Simon, Why did you guys implement TChan on top of your own TVarList instead of a regular list? -- | 'TChan' is an abstract type representing an unbounded FIFO channel. data TChan a = TChan (TVar (TVarList a)) (TVar (TVarList a)) type TVarList a = TVar (TList a) data TList a = TNil | TCons a (TVarList a) Thanks, Joel -- http://wagerlabs.com/