RE: computer-go: Live or Die

[Daniel Hallmark <dgh@xxxxxxxxx>]

On Tue, 7 Dec 1999, Jeff Massung wrote:

> Okay, I think I might be misunderstanding eyes then.  I thought the 
> definition of an eye, was an enclosed territory where either (a) the enemy 
> cannot enter or (b) it is useless for the enemy to try and enter.

(a) would only be true (to my knowledge) in the case of a single-point eye
of an unconditionally alive group.

As for (b), if a group has only one eye space, it may be necessary for an
opponent to play inside that space to prevent the formation of a second eye.
There's nothing to keep you from using the above definition of an eye,
but keep in mind the separate concept of "eye space".  This would
be points which are current or potential eyes for a group, and which may be 
subject to an opponents attack.


> Because 'o' could still capture
> 
> ooooo    ooooo    ooooo    ooooo
> oxxxo    oxxxo    oxxxo    o...o
> ox.xo => oxoxo => ox.xo => o.o.o
> ox.xo    ox.xo    oxxxo    o...o


'o' can still capture because the group has only a single eye and no
ability to form a second eye to become a 'live' group.  To me, this 
doesn't mean that the 'x' group doesn't have an eye; it just means that 
it is a dead group.  You certainly could make an argument for defining an
"unconditional eye" as eye space in an unconditionally alive group which 
contains insufficient space for an opponent to live inside or fill, but
I think most folks intend a less strict meaning for the word 'eye' in 
general usage.

Daniel Hallmark