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
<manfred.lotz@arcor.de> wrote:
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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Michael Xavier
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