blue wrote:These aren't "fish" in the usual sense, and so what to call them is debatable, but for another term, how about like "PE candidates in the covering rows (for digit 9)". It's kind of long to write, and something shorter would be nice. The word "fin" should not be used, however ... and not just "IMO".

What about just calling them PE candidates ?

-- with the idea being that they are "potential eliminations" for the JExocet pattern (rather than for a fish pattern).

The idea would be that as soon as you can prove that the target cells must contain a particular digit, it's PE candidates can be eliminated.

Blue.

Added: After making the addition to the previous post.

The "last line" that I refered to in that post, is the last line above.

To clarify the situtation: refering to the previous post ... it isn't so much that we know that "at least one"

target cell, must contain a particular digit, but instead that we know that a

base cell must contain a particular digit. In a way, knowledge of one, implies knowledge of the other, and so maybe I'm more concerned with the details than I should be.

The point I wanted to make, was this, though: When we have a JExocet (or an exocet, "in general"), then we (can say that) we know that candidates in the target cells for the same digit, are "

weakly linked". The logic behind that (in brief), is that if a base digit candidate were true in one target, then via a long deduction, it would need to be true in a base cell as well. Then since the base cells can see each other, and so, can't contain the same digit (in a solution), the other base cell (in any solution) would contain a different digit, and it would be forced (for the JExocet case, via the partial fish logic) into the second target cell ... eliminatiing the candidate for the original digit, in that cell.

Summarizing the paragraph above: candidates for the same base digit, in the target cells, are weakly linked (regardless of what we know about the presence of that digit in a base cell).

In order to make the kind of X-wing chain from the previous post, "work", though -- we need to know that the digit, definitely must appear in one of the base cells. At that point, we can eliminate the candidates for that digit, in the other cells in the box that contains the base cells -- in particular, in the cells in the S column. It's (only) at that point, that the X-wing chain (from the previous post) becomes valid.

So, to summarize a bit farther: what I said in the first part of this post -- that we can eliminate the PE candidates, once we know that a base digit, must occupy one of the

target cells -- is a bit of a stretch. More correct, is that once we know that a particular digit must occupy one of the

base cells -- and given that the candidates for that digit in the target cells, are weakly linked --

then we can eliminate the PE candidates, via the kind of X-wing chain that I presented. Again, however, once we know one fact (base or target), the other is implied.

A question then: has anyone ever used the fact that candidates for a base digit, in the target cells, are

weakly linked )regardless of what we know about whether the digit must occur in a base cell) ... to produce a "chain-based" elimination ?