further improvements to "poly_{preds,tags}_{bang,query}" -- better solution to the combinator problem + make sure type assumptions can be discharged
structure ROOT =
struct
structure Codegen =
struct
fun lookup ((k, v) :: xs) l =
(if ((k : string) = l) then SOME v else lookup xs l)
| lookup [] l = NONE;
end; (*struct Codegen*)
end; (*struct ROOT*)