Re: [Haskell-cafe] Representing record subtypes, sort of.

Karl Voelker writes:

{-# LANGUAGE DataKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE KindSignatures #-} module FS where

type Date = String

data FileKind = FILE | FOLDER

data Entry (k :: FileKind) where File :: String -> Date -> Int -> Entry FILE Folder :: String -> String -> Entry FOLDER

This is a little beyond my Haskell knowledge. What would the function signatures look like? Here are my guesses: listFolder :: Path -> [Entry ?] createFolder :: Path -> Entry FOLDER createFile :: Path -> Entry FOLDER Also, lets say I wanted to just get the "id" fields from a list of `Entry` values. Can someone help me fill in the blanks here? l :: [Entry ?] let ids = map (?) l