Re: Types, subtypes and ranges

[Lao Xiao Hai <laoxhai@ix.netcom.com>]

"Marc A. Criley" wrote:

>
> Hmmm, I've never really considered subtypes a "weakening" of the type
> slightly, though obviously they could be ill-used to that end.  My use
> of them has been in fact to tighten up the typing.

Often, some programmer will declare a lot of subtypes to avoid
some of the strict compile-time type checking on operations.  Also,
without the need for explicit type conversions, one can blithely
assign one type to another without considering the implications,
such as potential range constraints at run-time.

Granted, one must confront the same issue with derived types that
have varying ranges, but we could hope the need for explicit type
conversion makes the programmer stop and consider the possible
consequences of that action.

That being said, the examples you have presented are excellent for
demonstrating the intelligent use of subtypes.

Richard Riehle