FA-70374 / GIS polygon topology / Member archive

Ring vertex cleaning with snapping tolerance: distance metric · case 04

Diagonal jitter survives cleaning while axis-aligned jitter is removed.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Input [ring, eps] where ring is an open or closed list of integer [x, y] positions and eps >= 0. Walk the ring and drop a position whose Chebyshev distance to the last KEPT position is <= eps. Then repeatedly drop trailing kept positions within eps of the first kept position. If fewer than 3 positions remain return None, else return the kept positions closed by repeating the first.

Why this case matters

Digitised boundaries carry jitter and duplicate clicks; cleaning must not let small steps accumulate into dropped corners or leave near-closing duplicates.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
control #10	`[[30, 78], [22, 36], [32, 33], [50, 13], [76, 40], [78, 38], [73, 49], [75, 47], [30, 78]]`	`[[30, 78], [22, 36], [32, 33], [50, 13], [76, 40], [73, 49], [30, 78]]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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