1
我試圖使用expression quotation, 寫一個聲明,無論我嘗試編譯器上的模板與下面這樣的消息:如何在表達式引用中編寫模式拼接?
Parse error in pattern: $pattern
下面是一個例子:
{-# LANGUAGE TemplateHaskell, QuasiQuotes #-}
import Language.Haskell.TH
data A = A Int Int
decl :: DecsQ
decl = [d|
instance Show A where
show $pattern = undefined
|]
where
pattern = conP (mkName "A") $ map varP $ map mkName $ ["a", "b"]