       Re: Re: Union - simple question

• To: mathgroup at smc.vnet.net
• Subject: [mg49097] Re: [mg49086] Re: Union - simple question
• From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
• Date: Thu, 1 Jul 2004 05:25:44 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```On 30 Jun 2004, at 18:34, Maxim wrote:

> Another point is that SameTest->Automatic is something rather obscure,
> it is not the same as SameTest->SameQ or SameTest->Equal:
>
> In:=
> Union[{1`20, 1`30}]
> Union[{1`20, 1`30}, SameTest -> SameQ]
>
> Out=
> {1.0000000000000000000, 1.00000000000000000000000000000}
>
> Out=
> {1.0000000000000000000}
>
> Definitely there are grounds for confusion.
>
> Maxim Rytin
> m.r at inbox.ru
>
As far as I know, the option value Automatic is never exactly equal to
any other built-in option value, and why should it be? For example, the
default value Automatic for the option ComplexityFunction in Simplify
often but not always coincides with LeafCount. Here is an example from
a past MathGroup posting:

Simplify[-4*(16 + 4*L^2*(-1 + 3*u^2))]

-4*(4*(3*u^2 - 1)*L^2 + 16)

Simplify[-4*(16 + 4*L^2*(-1 + 3*u^2)),
ComplexityFunction -> LeafCount]

L^2*(16 - 48*u^2) - 64

Andrzej Kozlowski
Chiba, Japan
http://www.mimuw.edu.pl/~akoz/

```

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