Credence.Pattern.PreferCountsForLength (credence v0.8.0)

Detects length(String.codepoints(string)) when a counts map from Enum.frequencies/1 on the same codepoints already exists.

String.codepoints/1 traverses the string once for Enum.frequencies/1 and a second time for length/1. Derive n from the existing counts map via Enum.sum(Map.values(counts)) to avoid the redundant traversal.

Bad

counts = string |> String.codepoints() |> Enum.frequencies()
n = length(String.codepoints(string))

Good

counts = string |> String.codepoints() |> Enum.frequencies()
n = Enum.sum(Map.values(counts))