Having problems with a Haskell script. I have this error PARSE ERROR ON INPUT "->"

Question

I am tryng to use this example (http://www.haskell.org/haskellwiki/HXT/Practical/Simple2) and when I try to run it always appear this PARSE ERROR ON INPUT "->"

The code where is the problem is this:

getTeams2 = atTag "LEAGUE" >>>
  proc l -> do
    leagName <- getAttrValue "NAME"       -< l

the line in especific is this:

 proc l -> do

so which problem can be?? How can i fix it?

by the way already remove all the "tabs" in the script

Do you have {-# LANGUAGE Arrows #-} set? When I try it in GHCi I get "The last statement in a do block in an arrow command must be an expression", and if I add return leagName after leagName <- getAttrValue ..., it tells me that the expression getAttrValue was found where an arrow command was expected. — bheklilr
– bheklilr, Commented Feb 3, 2014 at 21:29
I running the from CMD on Windows using this command "runhaskell example.hs" Each time i try to running the error appears. I have ran others examples and works. Only have problem with this sentence "proc x->do" BY the way how can i get sure i have the language arrows set? — Darkjaeger
– Darkjaeger, Commented Feb 3, 2014 at 21:49
The bit at the top of the file you linked to says {-# LANGUAGE Arrows #-}. This arrows pragma is absolutely essential to be able to run the code you show, because the proc <something> -> <something> is called "arrow notation" and it is not part of standard Haskell, but rather an extension you can enable in GHC with the arrows pragma. Make sure you also have {-# LANGUAGE Arrows #-}. — kqr
– kqr, Commented Feb 3, 2014 at 21:53

not my job · Accepted Answer · 2014-02-04 14:04:42Z

4

proc l -> do

is special notation for Arrows, and you have to enable it with

{-# LANGUAGE Arrows #-}

at the top of your file.

answered Feb 4, 2014 at 14:04

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