Is Parsec's ParserError missing an Eq instance

8 Sep 2008

      Hi

I am trying to use HUnit to test my Parsec-based parsers.  I have the  
following code:

import Text.ParserCombinators.Parsec

import Test.HUnit

test1 = TestCase $ assertEqual
         "msg"
         (Right '1')
         (parse digit "error" "1")

Running it gives the following error:

HUnitParsec.hs:5:19:
     No instance for (Eq ParseError)
       arising from a use of `assertEqual' at HUnitParsec.hs:(5,19)- 
(8,32)
     Possible fix: add an instance declaration for (Eq ParseError)
     In the second argument of `($)', namely
         `assertEqual "msg" (Right '1') (parse digit "error" "1")'
     In the expression:
           TestCase $ assertEqual "msg" (Right '1') (parse digit  
"error" "1")
     In the definition of `test1':
         test1 = TestCase
               $ assertEqual "msg" (Right '1') (parse digit "error" "1")

Is the missing Eq instance intentional? What is the recommended way to  
use HUnit to test Parsec parsers?

Bests,
Manuel

Is Parsec's ParserError missing an Eq instance

Manuel Holtgrewe