hoelz:

I've been pouring over the Xlib bindings for Haskell, and I've come across the following code:

peekXButtonEvent p = do root <- #{peek XButtonEvent,root} p subwindow <- #{peek XButtonEvent,subwindow} p time <- #{peek XButtonEvent,time} p x <- #{peek XButtonEvent,x} p y <- #{peek XButtonEvent,y} p x_root <- #{peek XButtonEvent,x_root} p y_root <- #{peek XButtonEvent,y_root} p state <- #{peek XButtonEvent,state} p button <- #{peek XButtonEvent,button} p same_screen <- #{peek XButtonEvent,same_screen} p return (root, subwindow, time, x, y, x_root, y_root, state, button, same_screen)

I can't seem to find a definition or an explanation for #{}. Is this some kind of operator for dealing with monads or something?

Nope! But nice guess - if in doubt, its probably to do with monads :-) Its actually hsc2hs preprocessor code, http://www.haskell.org/ghc/docs/latest/html/users_guide/hsc2hs.html#id318486... #peek struct_type, field A function that peeks a field of a C struct will be output. It will have the type Storable b => Ptr a -> IO b. The intention is that #peek and #poke can be used for implementing the operations of class Storable for a given C struct (see the Foreign.Storable module in the library documentation). -- Done