Life In 19x19

I am currently reading the endgame book of the "Elementary Go Series"

I added a sample of the pages
(ch 2 p.4f)

I dont understand the number "2 (-)" in the result.
And what do the plus and minus mean ??


Pls enlighten me

It is seldom necessary to be precise when calculating the size of a play or territory. The plus or minus means a little more than or a little less than.

To be precise, in the original position, given the usual assumptions, a play by either player gains 3 1/3 points. The difference between the result when Black plays first and the result when White plays first is thus 6 2/3 points, or 7(-).

thanks for the clarification but could you explain how you calculated exactly?
even though its not necessary it would be nice to be able to do it.

How to get the exact count.

In Diagram 16 Black has 1/3 point in the corner for the White ko stone in atari. White has 4 points. (It is somewhat arbitrary what you count, but they seem to be counting 4 of White's points.) Net result: -3 2/3 points for Black (3 2/3 points for White).

If Black plays from Diagram 15 instead of White, the net result is -3.

Since the moves are gote, the count for Diagram 15 is -3 1/3.

In Diagram 14 the net result is 0.

Since the moves Diagram 13 are gote, the count for Diagram 13 is -1 2/3.

The count for Diagram 11 is +5.

The original count is +1 2/3. Either gote gains 3 1/3. The swing between Diagram 11 and Diagram 15 is 6 2/3.


Edit:

Before someone else points it out, in Diagram 16 is not exactly gote, since it gains 1/3 point and Black can also gain 1/3 point by taking the ko. Still, treating it as gote gives the right answer, as it is ambiguous.

in Diagram 12 is ambiguous, too, BTW. When the book was written go players did not understand about ambiguous plays.