Modular integers

["Lars" <lars-remove_me-m@gmx.net>]

Hi,

I was able to create an unsigned 64-bit integer using

    type unsigned_64_bit_integer is mod 2**64;

Then I defined a subtype:

    subtype safe_unsigned_64_bit_integer is unsigned_64_bit_integer range 0
.. 2**64-1;

When a variable of type unsigned_64_bit_integer contains 2**64-1 and you add
1, it is "reset" to 0, as expected.
When a variable of type safe_unsigned_64_bit_integer contains 2**64-1 and
you add 1, no exception is raised and it is "reset" to 0.

Why is that? Shouldn't the compiler be able to insert a check that throws an
exception if an overflow occurs?

-Lars