我如何将它变成 Setter？

Question

setOwner :: File -> User -> File
setOwner f o = f & ownerID .~ (o ^. User.uid)

如何将其变成 Setter？

我不能把它做成镜头因为getUser :: UserID -> IO User是一个不纯的函数。

Answer 1

我刚刚意识到我之前的回答是错误的。哎呀！

给你：

ownerS :: Setter File File () User
ownerS = sets (\f file -> setOwner file (f ()))

How do I turn this into a Setter?