Introduction_to_Haskell_2ed_source
Introduction_to_Haskell_2ed_source copied to clipboard
HaskellZhangSong
C12 StackCalc
在用GHC 8.6编译这个项目会报错
Calculator.hs:92:17: error: • No instance for (Fail.MonadFail Data.Functor.Identity.Identity) arising from a do statement with the failable pattern ‘Right top’
原因是 GHC 8.6 默认开启了MonadFailDesugaring extension，详见https://gitlab.haskell.org/ghc/ghc/wikis/migration/8.6#MonadFailDesugaringbydefault
用do语法糖来写的代码，现在都被desugar了
暂时的解决方案是：在用ghci load之前:set -XMonadFailDesugaring 或者在Main.hs 加上{-# LANGUAGE NoMonadFailDesugaring #-}
如果要 desugaring the pattern match应该怎么改代码？
