Sum up data from facts

问题

(Given a list of movies, write a PROLOG rule to add and display the total takings.) This is my question I am basically trying to add an integer value give a list of movies from the list below. I am quite new in Prolog and I don't really understand how things work.

takings(air_force_one,315000000).
takings(american_beauty,336000000).
takings(american_pie,201700000).
takings(american_wedding,230700000).
takings(armageddon,554600000).
takings(as_good_as_it_gets,313300000).
takings(austin_powers_in_goldmember,289000000).
takings(babe,249000000).
takings(back_to_the_future,350600000).
takings(back_to_the_future_part_ii,332000000).
takings(back_to_the_future_part_iii,243700000).
takings(robots,245600000).
takings(hulk,241700000).
takings(bad_boys_ii,261900000).

The Rule I have written so far works for only one movie. Example:

?-  score([robots],Y).
    Y = 245600000.

?- score([robots,hulk],Y).
false.

?- score([robots,hulk,bad_boys__ii],Y).
false.

Rule written :

score([Movies], Money):-
    findall(Profit,(takings(Movies, Profit)), ListOfProfit),
    sum_list(ListOfProfit, Money).

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Related question asking for a recursive answer.

回答1:

What you seek is

score(Movies,Total) :-
    findall(Money,(member(Movie,Movies),takings(Movie,Money)),Profit),
    sum_list(Profit,Total).

The parts you needed are

1. You can put more than a simple query in the Goal for findall/3, e.g.

(member(Movie,Movies),takings(Movie,Money))

2. [Movies] is used wrong as needed. It should be just Movies

---

Example run

?- score([robots,hulk,bad_boys_ii],Y).
Y = 749200000.

来源：https://stackoverflow.com/questions/60580787/sum-up-data-from-facts