我有以下基于csv-conduit的简单功能，它正在为#foo s调用自定义catMaybes实现。
Vector如果我用retrieveSmaXtec :: IO (Vector SxRecord)
retrieveSmaXtec = do
rows <- sourceFile "unordered.csv"
.| intoCSV defCSVSettings
.| sinkVector
& runConduitRes
putStrLn $ show $ size rows -- DEBUG
putStrLn $ show $ size $ (fmap fromRow rows) -- DEBUG
rows & fmap fromRow & catMaybes & return
删除了两行，则所有类型都会检查，尽管代码似乎确实存在一些问题-尽管单元测试表明putStrLn正常工作，但我似乎仍然得到当我知道我不应该返回空向量时。我之所以提及，只是因为它可能相关。我的实际问题是，为什么在添加fromRow调用时出现错误：
putStrLn 更新：正如评论中所暗示的那样，src/FDS/Data/SmaXtec.hs:64:25: error:
* Couldn't match type `Map k0 (Maybe SxRecord)'
with `Vector (Maybe SxRecord)'
Expected type: Map k0 (Maybe SxRecord) -> Vector SxRecord
Actual type: Vector (Maybe SxRecord) -> Vector SxRecord
* In the second argument of `(&)', namely `catMaybes'
In the first argument of `(&)', namely
`rows & fmap fromRow & catMaybes'
In a stmt of a 'do' block: rows & fmap fromRow & catMaybes & return
* Relevant bindings include
rows :: Map k0 (MapRow Text)
(bound at src/FDS/Data/SmaXtec.hs:58:3)
|
64 | rows & fmap fromRow & catMaybes & return
| ^^^^^^^^^
不是我想要的功能。我需要size。