Re: "access constant" discriminant

[Kilgallen@SpamCop.net (Larry Kilgallen)]

In article <3E4E9248.3E71D984@adaworks.com>, Richard Riehle <richard@adaworks.com> writes:

> A function may have a an access parameter, which almost has in
> semantics.   However,  it is possible to modify a component of
> an access parameter.  I would like the option of preventing that
> with,
> 
>                function F (X : access constant parameter-name) return
> some-type;
> 
> This would make it illegal for the function to modify the components of
> an access parameter.   Without the word constant, one could still modify
> such components, but including it would make absolutely clear, in the
> contract, that such side-effects would be impossible.

Why is it necessary to have the parameter be an access type ?