Haskell：错误：解析输入“ else”上的错误

Question

avoidHookRule :: Int -> [Cards] -> Int
avoidHookRule initialBid hand = if decrementBid /= 0
                                    then
                                      decrementBid
                                    else
                                      if incrementBid <= length hand
                                          incrementBid
                                      else -- <- error occurs on this line 
                                          incrementBid - 2
                                where incrementBid = initialBid + 1
                                      decrementBid = initialBid - 1

正如标题所述，我的else语句出现错误。为什么会这样呢？我如何解决它？谢谢

Answer 1

if incrementBid <= length hand
    incrementBid
else -- <- error occurs on this line 
    incrementBid - 2

then不是可选的，并且在此块中丢失。