如何将值打印/编码到Dhall

Question

{-# LANGUAGE DeriveGeneric     #-}
{-# LANGUAGE OverloadedStrings #-}
import Dhall
data Example = Example { foo :: Natural, bar :: Vector Double }
deriving (Generic, Show)
instance Interpret Example
main :: IO ()
main = do
putStrLn "Hello, Haskell!"
x <- input auto "./example.dhall"
print (x :: Example)

在上面的例子中，我如何将Example编码为dhall值，因此本质上是Example -> String类型的函数？在haddocks中似乎找不到任何关于打印/编码的引用。

Answer 1

这就是如何将Haskell值漂亮地打印为等效的Dhall表达式：

{-# LANGUAGE DeriveGeneric     #-}
{-# LANGUAGE DeriveAnyClass    #-}
{-# LANGUAGE OverloadedStrings #-}
import Dhall (FromDhall, Natural, ToDhall, Vector)
import Dhall.Pretty (CharacterSet(..))
import GHC.Generics (Generic)
import qualified Data.Text.Prettyprint.Doc.Render.Text as Prettyprint.Text
import qualified Dhall
import qualified Dhall.Pretty
import qualified Dhall.Core
data Example = Example { foo :: Natural, bar :: Vector Double }
deriving (FromDhall, Generic, Show, ToDhall)
main :: IO ()
main = do
x <- Dhall.input Dhall.auto "./example.dhall"
let expression = Dhall.embed Dhall.inject (x :: Example)
let doc = Dhall.Pretty.prettyCharacterSet Unicode expression
Prettyprint.Text.putDoc doc