/* 

  Voltage divider problem in Picat.

  Problem from Marriott & Stuckey Programming in Constraints, page 137ff 

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

*/

import mip.

main => go.


go =>
  %% Goal for voltage divider program page 138.
  V  :: -100.0..100.0,
  R1 :: -100.0..100.0,
  R2 :: -100.0..100.0,
  VD :: -100.0..100.0,
  ID :: -100.0..100.0,
  I  ::  -100.0..100.0,
  cell(V),
  resistor(R1),
  resistor(R2),

  voltage_divider(V, I, R1, R2, VD, ID),
  5.4 #<= VD,
  VD #<= 5.5,
  ID #= 0.1,

  solve([V,I,R1,R2,VD,ID]),

  println([V,I,R1,R2,VD,ID]),
  
  nl.


%%
%% Rules for voltage divider program page 138
%%
voltage_divider(V, I, R1, R2, VD, ID) =>
     V1 :: -100.0..100.0,
     I2 :: -100.0..100.0,
     V1 #= I * R1,
     VD #= I2 * R2,
     V #= V1 + VD,
     I #= I2 + ID.



cells(Cells) => Cells = [9.0,12.0].
cell(C) =>
  cells(Cells),
  member(C, Cells).

resistors(Resistors) => Resistors = [ 5.0, 9.0, 14.0 ].
resistor(R) =>
  resistors(Resistors),
  member(R,Resistors).