FA-94429 / Exam timetabling constraints / Member archive

Repeated enrolment rows multiply proximity pairs · case 04

A duplicated enrolment doubles the cost of every pair involving that exam.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

enrol [student, exam] rows (may repeat) and exam periods. For each student, each pair of distinct exams d = 1..5 periods apart costs 2^(5-d). Return [total, number of students, total/students as a reduced fraction string].

Why this case matters

The Carter proximity cost is the standard exam-timetabling quality measure; each piece has a known implementation pitfall.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: distinct exams 1	`[72, 2, "36"]`	`[40, 2, "20"]`	Failed

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