FA-82366 / Chess move legality / Open access
Slider x-rays through an enemy piece · case 01
A rook facing an enemy pawn is offered the squares behind it, including the enemy king square.
ROOT CAUSE
The ray only stops at friendly pieces; after capturing it keeps walking.
VERIFIED REPAIR
Stop the ray at the first occupied square, adding it only when it holds an enemy piece.
Unsuccessful approach: Stopping without adding the square removes legitimate captures.
Case contract
Input: {"board", "from": square of a rook, bishop or queen}. Return the sorted pseudo-legal destinations: walk each ray until the edge; an empty square is added, an enemy piece is added and ends the ray, a friendly piece ends the ray without being added.
Why this case matters
Move validators gate every move in engines, servers and arbiters; accepting an illegal move or rejecting a legal one corrupts the game record.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(x):
b=x['board']; sq=x['from']; p=b[sq]
f,r=ord(sq[0])-97,int(sq[1])-1
dirs={'r':[(1,0),(-1,0),(0,1),(0,-1)],'b':[(1,1),(1,-1),(-1,1),(-1,-1)]}
dirs['q']=dirs['r']+dirs['b']
out=[]
for df,dr in dirs[p.lower()]:
cf,cr=f+df,r+dr
while 0<=cf<8 and 0<=cr<8:
t=chr(97+cf)+str(cr+1)
occ=b.get(t)
if occ is None:
out.append(t)
else:
if occ.isupper()!=p.isupper(): out.append(t)
else: break
cf+=df; cr+=dr
return sorted(out)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('rook blocked by enemy', {'board': {'a1': 'R', 'a3': 'p', 'c1': 'N'}, 'from': 'a1'},
['a2', 'a3', 'b1']),
('rook behind enemy',
{'board': {'b4': 'b', 'd4': 'R', 'd6': 'p', 'd8': 'k', 'f4': 'P'}, 'from': 'd4'},
['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('queen open', {'board': {'a5': 'R', 'd5': 'q', 'd7': 'p', 'g8': 'P'}, 'from': 'd5'},
['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5',
'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5']),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6'])],
[('rook behind enemy',
{'board': {'b4': 'b', 'd4': 'R', 'd6': 'p', 'd8': 'k', 'f4': 'P'}, 'from': 'd4'},
['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('queen open', {'board': {'a5': 'R', 'd5': 'q', 'd7': 'p', 'g8': 'P'}, 'from': 'd5'},
['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5',
'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5']),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6']),
('bishop sw ray', {'board': {'c2': 'r', 'f5': 'B', 'h7': 'p'}, 'from': 'f5'},
['c2', 'c8', 'd3', 'd7', 'e4', 'e6', 'g4', 'g6', 'h3', 'h7'])],
[('rook blocked by enemy', {'board': {'a1': 'R', 'a3': 'p', 'c1': 'N'}, 'from': 'a1'},
['a2', 'a3', 'b1']),
('rook behind enemy',
{'board': {'b4': 'b', 'd4': 'R', 'd6': 'p', 'd8': 'k', 'f4': 'P'}, 'from': 'd4'},
['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6']),
('bishop sw ray', {'board': {'c2': 'r', 'f5': 'B', 'h7': 'p'}, 'from': 'f5'},
['c2', 'c8', 'd3', 'd7', 'e4', 'e6', 'g4', 'g6', 'h3', 'h7'])],
[('rook blocked by enemy', {'board': {'a1': 'R', 'a3': 'p', 'c1': 'N'}, 'from': 'a1'},
['a2', 'a3', 'b1']),
('rook behind enemy',
{'board': {'b4': 'b', 'd4': 'R', 'd6': 'p', 'd8': 'k', 'f4': 'P'}, 'from': 'd4'},
['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('queen open', {'board': {'a5': 'R', 'd5': 'q', 'd7': 'p', 'g8': 'P'}, 'from': 'd5'},
['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5',
'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5']),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6'])],
[('rook blocked by enemy', {'board': {'a1': 'R', 'a3': 'p', 'c1': 'N'}, 'from': 'a1'},
['a2', 'a3', 'b1']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('queen open', {'board': {'a5': 'R', 'd5': 'q', 'd7': 'p', 'g8': 'P'}, 'from': 'd5'},
['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5',
'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5']),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6']),
('bishop sw ray', {'board': {'c2': 'r', 'f5': 'B', 'h7': 'p'}, 'from': 'f5'},
['c2', 'c8', 'd3', 'd7', 'e4', 'e6', 'g4', 'g6', 'h3', 'h7'])]]
for label, args, expected in fixtures[N-1]:
try:
actual = solve(args)
except Exception as exc:
actual = 'error:' + type(exc).__name__
check(label, actual, expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| rook blocked by enemy | ['a2', 'a3', 'a4', 'a5', 'a6', 'a7', 'a8', 'b1'] | ['a2', 'a3', 'b1'] | Failed |
| rook behind enemy | ['a4', 'b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'd7', 'd8', 'e4'] | ['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4'] | Failed |
| bishop corner | ['a8', 'b7', 'c6', 'd5', 'e4', 'f3', 'g2'] | ['e4', 'f3', 'g2'] | Failed |
| bishop centre | ['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1', 'g7', 'h8'] | ['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1'] | Failed |
| queen boxed | [] | [] | Passed |
| queen open | ['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5', 'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5'] | ['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5', 'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5'] | Passed |
| black rook top edge | ['f8', 'g8', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'h7'] | ['f8', 'g8', 'h5', 'h6', 'h7'] | Failed |
| queen along diagonal capture | ['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6'] | ['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6'] | Passed |
SHA-256 / 65f407177527a1fd591d595940724da20bbc3d1c4e77f7eb8d217d94ab83f83c
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(x):
b=x['board']; sq=x['from']; p=b[sq]
f,r=ord(sq[0])-97,int(sq[1])-1
dirs={'r':[(1,0),(-1,0),(0,1),(0,-1)],'b':[(1,1),(1,-1),(-1,1),(-1,-1)]}
dirs['q']=dirs['r']+dirs['b']
out=[]
for df,dr in dirs[p.lower()]:
cf,cr=f+df,r+dr
while 0<=cf<8 and 0<=cr<8:
t=chr(97+cf)+str(cr+1)
occ=b.get(t)
if occ is None:
out.append(t)
else:
pass
break
cf+=df; cr+=dr
return sorted(out)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('rook blocked by enemy', {'board': {'a1': 'R', 'a3': 'p', 'c1': 'N'}, 'from': 'a1'},
['a2', 'a3', 'b1']),
('rook behind enemy',
{'board': {'b4': 'b', 'd4': 'R', 'd6': 'p', 'd8': 'k', 'f4': 'P'}, 'from': 'd4'},
['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('queen open', {'board': {'a5': 'R', 'd5': 'q', 'd7': 'p', 'g8': 'P'}, 'from': 'd5'},
['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5',
'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5']),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6'])],
[('rook behind enemy',
{'board': {'b4': 'b', 'd4': 'R', 'd6': 'p', 'd8': 'k', 'f4': 'P'}, 'from': 'd4'},
['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('queen open', {'board': {'a5': 'R', 'd5': 'q', 'd7': 'p', 'g8': 'P'}, 'from': 'd5'},
['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5',
'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5']),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6']),
('bishop sw ray', {'board': {'c2': 'r', 'f5': 'B', 'h7': 'p'}, 'from': 'f5'},
['c2', 'c8', 'd3', 'd7', 'e4', 'e6', 'g4', 'g6', 'h3', 'h7'])],
[('rook blocked by enemy', {'board': {'a1': 'R', 'a3': 'p', 'c1': 'N'}, 'from': 'a1'},
['a2', 'a3', 'b1']),
('rook behind enemy',
{'board': {'b4': 'b', 'd4': 'R', 'd6': 'p', 'd8': 'k', 'f4': 'P'}, 'from': 'd4'},
['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6']),
('bishop sw ray', {'board': {'c2': 'r', 'f5': 'B', 'h7': 'p'}, 'from': 'f5'},
['c2', 'c8', 'd3', 'd7', 'e4', 'e6', 'g4', 'g6', 'h3', 'h7'])],
[('rook blocked by enemy', {'board': {'a1': 'R', 'a3': 'p', 'c1': 'N'}, 'from': 'a1'},
['a2', 'a3', 'b1']),
('rook behind enemy',
{'board': {'b4': 'b', 'd4': 'R', 'd6': 'p', 'd8': 'k', 'f4': 'P'}, 'from': 'd4'},
['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('queen open', {'board': {'a5': 'R', 'd5': 'q', 'd7': 'p', 'g8': 'P'}, 'from': 'd5'},
['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5',
'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5']),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6'])],
[('rook blocked by enemy', {'board': {'a1': 'R', 'a3': 'p', 'c1': 'N'}, 'from': 'a1'},
['a2', 'a3', 'b1']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('queen open', {'board': {'a5': 'R', 'd5': 'q', 'd7': 'p', 'g8': 'P'}, 'from': 'd5'},
['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5',
'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5']),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6']),
('bishop sw ray', {'board': {'c2': 'r', 'f5': 'B', 'h7': 'p'}, 'from': 'f5'},
['c2', 'c8', 'd3', 'd7', 'e4', 'e6', 'g4', 'g6', 'h3', 'h7'])]]
for label, args, expected in fixtures[N-1]:
try:
actual = solve(args)
except Exception as exc:
actual = 'error:' + type(exc).__name__
check(label, actual, expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| rook blocked by enemy | ['a2', 'b1'] | ['a2', 'a3', 'b1'] | Failed |
| rook behind enemy | ['c4', 'd1', 'd2', 'd3', 'd5', 'e4'] | ['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4'] | Failed |
| bishop corner | ['f3', 'g2'] | ['e4', 'f3', 'g2'] | Failed |
| bishop centre | ['c3', 'c5', 'e3', 'e5', 'f2'] | ['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1'] | Failed |
| queen boxed | [] | [] | Passed |
| queen open | ['a2', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5', 'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'h1', 'h5'] | ['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5', 'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5'] | Failed |
| black rook top edge | ['f8', 'g8', 'h6', 'h7'] | ['f8', 'g8', 'h5', 'h6', 'h7'] | Failed |
| queen along diagonal capture | ['a1', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1'] | ['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6'] | Failed |
SHA-256 / 5c392c9366cb424f538c27a1e66c89e11f1a866c187b08c3e107a155b79eddd6
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(x):
b=x['board']; sq=x['from']; p=b[sq]
f,r=ord(sq[0])-97,int(sq[1])-1
dirs={'r':[(1,0),(-1,0),(0,1),(0,-1)],'b':[(1,1),(1,-1),(-1,1),(-1,-1)]}
dirs['q']=dirs['r']+dirs['b']
out=[]
for df,dr in dirs[p.lower()]:
cf,cr=f+df,r+dr
while 0<=cf<8 and 0<=cr<8:
t=chr(97+cf)+str(cr+1)
occ=b.get(t)
if occ is None:
out.append(t)
else:
if occ.isupper()!=p.isupper(): out.append(t)
break
cf+=df; cr+=dr
return sorted(out)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('rook blocked by enemy', {'board': {'a1': 'R', 'a3': 'p', 'c1': 'N'}, 'from': 'a1'},
['a2', 'a3', 'b1']),
('rook behind enemy',
{'board': {'b4': 'b', 'd4': 'R', 'd6': 'p', 'd8': 'k', 'f4': 'P'}, 'from': 'd4'},
['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('queen open', {'board': {'a5': 'R', 'd5': 'q', 'd7': 'p', 'g8': 'P'}, 'from': 'd5'},
['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5',
'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5']),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6'])],
[('rook behind enemy',
{'board': {'b4': 'b', 'd4': 'R', 'd6': 'p', 'd8': 'k', 'f4': 'P'}, 'from': 'd4'},
['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('queen open', {'board': {'a5': 'R', 'd5': 'q', 'd7': 'p', 'g8': 'P'}, 'from': 'd5'},
['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5',
'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5']),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6']),
('bishop sw ray', {'board': {'c2': 'r', 'f5': 'B', 'h7': 'p'}, 'from': 'f5'},
['c2', 'c8', 'd3', 'd7', 'e4', 'e6', 'g4', 'g6', 'h3', 'h7'])],
[('rook blocked by enemy', {'board': {'a1': 'R', 'a3': 'p', 'c1': 'N'}, 'from': 'a1'},
['a2', 'a3', 'b1']),
('rook behind enemy',
{'board': {'b4': 'b', 'd4': 'R', 'd6': 'p', 'd8': 'k', 'f4': 'P'}, 'from': 'd4'},
['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6']),
('bishop sw ray', {'board': {'c2': 'r', 'f5': 'B', 'h7': 'p'}, 'from': 'f5'},
['c2', 'c8', 'd3', 'd7', 'e4', 'e6', 'g4', 'g6', 'h3', 'h7'])],
[('rook blocked by enemy', {'board': {'a1': 'R', 'a3': 'p', 'c1': 'N'}, 'from': 'a1'},
['a2', 'a3', 'b1']),
('rook behind enemy',
{'board': {'b4': 'b', 'd4': 'R', 'd6': 'p', 'd8': 'k', 'f4': 'P'}, 'from': 'd4'},
['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('queen open', {'board': {'a5': 'R', 'd5': 'q', 'd7': 'p', 'g8': 'P'}, 'from': 'd5'},
['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5',
'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5']),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6'])],
[('rook blocked by enemy', {'board': {'a1': 'R', 'a3': 'p', 'c1': 'N'}, 'from': 'a1'},
['a2', 'a3', 'b1']),
('bishop corner', {'board': {'e4': 'P', 'h1': 'b'}, 'from': 'h1'}, ['e4', 'f3', 'g2']),
('bishop centre',
{'board': {'b2': 'P', 'b6': 'P', 'd4': 'B', 'f6': 'n', 'g1': 'q'}, 'from': 'd4'},
['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1']),
('queen boxed',
{'board': {'d1': 'K', 'd2': 'P', 'e1': 'Q', 'e2': 'P', 'f1': 'B', 'f2': 'P'}, 'from': 'e1'},
[]),
('queen open', {'board': {'a5': 'R', 'd5': 'q', 'd7': 'p', 'g8': 'P'}, 'from': 'd5'},
['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5',
'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5']),
('black rook top edge', {'board': {'e8': 'k', 'h5': 'P', 'h8': 'r'}, 'from': 'h8'},
['f8', 'g8', 'h5', 'h6', 'h7']),
('queen along diagonal capture',
{'board': {'a3': 'n', 'c1': 'Q', 'c3': 'P', 'h6': 'r'}, 'from': 'c1'},
['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6']),
('bishop sw ray', {'board': {'c2': 'r', 'f5': 'B', 'h7': 'p'}, 'from': 'f5'},
['c2', 'c8', 'd3', 'd7', 'e4', 'e6', 'g4', 'g6', 'h3', 'h7'])]]
for label, args, expected in fixtures[N-1]:
try:
actual = solve(args)
except Exception as exc:
actual = 'error:' + type(exc).__name__
check(label, actual, expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| rook blocked by enemy | ['a2', 'a3', 'b1'] | ['a2', 'a3', 'b1'] | Passed |
| rook behind enemy | ['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4'] | ['b4', 'c4', 'd1', 'd2', 'd3', 'd5', 'd6', 'e4'] | Passed |
| bishop corner | ['e4', 'f3', 'g2'] | ['e4', 'f3', 'g2'] | Passed |
| bishop centre | ['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1'] | ['c3', 'c5', 'e3', 'e5', 'f2', 'f6', 'g1'] | Passed |
| queen boxed | [] | [] | Passed |
| queen open | ['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5', 'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5'] | ['a2', 'a5', 'a8', 'b3', 'b5', 'b7', 'c4', 'c5', 'c6', 'd1', 'd2', 'd3', 'd4', 'd6', 'e4', 'e5', 'e6', 'f3', 'f5', 'f7', 'g2', 'g5', 'g8', 'h1', 'h5'] | Passed |
| black rook top edge | ['f8', 'g8', 'h5', 'h6', 'h7'] | ['f8', 'g8', 'h5', 'h6', 'h7'] | Passed |
| queen along diagonal capture | ['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6'] | ['a1', 'a3', 'b1', 'b2', 'c2', 'd1', 'd2', 'e1', 'e3', 'f1', 'f4', 'g1', 'g5', 'h1', 'h6'] | Passed |
SHA-256 / 241365503d4af9a5fa15bb896aaaf6ed5b65dea5a6a709cb1c9569d53ff8af2c
Verification & scope
A deterministic toy model with an explicitly stated contract; boards are {square: piece} with white upper-case and black lower-case pieces; no claim of full FIDE Laws conformance. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.
Observations recorded using Python 3.12.14 at 2026-09-29T14:50:11.459962+00:00.
Case digest / b63e765729088e8f96f59102695a6618089ea325190e6445574494ddb928fe0f