ?TermList)
setof(+Term, +Goal, ?TermList)

setof/3 unifies TermList for each different instantiation of the free variables in Goal with a sorted list of all instantiations of Term where Goal is a solution of Term. Duplicates will not be part of the list.
Each variable, wich occurs in Goal and does not occur in Term or Template is called a free variable.

Arguments

Term                   term
Template               term
Goal                   goal
TermList               list

Examples

part_of(house, window).
part_of(house, door).
part_of(house, room).
part_of(room, table).
part_of(room, floor).
part_of(floor, tile).

contains(X, Y) :- part_of(X, Y).
contains(X, Y) :- part_of(X, Z), contains(Z, Y).

?- setof(Element, contains(What, Element), List).

Element = _1
What    = house
List    = [door,floor,room,table,tile,window] ;

Element = _1
What    = room
List    = [floor,table,tile] ;

Element = _1
What    = floor
List    = [tile]

?- setof(Element, What ^ contains(What, Element), List).

Element = _1
What    = _2
List    = [door,floor,room,table,tile,window]

?- setof(Element, contains(house, truck), List)

no

Standard

This predicate is part of the ISO-Prolog Standard.

See also

bagof/3, findall/3.