[Hat] hat error with HUnit: Variable not in scope: `TPrelude.fnegate'

[Malcolm Wallace]

Shae Matijs Erisson <shae@ScannedInAvian.com> writes:

> I'm using HUnit (http://hunit.sf.net/)
> 
> /home/shae/src/haskell/libraries/THUnitText.hs:64:
>     Variable not in scope: `TPrelude.fnegate'

The problem here is with hat-trans - in the following definition,

    put line pers (-1) = do ...; return (-1)

it has mistakenly interpreted the negative number literal on the left
hand side as a variable binding for negate.  Hence, in the transformed
version of the code, it has used the lambda-bound form `fnegate'
on the right, instead of the real let-bound variable `gnegate'.

Until we can find a fix for hat-trans, here is a workaround for your
application.  Replace the negative numeric literal pattern with another
form, such as a guard.  For instance:

--- HUnitText.lhs	Thu Feb 21 20:21:13 2002
+++ HUnitText.lhs.new	Fri Jul 26 10:43:40 2002
@@ -55,7 +55,8 @@
 > putTextToHandle handle showProgress = PutText put initCnt
 >  where
 >   initCnt = if showProgress then 0 else -1
->   put line pers (-1) = do when pers (hPutStrLn handle line); return (-1)
+>   put line pers  cnt | cnt == (-1)
+>                      = do when pers (hPutStrLn handle line); return (-1)
 >   put line True  cnt = do hPutStrLn handle (erase cnt ++ line); return 0
 >   put line False cnt = do hPutStr handle ('\r' : line); return (length line)
 >     -- The "erasing" strategy with a single '\r' relies on the fact that the

Regards,
    Malcolm