H. G. Muller wrote on Sun, Feb 14, 2021 02:13 PM EST:
The Man/King is not a simple leaper. That term is reserved for pieces where all moves are rotated or mirrorred versions of each other. So the King is definitely a compound.
Compounds can have subsets to, though. Which then can be compounds of subsets of simple leapers. So I don't think that we can require a piece must be one or the other. Subset merely is an extra qualification that can be applied to simple leapers and compound leapers alike. (Or to sliders, for that matter.)
So there doesn't seem anything wrong with saying Gold is a subset of the King. That is more true than just saying it is a compound, as it is really a compound of subsets. That the King is a compound should be considered common knowledge. King and Queen have special status in this respect, because they are orthocox Chess pieces, and people can be expected to know them. Betza notation expresses their moves as a single capital, K or Q, officially 'shorthand' for WF and RB.
The large Shogi variants have many pieces, and they are virtually all subsets of the Queen. (As oblique moves are virtually non-existent in Shogi.) Some are even subsets of the Rook or the King.
What I dislike about the term 'subset' is that it has a well-defined meaning, which would consider the R4 a subset of the Rook. It seems that we now want to deviate from this meaning, by not allowing it to describe range restrictions, but only complete absence of a move in a certain direction. I think that such a distortion of the meaning of well-known terms is inadvisable.
The Man/King is not a simple leaper. That term is reserved for pieces where all moves are rotated or mirrorred versions of each other. So the King is definitely a compound.
Compounds can have subsets to, though. Which then can be compounds of subsets of simple leapers. So I don't think that we can require a piece must be one or the other. Subset merely is an extra qualification that can be applied to simple leapers and compound leapers alike. (Or to sliders, for that matter.)
So there doesn't seem anything wrong with saying Gold is a subset of the King. That is more true than just saying it is a compound, as it is really a compound of subsets. That the King is a compound should be considered common knowledge. King and Queen have special status in this respect, because they are orthocox Chess pieces, and people can be expected to know them. Betza notation expresses their moves as a single capital, K or Q, officially 'shorthand' for WF and RB.
The large Shogi variants have many pieces, and they are virtually all subsets of the Queen. (As oblique moves are virtually non-existent in Shogi.) Some are even subsets of the Rook or the King.
What I dislike about the term 'subset' is that it has a well-defined meaning, which would consider the R4 a subset of the Rook. It seems that we now want to deviate from this meaning, by not allowing it to describe range restrictions, but only complete absence of a move in a certain direction. I think that such a distortion of the meaning of well-known terms is inadvisable.