/*
  https://puzzles9.com/puzzles/number-sequence-puzzles-with-answers/
  Puz254
  """
  5 6 7 4 9
  2 4 8 1 6
  7 5 4 7 1
  6 1 3 5 8
  4 2 6 ? 6

  Answer  :   3
  In the above puzzle, in each row , treat first two digits as one number and also last 
  two digits as one number. subtract last number from first number to get middle number.

  56  –  49  =  7
  24  –  16  =  8
  75  –  71  =  4
  61  –  58  =  3
  42  –  36  =  6

  So, answer is 3.
  """

  We rearrange to get the unknown last:
    5 6 7 9 4
    2 4 8 6 1
    7 5 4 1 7
    6 1 3 8 5
    4 2 6 6 ?

 This representation seems to be too hard. After about 50 minutes, still no solution is found.
 Here's the last generation before I aborted the run:
 """
 gen = 32591
 results_best = [[0.034522293124594,(A - C / C) * 1 + 5 / (D * D / (1 / 8) + (C - A))],[0.034522293124594,8 + (A - (10 - 1)) + 5 / (D * D / (1 / 8) + (C - A))],[0.034522293124594,A + (8 - 9) + 5 / (D * D / (1 / 8) + (C - A))],[0.034522293124594,3 - 4 + A + 5 / (D * D / (1 / 8) + (C - A))],[0.034522293124594,7 - 8 + A + 5 / (D * D / (1 / 8) + (C - A))],[0.034522293124594,5 - (6 - A) + 5 / (D * D / (1 / 8) + (C - A))],[0.034522293124594,7 - (8 - A) + 5 / (D * D / (1 / 8) + (C - A))],[0.034522293124594,9 - (10 - A) + 5 / (D * D / (1 / 8) + (C - A))],[0.034522293124594,A - 1 + 5 / (D * D / (1 / 8) + (C - A))],[1.2,A - 1 + (C / 10 - (D - 2) / 10)]]
 good = []
 """
  
 See below for an approach that's a little better.

*/

/*
data(puz254,Data,Vars,Unknown,Ops,Constants,MaxSize,Params) :-
  Matrix = [
            [5,6,7,9,4],
            [2,4,8,6,1],
            [7,5,4,1,7],
            [6,1,3,8,5],
            [4,2,6,6,_]
  ],
  % Ops = [+,-,*,/],
  Ops = [+,-,*,/,to_num2],  
  Constants = 1..10,
  make_data_matrix(Matrix,Data,Unknown,Vars),
  % make_data_matrix(Matrix.transp,Data,Unknown,Vars),
  MaxSize = 11,
  Params = new_map().
*/

/*
  A simpler variant.

  Let's simplify the problem a little and make the mid column
  the unknown instead:

    5 6 4 9  7
    2 4 1 6  8
    7 5 7 1  4
    6 1 5 8  3
    4 2 3 6  ?

  For this simple version we find these solutions.

  * With to_num2/2
  [program = to_num2(A - C,B - D),res = 6,count = 1]

  * Without to_num2/2 it's quite hard to find a solution
   program = C - (A - 6) + 3 + (C * (A - (3 + 4)) + (B + (D - (C + 4)))),res = 0,count = 1]
   
   (simplifies to 
    5 - A + B + (-7 + A) C + D
   )

*/
data(puz254,Data,Vars,Unknown,Ops,Constants,MaxSize,Params) :-
  Data = [ [[5,6,4,9],7],
           [[2,4,1,6],8],
           [[7,5,7,1],4],
           [[6,1,5,8],3]
        ],
  Unknown = [4,2,3,6],
  Vars = ['A','B','C','D'],
  % Ops = [+,-,*],
  Ops = [+,-,*,to_num2],  
  Constants = 1..10,
  MaxSize = 11,
  Params = new_map([init_size=1000,show_best=20]).