adamc@834: fun exec [m ::: Type -> Type] (_ : monad m) [ts ::: {Type}] r (fd : folder ts) =
adamc@834:     foldR [m] [fn ts => m $ts]
adamc@834:     (fn [nm :: Name] [v :: Type] [rest :: {Type}] [[nm] ~ rest] action acc =>
adamc@834:         this <- action;
adamc@834:         others <- acc;
adamc@834:         return ({nm = this} ++ others))
adamc@834:     (return {}) [ts] fd r