Re: Towards a definition of atomic

From: Jan Hidders <hidders_at_gmail.com>
Date: Sun, 3 Feb 2008 05:33:32 -0800 (PST)
Message-ID: <3cdcbc6b-cdc6-47dc-8af7-4d0e1ed10839_at_j78g2000hsd.googlegroups.com>


On 1 feb, 19:55, Marshall <marshall.spi..._at_gmail.com> wrote:
>
>
> The concept we are running into here is the same as "alpha
> equivalence"
> from lambda calculus.
>
> Consider these two programs:
>
> Program 1:
>   let x=5;
>   let y=3;
>   x+y;
>
> Program 2:
>   let a=5;
>   let b=3;
>   a+b;
>
> Are these programs identical? It depends on what we mean by
> "identical." Certainly they calculate the same value, but certainly
> that's not enough to consider them identical.
>
> If we consider the two programs as strings of symbols, then
> obviously they are different. However clearly they are very closely
> related, and we can formalize this perception, and this formalization
> is called alpha equivalence. Roughly, the two programs are alpha
> equivalent because they have identical structure if we ignore the
> specific choices of variable names. From this perspective, there is
> no significance to the specific choice of "x" or "a" or whatever as
> variable names, but that doesn't mean the names are meaningless,
> because the distinct names encode identity within the structure
> they are embedded in.

This is the usual explanation for why and how abstract identifiers can have meaning. So does that mean you think that abstract identifiers can sometimes actually have meaning and be useful?

  • Jan Hidders
Received on Sun Feb 03 2008 - 14:33:32 CET

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