prioritize_num : unit -> unit
# prioritize_real();; val it : unit = () # type_of `x + y`;; val it : hol_type = `:real`
# type_of `x + 1`;; val it : hol_type = `:num`
# prioritize_num();; val it : unit = () # type_of `x + y`;; val it : hol_type = `:num`
# type_of `(x:real) + y`;; val it : hol_type = `:real`