module Field4 where --Rename field name 'value1' to 'value2' should success. data Vtree a = Vleaf {value2::a} | Vnode {value2::a, left,right ::Vtree a} fringe :: Vtree a -> [a] fringe t@(Vleaf _ ) = [value2 t] fringe t@(Vnode _ _ _) =fringe (left t) ++ fringe (right t)