Types vs Subtypes (was: Re: Copy vector in Ada)

[Simon Wright <simon@pushface.org>]

"Yannick Duchêne (Hibou57)" <yannick_duchene@yahoo.fr> writes:

> All of this also explains why a subtype is not the same as a type
> derivation (and is even the opposite), and Ada is nice to provide this
> distinction (I know no other language with this, even SML don't have
> this). At least, the existence of a notion of subtype, makes things
> like constants, parameter modes and others, describable in the own
> terms of Ada, properly (Dmitry gave a good example).

I suppose it's because I trained as a physicist, not a mathematician,
but I find I can use Ada perfectly well without worrying about all these
arcane distinctions.