disjoint ranges ?

[Philippe Torres <ptorres@laas.fr>]

A very dumb question but i can't find the right syntax so here i am. 
How can i declare a type or subtype with a disjoint range ?

Example :

If i declare :
---
type Hours is new Integer range 0 .. 23 ;
--
i would like a
---
subtype Lunch_Hours is Hours range 7..9 & 12..14 & 19..21 ;
---
I know this syntax is totally incorrect but i would like to avoid
enumerations since :

1- enumeration types don't accept elements named as numeric literals. I
can't define : type Lunch_hours is (7,8,9,12,13,...);

2- if my range are big, i am in trouble.

Does someone have an idea ?

Thanks in advance
Philippe