Ah yes, this is a genuine bug.   Haskell 98 changed at some point to allow identifiers and field labels with a leading ‘_’, but the library didn’t keep pace.

I’ll fix GHC. 

HOWEVER, the sad thing is that the same bug is in the Haskell 98 Report itself, now begin printed.  The definition of lex is wrong. 

Ah well, I knew this would happen.  I’d better start keeping a new bug list!

Simon

-----Original Message-----
From: Jong Keun Na [mailto:jongkn@microsoft.com]
Sent: 10 February 2003 02:48
To: Simon Peyton-Jones; haskell-cafe@haskell.org
Subject: RE: Auto generated instance codes through 'deriving'

The following code snippet not works correctly.

>data Obj = Obj {_id, p1, p2::Int} deriving (Show, Read)

>showObj :: Obj -> String

>showObj o = show o

>main = do print (showObj (read "Obj {_id=1,p1=10,p2=20}"))

>              return ()

The reason is because I used the property name with underscore char like “_id”.

Looking into auto generated class codes and seeing they show it should encompass identifiers with special characters with parenthesis, so I tried "Obj {(_id)=1,p1=10,p2=20}" as argument of read func. But, the result is same, parse error.

Is this problem by-design or bug? Or Am I missing any point?

Thanks,

/JongKeun

-----Original Message-----
From: Simon Peyton-Jones
Sent: Friday, February 07, 2003 5:41 PM
To: Jong Keun Na; haskell-cafe@haskell.org
Subject: RE: Auto generated instance codes through 'deriving'

Try -ddump-deriv

            http://haskell.cs.yale.edu/ghc/docs/latest/html/users_guide/options-debugging.html#DUMPING-OUTPUT

Simon

-----Original Message-----
From: Jong Keun Na [mailto:jongkn@microsoft.com]
Sent: 07 February 2003 06:15
To: haskell-cafe@haskell.org
Subject: Auto generated instance codes through 'deriving'

Hello folks,

Is there any method with which I can see instance’s codes generated automatically by using ‘deriving’ keyword in GHC?

I’m curious in how GHC generates ‘Read’ class’s instance code for user-defined data type.

Any help will be great appreciated.

/JongKeun