03 Nov '13 02:55>
Is it...
Or...
Position 1
Or...
Position 2
Originally posted by moonbusThis bishop could have left its original square and moved back, which would have created a path for the rook.
If White has Ps on h3, g2 & e2, then the White R has no path to e6 (the light-squared B blocks the R). Therefore the position with a P on h3 is not legal.
Originally posted by Paul LeggettI can't fault moonbus' reasoning, which leads to a sequence where the White e-pawn hasn't moved with the bishop on f1, still. Therefore, via the h-file is the only route for the h1 rook to get out, and thus the position with the pawn on g3 is correct.
This bishop could have left its original square and moved back, which would have created a path for the rook.
I'm not sure that we can even assume that the rook on e6 was the h1 rook, as both bishops could have moved and returned, the a1 rook could have gone to e6, and the h1 rook to a1.
That said, if we could show that the bishop on f1 has neve ...[text shortened]... h.
SG's condition is that the position needs to be legal, but it does not have to be logical.
Originally posted by Paul LeggettThere may indeed be multiple possible solutions, one of which involves pawn promotion. I accept that the White R on e6 might not be the original R from h1.
This bishop could have left its original square and moved back, which would have created a path for the rook.
I'm not sure that we can even assume that the rook on e6 was the h1 rook, as both bishops could have moved and returned, the a1 rook could have gone to e6, and the h1 rook to a1.
That said, if we could show that the bishop on f1 has neve ...[text shortened]... h.
SG's condition is that the position needs to be legal, but it does not have to be logical.
Originally posted by moonbusI don't think it is a prima facie situation, in that the burden of proof lies with showing that the bishop has not moved. If we can't prove that the bishop has never moved, then we can't assume the rook is on e6 illegally.
There may indeed be multiple possible solutions, one of which involves pawn promotion. I accept that the White R on e6 might not be the original R from h1.
Can you show us an alternate sequence of moves without a White P starting at e2? If not, that is prima facie evidence that White's Bf1 has not moved.
Originally posted by Paul LeggettI take your point regarding the question whether Bf1 has moved; lack of evidence is not evidence of a lack.
I don't think it is a prima facie situation, in that the burden of proof lies with showing that the bishop has not moved. If we can't prove that the bishop has never moved, then we can't assume the rook is on e6 illegally.
I am merely saying that the bishops's presence on f1 does not prove that the rook on e6 is there illegally. Perhaps it ...[text shortened]... ght now it is an assertion not supported by evidence. My issue was with the original statement.
Originally posted by moonbusThat seems very well-reasoned to me!
I take your point regarding the question whether Bf1 has moved; lack of evidence is not evidence of a lack.
My proposed solution makes some assumptions. A) That SG's OR is logically exclusive. That is, only position 1 is legal, or only position 2 is legal, but not both. B) That neither White rook is a promoted pawn. I have not assumed that only one soluti ...[text shortened]... this has any bearing on whether position 1 or position 2 is legal. Open for further discussion.
Originally posted by greenpawn34SOLV'D.
This is the legal one.
[fen]6N1/p2prppb/kP1nR3/3qp3/8/2K1p1P1/1P4P1/R1B2B2 b - - 0 1[/fen]
The H7 Bishop is a promoted piece.
The h7 pawn must have promoted on d1 to a Bishop.
All the other Black pawns can be accounted for.
The pawn on e3 is the Black c-pawn it came from d4 after the ep capture.
You cannot get a pawn from h7 to d4.
White has ...[text shortened]... out after hxg3.
I think that's it, but as always I've probably overlooked something obvious.