con gui (t :: Type) (ctx :: {Unit}) = [[Dyn] ~ ctx] => t -> xml ([Dyn] ++ ctx) [] []

fun gui_xbody [[Dyn] ~ _] x = x
fun gui_xtable [[Dyn] ~ _] x = x

fun mkGui [t ::: Type] [ctx ::: {Unit}] (toXml : [[Dyn] ~ ctx] => t -> xml ([Dyn] ++ ctx) [] []) = @toXml

fun toXml [t ::: Type] [ctx ::: {Unit}] [[Dyn] ~ ctx] (toXml : gui t ctx) = toXml