-- Now we are going to decode each record as User type.
type alias User =
    { id : String
    , name : String
    , age : Int
    , mail : Maybe String
    }


-- You define decoder with type `Decoder User`
userDecoder : Decoder User
userDecoder =
    succeed User
        |= field "id"
        |= field "name"
        |= int (field "age")
        |= optional (field "mail")


-- This is the source formed of CSV.
source : String
source =
    """
id,name,age,mail
1,John Smith,20,john@example.com
2,Jane Smith,19,
"""


-- Run decoder.
> CsvDecode.run userDecoder source
Ok
    [ { id = "1", name = "John Smith", age = 20, mail = Just "john@example.com" }
    , { id = "2", name = "Jane Smith", age = 19, mail = Nothing }
    ]