[Haskell-cafe] X Haskell Bindings

[David Roundy]

On 8/16/08, Antoine Latter <aslatter at gmail.com> wrote:
>  The following is a summary of my plan so far.  I'm interested in
>  hearing any suggestions or concerns about what a Haskell library for
>  writing X clients should look like.  This is not a release
>  announcement, and I can't make any promises about when this will be
>  delivered.
>
>  Code is available in darcs:
>  --  darcs get http://community.haskell.org/~aslatter/code/xhb
>
>  Some of the  advantages XCB claims over xlib are:
>   + smaller API
>   + latency hiding when communicating with the X server
>   + direct access to the X protocol
>   + improved threading support
>   + easier to extend
>
>  What I plan for the X Haskell Bindings (XHB) are as follows:

It seems to me that you could make this a bit more haskelly...

>   + All requests to the server are non-blocking (under most circumstances)
>
>   + Requests which produce a reply from the server return a "token" or "receipt"

Why not abstract this token or receipt into a function?

i.e. why not change...

>  > -- | List all of the extensions supported by the server
>  > listExtensions :: Connection -> IO (Receipt (ListExtensionsReply))
>
>  > -- | Query a receipt for a response
>  > getReply :: Receipt a -> IO (Either XError a)

to

listExtensions :: Connection -> IO (IO ListExtensionsReply)

and then you don't need to use a getReply, or a Receipt data type.
This should be equally general, if (as I imagine) the only thing you
can do with a Receipt is to getReply it.  And to me it seems like a
friendly way of describing what this function does.

>  Each X extension defines its own set of errors and events
>  (potentially).  Should all of these be lumped together into one giant
>  sum-type for errors and one for events?

Or maybe just a couple of existential types together with dynamic?
(i.e. like xmonad's SomeMessage)

David