FA-15135 / Numerics / Member archive
Factoradic permutation unrank: alphabet selection removal · case 05
The exact factoradic permutation unrank result violates the stated contract at alphabet selection removal.
Case contract
Input [n,r], n<=7 and 0<=r<n!; return lexicographic permutation of 0..n-1 at rank r.
Why this case matters
Exact discrete arithmetic with observable algorithmic state; no floating point approximation is used.
One recorded failure
Sample boundary fixtureThis sample comes from the broken implementation of a controlled reproducer.
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| explicit oracle 0 | [1, 1, 0] | [1, 2, 0] | Failed |
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