How to obtain the cost of each employee in Prolog?

问题

How would I be able to obtain the totalcost and loop through each employee to get the cost individually?

Expected output:

?- make_team([batman, superman, aquaman], Heroes, TotalCost).
Heroes = [[batman, bruce, wayne, 342000], [superman, clark, kent, 475000], [aquaman, arthur, curry, 5000]],
TotalCost = 822000.

% Returns a list of available heroes.
% Each hero's information is also stored as a list.
employees(E) :- E = [
  [superman, clark, kent, 475000],
  [batman, bruce, wayne, 342000],
  [wonder_woman, diana, prince, 297000],
  [green_arrow, oliver, queen, 210000],
  [flash, barry, allen, 184000],
  [aquaman, arthur, curry, 5000] ].

% Helper rule that may be used to extract information from an
% employee.  For instance, if you know an employee's name,
% you can use this rule to look up their salary.
hero(HeroName, SecretIdentFname, SecretIdentLname, Salary) :-
  employees(EmpList),
  member(H, EmpList),
  H = [HeroName, SecretIdentFname, SecretIdentLname, Salary].


% Given a list of hero names, return the list of heroes
% and the total cost of all heroes.  (Since there should
% only be one match, you might consider using a green cut).
make_team([], [], 0).
make_team([HeroName|Tail], HeroList, TotalCost) :-
  employees(EmpList),
 % CODE HERE

回答1:

employees(E) :- E = [
  [superman, clark, kent, 475000],
  [batman, bruce, wayne, 342000],
  [wonder_woman, diana, prince, 297000],
  [green_arrow, oliver, queen, 210000],
  [flash, barry, allen, 184000],
  [aquaman, arthur, curry, 5000] ].


make_team([], [], 0).
make_team([HeroName|Tail], HeroList, TotalCost) :-
    employees(EmpList),
    make_team(Tail, Z1, Z2),
    member( [HeroN, A, B, C], EmpList),
    HeroN == HeroName,
    append([[HeroN,A,B,C]],Z1,HeroList),!,
    TotalCost is Z2 + C.

Try that.

来源：https://stackoverflow.com/questions/61828694/how-to-obtain-the-cost-of-each-employee-in-prolog

标签

prolog

swi-prolog