[gnugo-devel] Re: how to specify constraints inside pattern?

[kevin yong]

Hi, Evan:

  please give me some help to understand how the
pattern works:


>From patterns.texi:

To give a simple example we consider a connection
pattern:

Pattern Conn311

O*.
?XO

:8,C,NULL

O*a
?BO

;oplay_attack_either(*,a,a,B)

Here we have given the label ‘a’ to the empty spot to
the right of the considered move and the label ‘B’ to
the ‘X’ stone in the pattern.

In this example we have a reading constraint which
should be interpreted as:

"Play an ‘O’ stone at ‘*’ followed by an ‘X’ stone at
‘a’. Accept the pattern if ‘O’ now can capture either
at ‘a’ or at ‘B’ (or both strings)."


Now let me try to interprete original pattern D301:

Pattern D301

X..?
O.*.
O..?

:8,Eb,value(80)

X..?
O.*a
O..?

;owl_escape_value(a) > 1

my interpretation:
O move at *, then check owl_escape_value about ‘a’ >
1. Here, we don’t mean X next move at ‘a’, do we?


Now, try to interprete the modification we try to put
on D301:

Pattern D301

X..?
O.*.
O..?

:8,Eb,value(80)

X..?
B.*a
B..?

;owl_escape_value(a) > 1 && !oplay_attack(*,B)

my interpretation:
‘O’ move at ‘*’, then oplay_attack on ‘B’, and it must
NOT success.

Should it be xplay_attack on ‘B’? I tried:

;owl_escape_value(a) > 1 && !xplay_attack(*,B)

but the pattern still got matched.

What we want to check here is: O move at *, then let X
attack ‘B’ to see if success. If no, accept pattern.
Then for this specific case 13x13:6, X attack on ‘B’
string will be success, because ‘B’ strings don’t have
enough liberties. Then pattern should be rejected for
13x13:6.

So, I still don’t think I have understand this fully
yet.


Now, let me try to interprete constraints for ED67:

The original version of pattern:

?x?         draw back for safety
O.X
.*O
...
...
---

:8,Oj

?x?
OaB
.*O
...
...
---

; xplay_defend(*,a,*) && !xplay_attack(*,a,B)

my interpretation (by following the example in
pattern.text):

1st constraint is: O play at ‘*’; X play at ‘a’; then
xplay_defend against ‘*’? and it must success.

2nd constraint is: O play at ‘*’; X play at ‘a’; then
xplay_attack against ‘B’? and it must NOT success.

Obviously, these interpretations are wrong. But I just
cant get it right.


thank you in advance.

kevin.



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