/* 

  Simultaneous_pleasure in Picat.

  From https://enigmaticcode.wordpress.com/2021/12/04/puzzle-142-simultaneous-pleasure/
  """
  Puzzle #142: Simultaneous pleasure

  From New Scientist #3363, 4th December 2021

      :-) :-) :-)  + :-( :-(     = 22 (3 happy faces + 2 sad faces = 22)
      :-) :-)      + :-( :-( :-( = 23 (2 happy faces + 3 sad faces = 23)

    During lockdowns, I researched viral internet maths sensations. Several of them are 
    what a teenager might recognise as simultaneous equations. In the emoji example above, 
    smiley faces = 4 and blown minds = 5. Simultaneous equations without emojis are less 
    likely to go viral, but can be more fun. Here are two of my favourites.

    1. A pen and a pencil cost £1 together. The pen costs 90p more than the pencil. 
       How much do they each cost?

    2. There are some cows and some chickens in a field. I can see 40 eyes and 64 legs. 
       How many are there of each animal?

  """

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

*/

import cp.

main => go.

% 1. A pen and a pencil cost £1 together. The pen costs 90p more than the pencil. 
%    How much do they each cost?
%
go ?=>
  Pen :: 0..100,
  Pencil :: 0..100,

  Pen + Pencil #= 100,
  Pen #= Pencil + 90,

  solve([Pen,Pencil]),
  println([pen=Pen,pencil=Pencil]),
  fail,
  nl.
go => true.

%
% 2. There are some cows and some chickens in a field. I can see 40 eyes and 64 legs. 
%    How many are there of each animal?
%
go2 ?=>
  Cows :: 0..100,
  Chickens :: 0..100,

  Cows * 2 + Chickens * 2 #= 40, % 40 eyes
  Cows * 4 + Chickens * 2 #= 64, % 64 legs

  % solve([Cows,Chickens]),
  println([cows=Cows,chickens=Chickens]),
  nl,
  fail,
  nl.
go2 => true.


%
%  :-) :-) :-)  + :-( :-(     = 22 (3 happy faces + 2 sad faces = 22)
%  :-) :-)      + :-( :-( :-( = 23 (2 happy faces + 3 sad faces = 23)
%
go3 ?=>
  Happy :: 0..23,
  Sad :: 0..23,

  3 * Happy + 2 * Sad #= 22,
  2 * Happy + 3 * Sad #= 23,  

  % solve([Happy,Sad]),
  println([happy=Happy,sad=Sad]),
  nl,
  fail,
  nl.
go3 => true.