findall/3

The predicate findall/3.

findall/3 is a predicate for finding all solutions to a goal or a sequence of goals. Queries of the form

findall(+Object, +Goal, -List)

compute a list of all instantiations of Object that satisfy Goal. The query

?- findall(X, happy(X), L).

for example, would give you a list of all instantiations of X such that happy(X) is satisfied. Object doesn't necessarily have to be a variable. For example,

?- findall(happy_duck(X), (happy(X), duck(X)), L).

would give you a list with all instantiations of happy_duck(X) such that happy(X), duck(X) is satisfied. So, assuming that your database looks as follows

duck(tick).
duck(trick).
duck(track).
duck(dagobert).
 
happy(tick).
happy(trick).
happy(track).

Prolog would answer

L = [happy_duck(tick), happy_duck(trick), happy_duck(track)]