Re: [Haskell-cafe] My knight's tour does not seem to end

Isn't mark is always increasing the size of the board? - I haven't run the code but I if this is the behaviour you want 'mark' is probably not a good name (I'd expect mark to be returning something the same size but with marked elements). In _mark_ the before and after are always splits, so the concatenation on the first line of the definition of _mark_ is taking the splits and adding more between them thus expanding the board.