小编Diy*_*aev的帖子

尝试使用"堆栈构建"构建:

module Main where


analyzeGold :: Int -> String
analyzeGold standard =
  if | standard == 999 -> "Wow! 999 standard!"
     | standard == 750 -> "Great! 750 standard."
     | standard == 585 -> "Not bad! 585 standard."
     | otherwise -> "I don't know such a standard..."

main :: IO ()
main = do
  putStrLn (analyzeGold 999)

我得到了:

    Multi-way if-expressions need MultiWayIf turned on
  |
6 |   if | standard == 999 -> "Wow! 999 standard!"
  |   ^^

怎么解决？

堆栈1.7.1,GHC …