Re: Lisp's QUOTE and Mathematica's "Hold"

Nathan Baum wrote:
> Jon Harrop wrote:
>> Nathan Baum wrote:
>>>You misunderstand me. I mean that the Mathematica equivalent of 'X,
>>>which I suppose is just (X), would behave that way.
>>
>> I don't understand. The Mathematica equivalent of 'X is Hold[X]?
>
> No. Because Mathematica has a wildly different evaluation model, its
> equivalent of 'X is simply (X) -- Mathematica keeps evaluating until an
> expression doesn't change. 'X changes when it is evaluated, and
> therefore, from Mathematica's point of view, 'X is equivalent to (X).

I think this is an important point: all Mathematica values are equivalent to
Lisp s-exprs. So all Mathematica equivalents must be quoted at least once.
So (X) cannot be a Lisp equivalent of anything in Mathematica, AFAIK.

>> Note that this has nothing to do with the similarity between QUOTE and
>> Hold. This is entirely to do with evaluation semantics, which are
>> definitely not the same.
>
> How do you propose to judge the similarity of QUOTE and Hold _without_
> considering how they effect the evaluation of expressions?

I'm just comparing the effect of eval on QUOTE and Release on Hold. I'm not
trying to say that the subsequent evaluation of the enclosing expression
works in the same way.

--
Dr Jon D Harrop, Flying Frog Consultancy
http://www.ffconsultancy.com
.

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