Chess invariants
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Chess invariants
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Re: Chess invariants
#2If you like this, you're probably gonna like this: https://en.wikipedia.org/wiki/Chessboard_complex
Re: Chess invariants
#3> Chess is a lot trickier than it looks. It has so many rules: castling, en passant, pawn promotion, pinning, the discovered check, and the deadlock case of stalemate.
Nit: Pinning and the discovered check are not really rules, but rather names of tactics.
Re: Chess invariants
#4> Chess is a lot trickier than it looks. It has so many rules: castling, en passant, pawn promotion, pinning, the discovered check, and the deadlock case of stalemate. Nit: Pinning and the discovered check are not really rules, but rather names of tactics.
Well, if a piece is pinned it's illegal to move it.
Rule 3.9.2: No piece can be moved that will either expose the king of the same colour to check or leave that king in check.
Re: Chess invariants
#5I can't wait to show this to my manager next time he asks why it's taking three weeks to build a simple CRUD app.
"Look, if this guys TLA+ logic struggles to model a 1,500-year-old game without crying over a French pawn-capture rule, you can't expect me to integrate Stripe billing without a few state invariant violations."
Re: Chess invariants
#6> Chess is a lot trickier than it looks. It has so many rules: castling, en passant, pawn promotion, pinning, the discovered check, and the deadlock case of stalemate. Nit: Pinning and the discovered check are not really rules, but rather names of tactics.
Well, if a piece is pinned it's illegal to move it. Rule 3.9.2: No piece can be moved that will either expose the king of the same colour to check or leave that king in check.
Unlike en-passant and castling, pinning and discovered checks are consequences of lower-level rules.
At the "Is this move legal?" level, they don't need unique rules of its own if the lower-level rules are specified correctly.
Re: Chess invariants
#7> Chess is a lot trickier than it looks. It has so many rules: castling, en passant, pawn promotion, pinning, the discovered check, and the deadlock case of stalemate. Nit: Pinning and the discovered check are not really rules, but rather names of tactics.
And discovered check means that it is not sufficient to check the position of the piece you have moved, you also need to check the position of other pieces to see whether there is a new check.
Re: Chess invariants
#8> Chess is a lot trickier than it looks. It has so many rules: castling, en passant, pawn promotion, pinning, the discovered check, and the deadlock case of stalemate. Nit: Pinning and the discovered check are not really rules, but rather names of tactics.
Well, if a piece is pinned it's illegal to move it. Rule 3.9.2: No piece can be moved that will either expose the king of the same colour to check or leave that king in check.
You can also pin a pawn to a queen, but the pawn can still legally move.
Re: Chess invariants
#9Earlier quoted context omitted.
Well, if a piece is pinned it's illegal to move it. Rule 3.9.2: No piece can be moved that will either expose the king of the same colour to check or leave that king in check.
Unlike en-passant and castling, pinning and discovered checks are consequences of lower-level rules. At the "Is this move legal?" level, they don't need unique rules of its own if the lower-level rules are specified correctly.
3.9.2: no piece can be moved if that exposes or leaves its own king in check.
Re: Chess invariants
#10> Chess is a lot trickier than it looks. It has so many rules: castling, en passant, pawn promotion, pinning, the discovered check, and the deadlock case of stalemate. Nit: Pinning and the discovered check are not really rules, but rather names of tactics.
Well, if a piece is pinned it's illegal to move it. Rule 3.9.2: No piece can be moved that will either expose the king of the same colour to check or leave that king in check.
The point is that, logically, the first part of that rule (“expose the king”) is implied by the second part (“leave that king”), so the first part is redundant. You could simplify the rule to:
No piece can be moved that will leave the king of the same color in check.