(bvslt s t) abbreviates
      (or (and (= (extract[|m-1|:|m-1|] s) bit1)
               (= (extract[|m-1|:|m-1|] t) bit0))
          (and (= (extract[|m-1|:|m-1|] s) (extract[|m-1|:|m-1|] t))
               (bvult s t)))