Notcher Code

  Difficulty: Intermediate   Keywords: Life & Death

On this page we devise a coding system for notchers, in order to set up a systematic approach to their life and death status.

Suppose the notcher is black and the surrounding group white.

[Diagram]
Notcher 112NS = nabxy  

Below squared stones (black+square): notch (n)

Circled stones (black+circle): legs (ab)

Cross marked (cross): hips (xy)


  1. The notcher has a notch of n spaces.
  2. The notcher has a left leg of length a and a right leg of length b. The legs are the (black) stones on the second line.
  3. The notcher has a degree of weakness, x on the left hip and y on the right hip:
    • The letter W means that the hip is white (weak or an (angle) wedge),
    • N means that the stone on the hip is absent (neutral),
    • while S means that it is black (solid or strong).

We put this information into a code nabxy, where n, a, b take numerical values, and x and y can be either W, N or S.

The status of the notcher assumes no outside liberties and no escape threat (e.g. a descent that threatens to live and to escape). That would have to be covered by a second status in parentheses or the like.

The code is leg-normal if

  • a < b or
  • a = b and x <= y (W < N < S: weaker before stronger)

It is hip-normal if

  • x < y or
  • x = y and a <= b

Use leg-normal if you put up a page. Use hip-normal if you search in the Table of Notchers (that gives tables of reasonable size). A flip might be necessary: an exchange of a and b as well as x and y.

See Table of Notchers for lots of examples.


Notcher Code last edited by RobertPauli on January 20, 2018 - 15:16
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