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Marty R.
Joined: 12 Feb 2006 Posts: 5215 Location: Rochester, NY, USA

Posted: Sat Feb 02, 2008 12:38 am Post subject: 


I only went two days this time. Can an inference be made based on an assumption of true in two or more cells? Consider these two cells in a line:
23g 2g34
Can we say that if 2g3g are both true, then the 4 can be inferred, thus creating a wrap? Seems too easy.
Or this:
38g 35g 158
Can we infer the 1 assuming that the 5g8g are both true? 

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Asellus
Joined: 05 Jun 2007 Posts: 865 Location: Sonoma County, CA, USA

Posted: Sat Feb 02, 2008 7:02 am Post subject: 


Marty R. wrote:  Can an inference be made based on an assumption of true in two or more cells? 
Yes, but...
In your first example, I don't see that there is any inference about the <4> in those two cells. We only know that the <4> is false if G is true (since in that case the cell must be <2>). But, that isn't very helpful. I certainly can't see a "wrap."
However, if that <4> were strongly linked to another <4> that already shared a cell with a "g" value, then you would have a wrap (since G would eliminate all <4>s in that house).
In the second example, we can infer that the <1> is "g", but not that it is true. In other words, if G is true, then the third cell must be <1>, hence, it can be colored "g".
I hope that is clear. 

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Marty R.
Joined: 12 Feb 2006 Posts: 5215 Location: Rochester, NY, USA

Posted: Sat Feb 02, 2008 4:16 pm Post subject: 


A,
Thanks, I hope for the last time.
I wasn't thinking very clearly when I presented my first example. How can you infer a cell is "x" if you assume it's "y'"? 

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Marty R.
Joined: 12 Feb 2006 Posts: 5215 Location: Rochester, NY, USA

Posted: Thu Feb 21, 2008 4:29 pm Post subject: 


Consider the following partial grid with madeup numbers just to illustrate the point:
Code:  ++++
 . . .  . . .  49g . . 
 . . .  . . .  139 . . 
 . . .  . . .  13 . . 
++++
 . . .  . . .  17 . . 
 . . .  . . .  . 69g . 
 . . .  . . .  . . . 
++++
 . . .  . . .  . . . 
 . . .  . . .  . . . 
 . . .  . . .  . . . 
++++

The 9g in box 6 has inferred the 9g in box 3. The latter 9g infers a naked 13 pair just below it. Is this a legitimate trap whereby r4c7 can be solved for 7? I'm used to my traps coming from little r's and g's.
Or is all we can do is mark the 7 with a "g"?
(First question in 20 days). 

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Asellus
Joined: 05 Jun 2007 Posts: 865 Location: Sonoma County, CA, USA

Posted: Fri Feb 22, 2008 12:02 am Post subject: 


Marty wrote:  Is this a legitimate trap whereby r4c7 can be solved for 7? ... Or is all we can do is mark the 7 with a "g"? 
All you can do is mark the 7 with a "g". The <1> can only be removed if it can "see" a red <1> somewhere.
[Edit to remove unnecessary comment.] 

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Marty R.
Joined: 12 Feb 2006 Posts: 5215 Location: Rochester, NY, USA

Posted: Fri Feb 22, 2008 1:19 am Post subject: 


As always, thanks. 

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Marty R.
Joined: 12 Feb 2006 Posts: 5215 Location: Rochester, NY, USA

Posted: Mon Mar 31, 2008 12:35 am Post subject: 


Code:  ++++
 . . .  . . .  . . . 
 . . .  . . .  . 4a8 . 
 . . .  . . .  . . . 
++++
 . . .  . . .  . . . 
 . . .  . . .  . 36b . 
 . . .  . . .  . . . 
++++
 . . .  . . .  . . . 
 . . .  . . .  . . . 
 . . .  . . .  . 469 . 
++++ 
The actual values shown are just for illustration. If I infer from the 4a, then r9c8 = 69. If I infer from the 6b, then r9c8 = 49. The 9 is there based on inferences from both a and b, so I placed it. Valid or did I just get lucky this one time? 

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Asellus
Joined: 05 Jun 2007 Posts: 865 Location: Sonoma County, CA, USA

Posted: Tue Apr 01, 2008 8:37 pm Post subject: 


Marty wrote:  Valid or did I just get lucky this one time? 
I believe that was luck. I don't see it as a valid placement. All you know is that r9c8 is either {69} or it is {49}. <4> and <6> are still possibilities. 

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Marty R.
Joined: 12 Feb 2006 Posts: 5215 Location: Rochester, NY, USA

Posted: Tue Apr 01, 2008 9:22 pm Post subject: 


As always, thanks. I guess I'll avoid that type of thing in the future. But I do understand what you're saying. 

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