typeof := λ(: term S). (: (
   (let found TAny)
   (let tctx s-type-list)
   (while (non-zero tctx) (match tctx (
      ()
      ( (STSeq( rst s tt )) (
         (if (is( s term )) (
            (set found tt)
            (set tctx STEOF)
         ) (
            (set tctx rst)
         ))
      ))
   )))
   found
) Type);