FA-71894 / Error-correcting codes / Member archive

Repetition decoder resolves ties to zero · case 04

Evenly split or fully erased blocks decode to 0 instead of unknown.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Decode an n-fold repetition code sent in contiguous blocks of n symbols; each received symbol is 0, 1 or None (erasure). Erasures do not vote. The bit is the majority of non-erased symbols; a tie (including an all-erased block) yields None. fixed_count counts non-erased symbols outvoted in decided blocks. A length that is not a multiple of n, or n < 1, returns None. Return [bits, fixed_count].

Why this case matters

Robust control channels repeat critical flags and must treat erased symbols differently from zeros.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression [[1, 0, null, null, 1, 1], 3]	`[[0, 1], 1]`	`[[null, 1], 0]`	Failed

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