Re: Principle of Orthogonal Design

On Feb 8, 3:37 pm, David BL <davi..._at_iinet.net.au> wrote:
> On Feb 9, 2:12 am, Marshall <marshall.spi..._at_gmail.com> wrote:
> > On Feb 7, 3:19 pm, David BL <davi..._at_iinet.net.au> wrote:
> > > On Feb 8, 4:43 am, Marshall <marshall.spi..._at_gmail.com> wrote:
> > > >
> > > > Well, at the very least we have to be careful to distinguish
> > > > the use of the equals sign between its use as the equality
> > > > relation and its use as name-binding.
>
> > > In a way I don't really see a fundamental distinction. I think the
> > > special syntax is needed to deal with variable names that are local to
> > > a sub-expression, because with implicit variable names on predicates
> > > we can get name clashes. These would be impossible to deal with if
> > > all variables had global scope.
>
> > If we substitute "lexical scope" for "sub-expression" in the above
> > then I agree. I recoil from the idea of names that are local
> > just to a specific sub-expression.
>
> Please forgive my ignorance, but what is the distinction? Are you
> saying that a lexical scope should be more general - ie a lexical
> scope may not correspond to a particular sub-expression?

The term "sub-expression" can refer to syntactic units that are quite tiny: "3+4*5=23" has "4*5" as a sub-expression, but that's too small to have its own namespace. However quantifiers in logic come with their own lexical scope. (They must, since they introduce local names.)

This may just be me being picky, and/or my programming language bias showing through.

Marshall Received on Sat Feb 09 2008 - 01:26:45 CET