The New Sudoku Players' Forum

[Myth Jellies]

What I'm most concerned with is the use of - vs. = and how to read this in terms of "implies" or "implies NOT", etc.

I think the best way to read it is

= means that at least one of the elements on either side of the symbol must be true.

location =7= location means that a 7 must go in one of those locations

- means that at least one of the elements on either side of the symbol must be false

location -7- location means that a 7 cannot be placed in both of those locations

[Carcul]

Is there some place where this notation is explained?

Try here.

Carcul

[daj95376]

For example from Carcul's post:

[r9c6]-3-[r7c46]=3,8|2=[r8c2]-2-[r9c1]-7-[r9c8]-3-[r9c6]

Is there some place where this notation is explained? What I'm most concerned with is the use of - vs. = and how to read this in terms of "implies" or "implies NOT", etc.

Chain notation is spread over several message threads. Some chain types have their own variation. I created a note on the basic chain type from a post by Viggo where he commented on chain notation from ronk. Maybe my note will be of some help. (Basically, I'm repeating Myth Jellies reply.)

Code: Select all

[r9c8]=1=[r9c4]=2=[r8c4]-2-[r8c7]-4-[r9c8], => r9c8<>4

if r9c8 is not 1, then r9c4 is     1 "[r9c8]=1=[r9c4]"
if r9c4 is not 2, then r8c4 is     2 "         [r9c4]=2=[r8c4]"
if r8c4 is     2, then r8c7 is not 2 "                  [r8c4]-2-[r8c7]"
if r8c7 is     4, then r9c8 is not 4 "                           [r8c7]-4-[r9c8]"

You interpret the link statements like this:

Strong Link:  [cell_1]=a=[cell_2]   =>   if (cell_1 is not a) then (cell_2 is     a)
Weak   Link:  [cell_1]-a-[cell_2]   =>   if (cell_1 is     a) then (cell_2 is not a)


For my own use, I write the above chain as:

Code: Select all

4=[r9c8]=1=[r9c4]=2=[r8c4]-2-[r8c7]-4-[r9c8] => r9c8<>4


Although I don't recall reading it formally anywhere, it seems that most posted chains start with a strong link.

[Len]

If you chain saw your way thru this thing you find 1 will not work in r2c5 so r2c5=8. Then 1 will not work in r1c5 so r1c5=2 which cracks the puzzle.