/*-------------------------------------- File: chores1.ecl -------------------------------------

Title: Solving Logic Puzzles using Artificial Intelligence

Author: Leon J. Mekly, Ph.D.
	Modified to use pure Prolog with backtracking by Joachim Schimpf

Knowledge representation language: ECLiPSe CLP at https://eclipseclp.org

Example: "At the farm" - rated HARD
    https://www.ahapuzzles.com/logic/logic-puzzles/pdf/at-the-farm.pdf

    Five siblings (one is Fran) live on a farm. Each must perform a chore
    (including milking a cow) on a specic day of the week (Mon-Fri).
    If each of them performs a certain task on a given day and at a specic
    time (either 5:00 am, 6:00 am, 7:00 am, 8:00 am, 9:00 am), from the clues
    provided below can you determine which sibling performed which task
    at which time on which day?
----------------------------------------------------------------------------------------------------*/

:- lib(listut). % for perm/2 list permutation

go :-
        Farm = [
            ['Adam', AdamDay, AdamTime, AdamChore],
            ['Carl', CarlDay, CarlTime, CarlChore],
            ['Fran', FranDay, FranTime, FranChore],
            ['Nan ', NanDay , NanTime , NanChore ],
            ['Mike', MikeDay, MikeTime, MikeChore]
        ],
        Days = [AdamDay,CarlDay,FranDay,NanDay,MikeDay],
        [Mon,Tue,Wed,Thu,Fri] = [1,2,3,4,5],
        perm(Days, [Mon,Tue,Wed,Thu,Fri]),

        Chores = [AdamChore,CarlChore,FranChore,NanChore,MikeChore],
        perm(Chores, [milk,market,corn,fences,eggs]),

        Times = [AdamTime,CarlTime,FranTime,NanTime,MikeTime],
        perm(Times, [5,6,7,8,9]),

    % 1. Fran's day to mend fences is neither Tuesday nor Thursday, and is
    % completed earlier in the week than at least one other person.
        member(['Fran',FranDay,_,fences],Farm),
        FranDay \= Tue, FranDay \= Thu, FranDay < Fri,

    % 2. The one who goes to market goes later in the week than Carl, and
    % earlier in the morning than Nan, but later in the morning than Fran.
        member(['Mike',MikeDay,MikeTime,market],Farm), % Mike is the one in clue 9
        MikeDay > CarlDay, MikeTime < NanTime, MikeTime > FranTime,

    % 3. Adam does not plant the corn, or go to market, his chore is completed
    % before 9:00 am, but not before 6:00 am on his assigned day of Monday.
        AdamChore \= corn, AdamChore \= market,
        AdamTime < 9, AdamTime >= 6, AdamDay = Mon,

    % 4. No one performs a chore on Thursday at 7:00 am.
        member([_,Thu,ThuTime,_],Farm), ThuTime \= 7,

    % 5. Mike's chore is completed earlier in the day than at least 3 others,
    % but later in the week than at least three others.
        MikeTime < 7, MikeDay > Wed,

    % 6. One of the boys collects eggs, another boy milks Bessie, the goat.
        member([_,EggsDay,EggsTime,eggs],Farm),
        member([_,MilkDay,_,milk],Farm),

    % 7. The milk is collected earlier in the week than the girl who plants
    % the corn, which is not planted before Wednesday.
        member(['Nan ',CornDay,_,corn],Farm), % Nan is the girl, Fran mends fences
        MilkDay < CornDay, CornDay > Tue,

    % 8. The eggs must be collected at 7:00 am, but never on Mondays or Fridays.
        EggsTime = 7, EggsDay \= Mon, EggsDay \= Fri,

    % 9. All the other chores must be complete before Mike goes to the market.
        MikeChore = market, MikeDay = Fri, nl,
        (foreach(Sibling,Farm) do writeln(Sibling)).

%-------------------------------------- EOF: chores1.ecl -----------------------------