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signature SCORE = sig
val score: int * real * (string -> int option) * real * string -> real
end
structure Score :> SCORE = struct
fun |> (x, f) = f x
infix |>
fun addCount (hitsum, fcount, gcount, totalWords) =
Kahan.add (hitsum, Real.fromInt fcount * Math.ln (Real.fromInt gcount / totalWords))
fun addNmer (totalWords, getGenomeCount) (nmer, ref fcount, (misses, anyhits, hitsum)) =
case getGenomeCount nmer of
NONE => (misses + 1, anyhits, hitsum)
| SOME gcount => (
misses, true
, addCount (hitsum, fcount, gcount, totalWords)
)
fun score (order, missConstant, getGenomeCount, totalWords, fragment) =
let
val add = addNmer (totalWords, getGenomeCount)
val seed = (0, false, Kahan.zero)
val (misses, anyhits, hitsum) =
Nmer.count (order, fragment) |> HashTable.foldi add seed
in
if anyhits then
Kahan.add (hitsum, Math.ln missConstant * Real.fromInt misses)
|> Kahan.sum
else Real.negInf
end
end
|
