[Haskell-beginners] System.USB.writeInterrupt -- confused by error message from type system

Brent Yorgey byorgey at seas.upenn.edu
Wed Feb 27 22:24:29 CET 2013

On Wed, Feb 27, 2013 at 09:06:30PM +0000, emacstheviking wrote:
> HURRAH! I have finally got it to compile...
> I manually deleted the broken packages (I play too much anyway so a tidy up
> was in order) and it still failed with:
> [1 of 1] Compiling Main             ( usb1.hs, usb1.o )
> usb1.hs:64:28:
>     Couldn't match expected type
> `bytestring-'
>                 with actual type `ByteString'

Glad you got it to work!  For future reference, the fact that the
error message includes a package name and version number
(bytestring- instead of
just Data.ByteString.Internal.ByteString) is usually a very strong
indication that the real problem is multiple versions of the package
interfering with one another.


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