The New Sudoku Players' Forum

[Glyn]

evert I think you may find this useful The Ultimate FISH Guide. Only vanilla are considered there but the concepts of base and cover sets is illustrated.

[tarek]

As Glyn mentioned, the definitions in the guide (which need some updates) are versatile enough to cover all variants.

To catch all possible fish, you need to consider constriant groups in your base and/or your cover groups ...

You have alos to look at the overlapping puzzles as 1 huge puzzle with overlaping constriant groups.

tarek

[Pat]

I think a definition of Fish could be as follows:

1. There are n different groups g(i) (i = 1..n).
2. A certain digit k has n different possible placements in each of the groups g(i).
3. None of these cells occur in more then one of the groups g(i).
4. There are also n different groups h(j) (j = 1..n).
5. Each group h(j) contains exactly one of the cells from each group g(i) where digit k can be placed.
6. Each placement for k in one of the groups g(i) occurs in exactly one of the groups h(j).

In this situation: k can be excluded from every cell in a group h(j), that does not occur in any of the groups g(i).

I wonder if this definition is both minimal and sufficient.
Sufficient in the sense that the exclusion of k is justified.
Minimal in the sense that all conditions 1 to 6 are necessary - otherwise the exclusion of k is not justified.

hi evert

see the fish definition (2007.Oct.2, on page 22 of "The Ultimate FISH Guide")

it does allow for possible overlap within the "base",
also for possible overlap within the "cover"