Erlang で家計簿の穴埋め

lunch.erl

-module(lunch).
-export([calc/0]).

calc() ->
  NDays = 7,
  TotalInThePeriod = 2290,
  Menus = [{set, 370}, {curry, 350}, {udon, 300}],
  Seq = lists:seq(0, NDays),
  Amounts = [[X, Y, Z] ||
             X <- Seq, Y <- Seq, Z <- Seq, X + Y + Z =:= NDays],
  Breakdowns = lists:map(
                 fun(Amount) ->
                   lists:zip(Menus, Amount)
                 end,
                 Amounts),

  lists:filter(
    fun(Breakdown) ->
      Total = lists:foldl(
                fun({{_, Price}, N}, Acc) ->
                  N * Price + Acc
                end,
                0, Breakdown),
      Total =:= TotalInThePeriod
    end,
    Breakdowns).