go =>
  A = [2, 4, 6, 8, 9],
  TestValues = [2,1,8,10,9,5],

  foreach(Value in TestValues)
    test(binary_search,A, Value)
  end,
  test(binary_search,[1,20,3,4], 5),
  nl.

% Test with binary search predicate Search
test(Search,A,Value) =>
  Ret = apply(Search,A,Value),
  printf("A: %w Value:%d Ret: %d: ", A, Value, Ret),
  if Ret == -1 then
    println("The array is not sorted.")
  elseif Ret == 0 then
    printf("The value %d is not in the array.\n", Value)
  else
    printf("The value %d is found at position %d.\n", Value, Ret)
  end.

binary_search(A, Value) = V =>
  V1 = 0,
  % we want a sorted array
  if not sort(A) == A then
    V1 := -1
  else
    Low = 1,
    High = A.length,
    Mid = 1,
    Found = 0,
    while (Found == 0, Low <= High)
       Mid := (Low + High) // 2,
       if A[Mid] > Value then
         High := Mid - 1
       elseif A[Mid] < Value then
         Low := Mid + 1
       else
         V1 := Mid,
         Found := 1
      end
    end
  end,
  V = V1.