Question

我是haskell的新手，我正在创建一个我所关注的所有博客/网站的RSS源，就像新闻源一样，但是我遇到了障碍。

rssFeed :: Snap ()
rssFeed = 
    feed <- parseFeedString "https://news.ycombinator.com/rss"
    putStrLn (ppTopElement $ xmlFeed feed)

这是创建Feed的主要功能，但在编译时我会收到此错误

Resolving dependencies...
Configuring feedre-0.1...
Building feedre-0.1...
Preprocessing executable 'feedre' for feedre-0.1...
[1 of 1] Compiling Main             ( src/Main.hs, dist/build/feedre/feedre-tmp/Main.o )

src/Main.hs:26:14: parse error on input `<-'
Failed to install feedre-0.1
cabal: Error: some packages failed to install:
feedre-0.1 failed during the building phase. The exception was:
ExitFailure 1

Answer 1

我认为你只错过do：

rssFeed :: Snap ()
rssFeed = do
    feed <- parseFeedString "https://news.ycombinator.com/rss"
    putStrLn (ppTopElement $ xmlFeed feed)

因为<-来自do-notation。

我不知道Snap monad的外观如何，但我猜您liftIO可能需要putStrLn：

liftIO $ putStrLn (ppTopElement $ xmlFeed feed)

haskell feed库RSS不会解析字符串

1 个答案: