Re: On Formal IS-A definition

On May 9, 3:44 am, David BL <davi..._at_iinet.net.au> wrote:
> On May 9, 2:34 am, Nilone <rea..._at_gmail.com> wrote:
>
> > On May 8, 7:11 am, David BL <davi..._at_iinet.net.au> wrote:
>
> > > Values are immutable.  Variables accessed by imperative programs are
> > > usually mutable.  Sets are values.  If a set contained a variable then
> > > it wouldn't be immutable.
>
> > We can generalize values and variables to elements of domains, where a
> > value is any element of a domain while a variable is an element of a
> > domain for which a homomorphism to another domain is defined.
> > Assigning to a variable would reduce to modification of the
> > homomorphism, so sets containing variables would not be modified by
> > assignment to a variable.
>
> Wrong.  You can't modify a homomorphism just like you can't modify a
> number or a set.  Homomorphisms are values and are therefore
> immutable.

I see, thanks for the corrections.

> You have invented a homomorphism variable to hold a
> homomorphism value.  What you claimed were variables were just values
> intended to act as inputs to a homomorphism function.

Yes, I'm saying variables have identity which are values we can form sets over. Received on Sun May 09 2010 - 10:05:20 CEST