From: Adam Shelly <adam.shelly@...>
Date: 2005-08-24T02:31:48+09:00
Subject: Re: [QUIZ] Sodoku Solver (#43)

On 8/23/05, James Edward Gray II <james@grayproductions.net> wrote:
> Looking good.  Here's a few general Ruby style tips.  Feel free to
> ignore, if your not interested:
> 
> 1.  An easier way to write `print "line\n"` is `puts line`.
> 2.  Instead of using the dprint() method and commenting out the

thanks
> 3.  You can drop those outer parenthesis for if statements.  `if
> (condition)` can be just `if condition`.

I know, but C programmer habits die hard.  just looks funny without them...

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.
I wanted to do something like this pseudocode:

def solve
    deduce
    startGuessing if !solved
    return solved
end

def deduce
    ...work...
    raise BadGuess if conflict
end

def startGuessing
  @depth+=1
  begin
    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
  rescue UnsolvableBoard if @depth == 1   # this doesn't work.
      # if I remove the if, I end up at the level I started with.
     # and putting the rescue in the solve function doesn't help either.
      # ? So can I get back to the next candidate on the 1st level,
     # without checking return codes the whole way down
     # (which is what I ended up doing)?
  end
end


Thanks for any ideas,
-Adam