Re: Compare these two (sub)type declarations

["Lance" <lanceboyle@qwest.net>]

Ludovic Brenta wrote:
> Lance writes :
> > What is the difference between these two declarations?
> >
> > subtype Foo is Integer;
>
> Foo is a subtype. It is compatible with Integer and with all other
> subtypes of Integer such as Natural and Positive, i.e. you can convert
> implicitly between all these subtypes. The compiler inserts range
> checks where appropriate.
>
> > and
> >
> > type Bar is new Integer;
> >
> > In fact, what _is_ the second declaration? Would variables of type Bar
> > not be allowed in expressions where Integers are expected?
>
> Bar is a derived type. It is not compatible with Integer, or with any
> subtype of Integer, so the compiler would reject a program that passes
> a Bar to a subprogram that expects an Integer. You can, however,
> convert _explicitly_ between Bar and Integer, just like between any two
> numeric types; the compiler inserts range checks as appropriate.
>
> HTH
>
> > Jerry
>
> Is it Lance, or Jerry now?
>

My name is Jerry B a u c k. I use the lanceboyle address for mailing
lists for spam control reasons (lance boil is a joke in English) and to
keep from polluting my "real namespace" on the internet. I always sign
as Jerry but surprisingly (to me), people usually reply to "Lance." I
live in Tempe, Arizona, USA where I am self-employed.

Thanks for your informative reply.
> -- 
> Ludovic Brenta.