From: Jim Weirich <jim@...>
Date: 2005-08-24T02:53:19+09:00
Subject: Re: [QUIZ] Sodoku Solver (#43)

Adam Shelly said:
> So here's one thing I couldn't figure out last night, maybe someone can
> help me:
> I wanted to throw an exception in the middle of a pair of recursive
> functions, and catch it at the beginning of recursion.   But I can't
> figure out where to put the rescue.

You could try something like this:

  def search_for_solution
    solve
  rescue UnsolvableBoard
    # Handle Unsolvable Boards ...
  end

  def solve
    while candidates do
      begin
        guess #chose a candidate
        cloneBoard.solve  #with that candidate
     rescue BadGuess
        #go on to next candidate
      end
    end #while
    raise UnsolvableBoard  if !solved
  end

-- 
-- Jim Weirich     jim@weirichhouse.org    http://onestepback.org
-----------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct,
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)