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Dec 27th VH
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alanr555



Joined: 01 Aug 2005
Posts: 198
Location: Bideford Devon EX39

PostPosted: Fri Dec 28, 2007 11:57 am    Post subject: Reply with quote

keith wrote:

Not proposing to send people to other sites, but ...


There is such a thing as "brand loyalty"!!
I would hope that members of this forum can bring ideas from
elsewhere and contribute them here. I use no other SuDoku site
apart from this one. I was impressed by what SamGJ had to offer
in 2005 and by his open responses to ideas (and clamour even!)
for enhancements. The site now provides an excellent resource for
those interested in the subject matter.

Having looked at the proffered links, the first two present the topic in
a very algebraic way - a "turn off"! This further compliments Tracy
on her ability to transform the algebra into intelligibility.

The third site was interesting - although I did not delve into ALS (do
I need to know about it????).

There was mention on a WXYZ-wing.
Is this the same as the W-wing that is sometimes mentioned by
contributors to this forum?
Naively, I assumed that the "W" referred to the shape of a
two-dimensional pattern on the grid. Perhaps I was mistaken.

Anyway the WXYZ definition is developing as

"Where four cells contain only four unique digits within their profiles
and one digit (the "common" digit) is present in each of them
and the group contains three cells that would form a normal triple
if the common digit is disregarded
and the fourth cell is in direct contact (by line or region) with at least
one member of the triple,
then -
The common digit may be eliminated from any other cell which is in
direct contact (by line or region) with ALL four of the group."

Is this a correct interpretation?
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Fri Dec 28, 2007 2:03 pm    Post subject: Reply with quote

Alan wrote:
There was mention on a WXYZ-wing.
Is this the same as the W-wing that is sometimes mentioned by
contributors to this forum?


No. What is mentioned as the W-wing is named in honor of the first person from this forum who mentioned the pattern. It had been discussed on other forums earlier and named differently. There is discussion of the W-wing in this thread

The WXYZ-wing is an extension of the XYZ-wing which is an extension of the XY-wing. Basically the number of letters in front of the -wing tell one how many digits are in the pivot cell, which may be why it is referred to as that.
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Marty R.



Joined: 12 Feb 2006
Posts: 5732
Location: Rochester, NY, USA

PostPosted: Fri Dec 28, 2007 4:59 pm    Post subject: Reply with quote

Alan,

Not trying to argue, but just for the sake of discussion:

Quote:
I have amended my definition accordingly.

What's wrong with "When a cell XYZ sees both an XZ and YZ cell, no cell seeing all three of XYZ-XZ-YZ can contain Z."?

Quote:
I would still maintain that the concept of a pivot cell is irrelevant to
the implications of the pattern (unlike the case of the xy-wing) and
so I make no reference to it in my definition. From my point of view
mentioning the word "pivot" in relation to xyz just introduces an
unwanted mental association with xy. The two patterns are quite
different in nature and using separate language for them assists
with "grounding" such separate natures.

What's the harm? People understand the term. In both the XYZ and XY, the pivot cell is the one that sees the other two cells.

Quote:
but xyz-wing is a totally artificial name anyway!

Probably true. But artificiality seems to be part of the whole thing, and adds to the fun, what with kites, skyscrapers, Medusa, ocean-dwelling creatures, squirmbags, and the like. Wink Laughing

Quote:
This further compliments Tracy on her ability to transform the algebra into intelligibility.

I've never seen Tracy do any gender disclosure. Do you know something we don't? Question Laughing
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alanr555



Joined: 01 Aug 2005
Posts: 198
Location: Bideford Devon EX39

PostPosted: Sat Dec 29, 2007 3:00 am    Post subject: Reply with quote

Marty R. wrote:
Alan,
What's wrong with "When a cell XYZ sees both an XZ and YZ cell, no cell seeing all three of XYZ-XZ-YZ can contain Z."?


Probably nothing but some of us have difficulty with algebraic notation.
Thus I (!) could not say if anything is wrong with that definition - but
others may well be able to confirm that it is correct.


Quote:

Quote:
I would still maintain that the concept of a pivot cell is irrelevant to
the implications of the XYZ-wing pattern.

What's the harm? People understand the term. In both the XYZ and XY, the pivot cell is the one that sees the other two cells.


No harm as such - just confusion.
In the XY-wing the role of the pivot is pivotal!
(It defines which cells are pincers)
With XYZ-wing the important thing is ALL THREE cells being seen
by the fourth cell and the way that the trio is compiled has no
bearing on the implication - provided that the trio obeys the rules.


Quote:

Artificiality seems to be part of the whole thing, and adds to the fun,
what with kites, skyscrapers, Medusa, ocean-dwelling creatures, squirmbags, and the like. :wink: :lol:


Clearly my education is lacking - but I will await publication of a
puzzle where the solution uses these techniques before I ask
anyone to elucidate.

I have seen references to Medusa colouring and wonder what heads
will grow when one is amputated!
There are red Kites in mid-Wales (an endangered species) but are
the SuDoku kites like the birds or the aerial toys, I wonder. As for
skyscrapers, I presume that those of us who live outside the main
population centres will know of them only by repute.

Quote:

Quote:
This further compliments Tracy on her ability to transform the algebra into intelligibility.

I've never seen Tracy do any gender disclosure. Do you know something we don't? :?: :lol:


No. I apologise if I have erred.
I have fallen victim to cultural assumptions which apply in the UK but
do not necessarily have application globally.
In the UK "Tracy" is a feminine forename but I accept that it may be
used in other ways in other parts of the globe.

On the more general point, it might be interesting to conduct a gender
survey of those using this site. My impression is that the subject has
a greater appeal for males than females. Although many women may
have a short-term relationship with the subject, it would seem to be
more often men that develop a deeper or longer term interest.

I appreciate that gender politics is a "difficult" area and so perhaps
this subject should be moved to another part of the forum. I am not
casting any aspersions - just pondering on what the statistical data
might reveal if able to be collected.
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alanr555



Joined: 01 Aug 2005
Posts: 198
Location: Bideford Devon EX39

PostPosted: Sat Dec 29, 2007 3:29 am    Post subject: Reply with quote

TKiel wrote:

What is mentioned as the W-wing is named in honor of the first person from this forum who mentioned the pattern. It had been discussed on other forums earlier and named differently.


Thank you for the reference to an earlier explanation.
That explanation relies on the concept of a "strong"link
(a concept which I think that I understand).

Essentially I regard a strong link as one which constrains
a digit to being placed in one of two places. This is one
of the guiding principles of my Mandatory Pairs technique
but the concept extends beyond my use of recording the
strong links that occur within regions.

I accept that strong links can occur WITHIN triples and quartets
as well as in remote pairs and mutual reception cases (known
as twins in some SuDoku dialects). Wherever they occur, they
are based on the binary concept "if not here, then there" with
here and there being specific locations.

Thus the "non-algebraic" definition is developing as

"Where two cells anywhere in the grid contain just the same two
candidate digits and each of the two cells is in direct contact
(by line or region) with one or other of two other cells which
have a STRONG link based on one of the digits in the original
two cells, then
the digit in the original two cells that is NOT used to form the
strong link may be eliminated from any cell that is in direct
contact (by line or region) with BOTH of the two original cells."

supplemented by a preliminary definition

"The STRONG link between two cells is defined as one where the
two cells have a digit in common and that digit is absent from all
the other cells in any ONE column, row or region of which those
two cells are both members"

I appreciate that this MAY be overly simplistic in that there can be
strong links derived from other techniques but I suspect that those
other techniques may be used first to simplify the position before
attempting to apply the W-wing. Any pattern which depends upon
the SIMULTANEOUS application of W-wing and another technique
would be awesome indeed (in the sense of evoking a sense of
wonder and recognition of its marvellous qualities)!

Any discernment of errors in my understanding would be welcome.
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Marty R.



Joined: 12 Feb 2006
Posts: 5732
Location: Rochester, NY, USA

PostPosted: Sat Dec 29, 2007 5:02 am    Post subject: Reply with quote

Quote:
Quote:

Artificiality seems to be part of the whole thing, and adds to the fun,
what with kites, skyscrapers, Medusa, ocean-dwelling creatures, squirmbags, and the like. Wink Laughing


Clearly my education is lacking - but I will await publication of a
puzzle where the solution uses these techniques before I ask
anyone to elucidate.

Those are just a few of the terms; it can be mind-boggling.

As to gender, we have had a few women post to ask questions from time to time, but I'm not aware of any who are regulars. At least none of the regulars post with a clearly female name, although there are those with user names that are not given names and thus not gender-revealing. But it does seem that it appeals to men to a greater degree. I'd certainly welcome more diversity here.
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