Hi, It sounds like your "use of `ioctl'' at topIO.hs:21:35-60" is passing an "Int" as the 3rd argument to "ioctl", when your instance declaration states that this argument should be a "C'winsize". -Iavor On Wed, Nov 24, 2010 at 11:27 PM, Magicloud Magiclouds wrote:

Hi,  In System.Posix.IOCtl, there is such a class: class Storable d => IOControl req d | req -> d where ioctlReqSource :: req -> CInt  How to instance it? I do it as: data TIOCGWINSZ = TIOCGWINSZ

#starttype struct winsize #field ws_row , CUShort #field ws_col , CUShort #field ws_xpixel , CUShort #field ws_ypixel , CUShort #stoptype

instance IOControl TIOCGWINSZ C'winsize where  ioctlReq _ = #const TIOCGWINSZ

 Then I got: topIO.hs:19:0:    Couldn't match expected type `C'winsize'           against inferred type `Int'    When using functional dependencies to combine      IOControl        (Foreign.C.Types.CUShort         -> Foreign.C.Types.CUShort         -> Foreign.C.Types.CUShort         -> Foreign.C.Types.CUShort         -> C'winsize)        Int,        arising from a use of `ioctl'' at topIO.hs:21:35-60      IOControl        (Foreign.C.Types.CUShort         -> Foreign.C.Types.CUShort         -> Foreign.C.Types.CUShort         -> Foreign.C.Types.CUShort         -> C'winsize)        C'winsize,        arising from a use of `ioctl'' at topIO.hs:20:12-37    When generalising the type(s) for `main' -- 竹密岂妨流水过 山高哪阻野云飞 _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe