I believe let when you're in do notation is for pure functions. Since c is
IO (String String), I think what you might try is:
c <- getXmlContent e
k <- fst c
v <- snd c
Or even better, use pattern matching:
(k, v) <- getXmlContent e
Someone please step in if I'm misrepresenting how it's done.
On Wed, May 11, 2011 at 11:05 AM, Manfred Lotz
Hi there, I've got a problem creating a map.
I have a list of dataset names and adding those dataset names into a map works fine like this:
<----------------------------snip--------------------------------> module Main where
import Data.List import qualified Data.Map as M
insertRec :: M.Map String String -> String -> M.Map String String insertRec m e = let f = M.lookup e m in if f == Nothing then M.insert e "bla" m else m
createMap :: [String] -> M.Map String String createMap lst = let m = M.empty in foldl' insertRec m lst
main :: IO () main = do let xmlfiles = [ "a.xml","f.xml"] let ht = createMap xmlfiles print ht <----------------------------snap-------------------------------->
However, actually I want to parse the xml files and adding content into the map.
For this I have a function getXmlContent :: FilePath -> IO (String,String)
and would like to do something like this:
<----------------------------snip--------------------------------> insertRec m e = do c <- getXmlContent e let k = fst c let v = snd c M.insert k v m <----------------------------snap-------------------------------->
Unfortunately, this doesn't work because of IO. I have no glue how to get this done.
Any help appreciated.
-- Thanks, Manfred
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