Credence.Rule.NoSortForTopKReduce
(credence v0.3.1)
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Detects inefficient patterns where a full sort is performed only to
retrieve a small number of elements (top-k) that cannot be reduced to
a single Enum.min/1 or Enum.max/1 call.
Sorting an entire collection is O(n log n). When only a few elements
are needed, a single-pass O(n) approach using Enum.reduce/3 is
both faster and clearer in intent.
Flagged patterns
| Pattern | Suggested replacement |
|---|---|
Enum.sort/1 |> Enum.take(k) for k > 1 | Enum.reduce/3 (track top k) |
Enum.sort/1 |> Enum.at(1) | Enum.reduce/3 (track top two) |
| (same patterns with Enum.reverse() before the terminal step) ||
These patterns are not automatically fixable because the correct
replacement depends on the desired sort direction and requires a
multi-step Enum.reduce/3 or min-heap approach.
Bad
Enum.sort(list) |> Enum.take(5)
Enum.sort(list) |> Enum.at(1)Good
# Use Enum.reduce/3 to track the top-k elements in one pass