Some random elm code to process a large list...

myfile.elm

convertRecordsTask : Task Http.Error (List (List String)) -> Task Http.Error (List TrajectoryPoint)
convertRecordsTask task =
    Task.map convertRecords task


convertRecords : List (List String) -> List TrajectoryPoint
convertRecords records =
    List.take 10000 records
        |> List.map convertRecord


convertRecord : List String -> TrajectoryPoint
convertRecord list =
    case list of
        sessionId :: orderId :: longitude :: latitude :: _ :: velocity :: timeOfOccurrence :: _ ->
            { sessionId = Result.withDefault 0 (String.toInt sessionId)
            , latitude = Result.withDefault 0.0 (String.toFloat latitude)
            , longitude = Result.withDefault 0.0 (String.toFloat longitude)
            , velocity = Result.withDefault 0.0 (String.toFloat velocity)
            , timeOfOccurrence = Result.withDefault 0.0 (String.toFloat timeOfOccurrence)
            }

        _ ->
            { sessionId = 0
            , latitude = 0.0
            , longitude = 0.0
            , velocity = 0.0
            , timeOfOccurrence = 0.0
            }


loadTrajectories : String -> Task Http.Error (List TrajectoryPoint)
loadTrajectories path =
    CsvLoader.loadAndParseCsv path
        |> convertRecordsTask