Re: computer-go: What makes a ladder

["Njoroge" <Njoroge@xxxxxxxxxxx>]

> >The ladder fails if:
> >    - L2 is found to be a black stone
> >    - O has less than 2 liberties
> >
> >The ladder is successful if:
> >    - L2 is either outside the board or is a white stone
> >    - L2 is a black stone with only 2 or less liberties
> >    - L2 is a black stone on the edge with only 3 or less liberties
> >    - L2 is a black stone in the corner with only 4 or less liberties
>
> >Is this always true?
>
> No.  Two similar positions, upper edge, Black to play:
>
>  -.-.-.-.-.-.-.-.-.-.-       -.-.-.-.-.-.-.-.-.-.-
>   . . . . . . . . . .         . . . . . . . . . .
>   . . . . . . . . . .         . . . . . . . X . .
>   . . . . . . X . . .         . . . . . . . . . .
>   . O . . . . . . . .         . O . . . . . . . .
>   . O X O . . . . . .         . O X O . . . . . .
>   . . O . . . . . . .         . . O . . . . . . .
>   . . . . . . . . . .         . . . . . . . . . .
>
>   Black can save the          Black can't save the
>   ladder stone.               ladder stone.

I belive that you are wrong.

The rules that fails the ladder is that the Opponent stone has less than 2
liberties.

-.-.-.-.-.-O-.-.-.-.-
 . . . . O X . . . .
 . . . O X X O X . .
 . . O X X O . . . .
 . O X X O . . . . .
 . O X O . . . . . .
 . . O . . . . . . .
 . . . . . . . . . .

The ladder has now been extended and it is black to play.  The correct
orientation of my original diagram is

. L .
# a L
. O .

All checks take place when # plays at a.  When that happens above O has only
1 liberty which forces O to defend

-.-.-.-.-2-O-1-.-.-.-
 . . . . O X X 3 . .
 . . . O X X O X . .
 . . O X X O O . . .
 . O X X O . . . . .
 . O X O . . . . . .
 . . O . . . . . . .

After O defends # plays at 1, O defends at 2 and # saves his stones with 3.

I think..