/* 

  Farmer wheat/corm problem in Picat.

  From IF/Prolog Constraint manual (cons.pdf)
  page 31,
  """
  A farmer can grow wheat or corn on his field. Each produces a different yield 
  per unit of area of land but also requires a different amount of time for 
  its care; there is also a limit to the maximum amount of work time. 

  """


  This Picat model was created by Hakan Kjellerstrand, hakank@gmail.com
  See also my Picat page: http://www.hakank.org/picat/

*/


% import util.
% import cp.
import mip.

main => go.


go =>
  
  Area = 100,        % total available area
  WorkTime = 40,     % maximum work time
  OutputCorn = 5/2,  % corn yield per unit area
  OutputWheat = 7/2, % yield per unit area
  CostsCorn = 1/3,   % time spent per unit area for corn
  CostsWheat = 2/3,  % time spent per unit area for wheat
  % | all_positive([AreaCorn, AreaWheat]),
  AreaCorn #>= 0,
  AreaWheat #>= 0,
  Area #>= AreaCorn + AreaWheat,
  WorkTime #>= CostsCorn * AreaCorn + CostsWheat * AreaWheat,
  Output #= AreaCorn * OutputCorn + AreaWheat * OutputWheat,
  % | linear_maximize(Output, MaxOutput).

  solve($[max(Output)], Output),

  println(output=Output),
  println(area=Area),
  println(workTime=WorkTime),
  println(outputCorn=OutputCorn),
  println(outputWheat=OutputWheat),
  println(costsCorn=CostsCorn),
  println(costsWheat=CostsWheat),
  println(areaCorn=AreaCorn),
  println(areaWheat=AreaWheat),

  nl.