> That is not possible, because the environment can (and at some point always will) change which wasn't planned for due to a lack of working crystal balls. Data

> That is not possible, because the environment can (and at some point always will) change which wasn't planned for due to a lack of working crystal balls. Data, user behavior, the network, the system(s) the software runs on can all change over time. It sounds to me like you are describing a change of problem, not bugs in the solution. If in the future someone redefines the concept of a Sudoku puzzle such that this solution is no longer applicable, or tries to use the solution verbatim in a language which is different from K and therefore yields different results, it's not a bug in the original code that it's not a solution to that new problem. It's still a solution to the same problem it was always a solution to. I can see what you mean in a practical sense, but also consider (practically) that a lot of problems can be broken down into smaller, well-defined problems which are themselves practically immutable. You can throw the solutions to such problems out when you no longer need them, and come up with solutions to whatever new problems replaced the original problems.