FA-67149 / Railway interlocking logic / Member archive

Train describer berth stepping: clash detection · case 04

Overwriting a description in an occupied berth goes unreported.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

A train describer has berths 0..n-1. interpose writes a headcode, cancel blanks a berth. step i moves the description from berth i to i+1 (or out of the area from the last berth, recorded in exited); stepping an empty berth carries the unknown description ????. Stepping onto a filled berth records a clash at the destination and the stepped description overwrites it. The source berth is always blanked.

Why this case matters

Interlocking logic decides whether trains may be given authority; a wrong decision at this point either grants unsafe movements or strands traffic.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: clash with the same headcode	`{"berths": [null, "1A01", null], "clashes": [], "exited": []}`	`{"berths": [null, "1A01", null], "clashes": [1], "exited": []}`	Failed

MEMBER ARCHIVE

The complete case is available to members.

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

Member access is invitation-based. Sign in with your invited account to inspect the sources.