Re: On Formal IS-A definition

On May 9, 4:05 pm, Nilone <rea..._at_gmail.com> wrote:
> On May 9, 3:44 am, David BL <davi..._at_iinet.net.au> wrote:
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> > On May 9, 2:34 am, Nilone <rea..._at_gmail.com> wrote:
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> > > On May 8, 7:11 am, David BL <davi..._at_iinet.net.au> wrote:
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> > > > 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.
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> > > 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.
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> > 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.
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> I see, thanks for the corrections.
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> > 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.

Yes as long as it's not thought that the identifiers are the variables. Received on Sun May 09 2010 - 14:54:25 CEST