[Computer-go] Definition of single-point eye

Peter Drake drake at lclark.edu
Fri Oct 24 08:05:11 PDT 2014

On Thu, Oct 23, 2014 at 11:36 PM, Robert Jasiek <jasiek at snafu.de> wrote:

> On 24.10.2014 01:19, Peter Drake wrote:
>> Isn't A an eye here?
>> .....
>> .xxx.
>> .xAx.
>> .xxx.
>> .....
>> (Remember, I'm trying to define "eye", not "life").
> If you want to use eye in a broader sense, then every region that is
> - connected via lines,
> - adjacent and only adjacent to the player's live stones,
> - containing empty intersections,
> - possibly containing dead opposing stones
> is an eye.

I believe A is an eye even though the stones to which it is adjacent are
not alive.

> "surrounded" is less exact than "adjacent and only adjacent to".
>> I'm not sure I understand your wording.
> Surrounded is ambiguous, adjacent and only adjacent to is exact. It is
> adjacent to something and it is only adjacent to the something and not to
> something else.

Very picky writing point: wouldn't "adjacent to the the player's live
stones and only to such stones" be slightly clearer than "adjacent and only
adjacent to the player's live stones"? The latter seems to read as
"adjacent to those stones and not having any other relation to those

>  I'm writing up some "how to play Go" flyers
>>> AGA rules.
> So you do NOT NEED ANY life, death and eyes!

Definitely! That's why I prefer AGA to Japanese. In AGA, life, death, and
eyes are consequences of the rules; in Japanese, they are part of the rules.

I already have this one-page summary of AGA rules:


The rules are in the left column. The rest are examples, which I think are
necessary in such a flyer.

The current project is a series of eight flyers which I am putting up in
bathroom stalls around campus. These explain things more slowly. The topics

   - Capturing
   - Liberties (no suicide)
   - Territory (neutral points)
   - Scoring (passing, komi)
   - Ko
   - Eyes (false eyes, removing dead stones)
   - Seki
   - Ranks (handicaps, online play)

Strictly speaking, the last three are of course unnecessary.

> AGA Rules are unnecessarily complicated in their text. They ought to drop
> life and death.

It is possible to explain the AGA rules without going into this.

The "concise" rules (http://www.usgo.org/files/pdf/conciserules.pdf) take
the interesting tack of defining life and death in terms of player
agreement; if there's a dispute, resume playing. Death is not a rule, just
a convenience for speeding up the game. This is probably reasonable for
rules meant to handle tournaments.

> A flyer must be short, so drop the unnecessary! Speak of "stones (not) on
> the board".

I generally agree on omitting needless words, but it is possible to be so
mathematically concise that the meaning becomes difficult to unpack.

> Read http://home.snafu.de/jasiek/asintro.pdf
> Note how I do NOT mention life, death, eyes.
>  AGA rules, of course, allow either area or territory scoring.
> AGA Rules, of course, use area scoring, do not use territory scoring,
> allow the area score to be determined by either area counting for area
> scoring or territory scoring for area scoring.

Fair enough (and correction in the next message noted).

> Your rules appear to be largely equivalent to AGA
> No, but ignore them if you want to use AGA style rules anyway.

Our club (and annual tournament) uses AGA rules, so that's what I prefer to

Peter Drake
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