Happy Question

My hand-written S-expression parser for HScheme is very very slow. Really quite a bit slower than it ought to be. So I'd like to switch to Happy instead. The problem is my parser should be monadic, but the monad type is generalised (basically of the form (context m) => m). Is there a way of switching on monadic-ness, so I can have a monadic happyError, but without giving type signatures to happyThen and happyReturn? Or else allowing a class context for the type signatures? -- Ashley Yakeley, Seattle WA