I'm a relatively new to Haskell, so I figured I needed to write a Sudoku solver. The key features of this solver are: * It's longer than other Haskell Sudoku solvers I've seen around * It fails to solve many solvable puzzles Fantastic! link: http://panicsonic.blogspot.com/2007/04/sudoku-solving.html The approach: Because I'm new to Haskell, the traditional guess-and-check method of Sudoku solving would involving things like backtracking down a search path, which is still in the realm of Haskell Black Magic. Instead, I cast the problem into successive function applications on data - A Sudoku puzzle is represented as an array of constraints on the values of cells. The constraints are reduced via analysis of the surrounding constraints until the puzzle is solved (or not). For those who like references: my approach is similar to "Solving Sudoku Puzzles with Rewritting Rules" by Gustavo Santos-Garcia and Miguel Palomino, 2005, Electronic Notes in Theoretical Computer Science. My main rules and techniques can be considered as generalizations on some of their rules and techniques - except their solver can solve all solvable puzzles (with the help of a guess-and-check rule). Thanks for taking a look, Antoine