Re: Expressions versus the value they represent

From: David BL <davidbl_at_iinet.net.au>
Date: Thu, 15 Apr 2010 20:41:36 -0700 (PDT)
Message-ID: <9c13285e-8455-4250-876f-d7444d3be299_at_8g2000yqz.googlegroups.com>


On Apr 16, 10:52 am, paul c <toledobythe..._at_oohay.ac> wrote:
> David BL wrote:
>
> ...
>
> > I'm not sure what you mean by saying that a relvar is a pointer. What
> > does it point at? Or do you mean a relvar name is like a pointer that
> > points at an assignable variable within a physical database?
> > ...
>
> Nor I you. As I said, a relvar is a pointer, so not it's confusing to
> say it's 'like' one. I thought it 'pointed' to a value, maybe there is
> some cultural language nuance that I'm not able to comprehend that
> somehow makes a difference in the eyes of some beholder or othe. Maybe
> Bob B can explain the difference between a relational pointer and some
> other kind of pointer but I would have thought the difference was patent
> regardless of context. (I think 'assignment' is a difficult notion but
> am glad you mentioned it.) Personally, for practial reasons if none
> other, I would prefer to think of a pointer as being a pointer,
> regardless of cultural context.

Below 'variable' is restricted to something that can be accessed by imperative statements, and not to be confused with a FOL variable.

I don't say a variable points at a value. I say a variable *holds* a value. I restrict my usage of the word "pointer" to mean a *value* that represents an address or you could say an identifier for a variable. So a pointer points at a variable, not directly at a value.

E.g. In C++

   int x = 10;
   int* p = &x;

x is not a pointer. x is a variable that holds the value 10. p is a pointer variable that holds a pointer value. The pointer value points at the variable named x. There is no concept of a pointer value that points at the value 10. I don't understand what that could mean. Note that C++ outlaws the expression &10. Received on Fri Apr 16 2010 - 05:41:36 CEST

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