Marcel Popescu

I have long been a fan of Fabian Pascal's database ramblings (not his political and economical ones, the man has absolutely no clue on those). Yes, the relational theory is actually set algebra, and therefore a relational database is the most complete and powerful type of database, bar none. Object databases, hierarchical databases (registry), network databases (objects) - they all have problems which simply do not exist in an RDB. However, I was re-reading an article about the object / relational mismatch problem - Interoperability happens and I got to this part: Developers simply give up on relational storage entirely, and use a storage model that fits the way their languages of choice look at the world. Object-storage systems, such as the db4o project, solve the problem neatly by storing objects directly to disk, eliminating many (but not all) of the aforementioned issues; there is no "second schema", for example, because the only schema used is that of the object d

For the last few months, I've been trying on and off to write a program to solve a Sudoku game. The "easy" ones are easy, you just use a rudimentary algorithm: each cell has a list of possible values associated with it start by associating all values 1-9 to each cell repeat until solved: for each cell, remove any values already present in the same line, column, or box By this process of repeated elimination you can solve a lot of the "easy" tables. However, this algorithm is too limited and it will go into an infinite loop if you have a situation where, for example, two cells in the same row can accept values 1 and 5, but at this point you have no way of knowing which is which. Now, of course the solution to that problem is simply a recursive backtracking algorithm: save the current state pick one value and try to solve the rest of the table; if it worked, all is good; if not, go back to the saved state and try the next value The devil, however, is in the deta