From: Travis Smith <zultan.durin@...>
Date: 2005-08-24T02:39:00+09:00
Subject: Re: [QUIZ] Sodoku Solver (#43)

On 8/23/05, Adam Shelly <adam.shelly@gmail.com> wrote:
> 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

You can always recuse it, then throw it again if you don't want it. At
least I assume so... I've never tried to do it in Ruby.


-- 
~Travis