Re: Bug in Mathematica 8 vs Mathematica 7: SeriesData

• To: mathgroup at smc.vnet.net
• Subject: [mg116833] Re: Bug in Mathematica 8 vs Mathematica 7: SeriesData
• From: Daniel Lichtblau <danl at wolfram.com>
• Date: Wed, 2 Mar 2011 04:32:19 -0500 (EST)

```GidiL wrote:
> Dear All!
>
> A long time ago I asked about the right way of using SeriesData for
> multiple expansions.
>
> For example, if you want a multiple expansion of a metric in general
> relativity, it is quite simple to input:
> SeriesData[r, Infinity, {-1, -2, -3}, 0, 3, 1]
> In Mathematica 7 this line is accepted as is, without any error
> messages or problems.
>
> Yet, try this in Mathematica 8. You will get the following error
> message:
> SeriesData::sdatv: "First argument 1/r is not a valid variable."
>
> Does anyone know what has changed in version 8? Why should such a
> simple expression be invalid in version 8 but be OK in version 7? I
> find it quite strange.
>
> Would appreciate any help!
>
> Cheerio,
>
> Gideon
>

It works fine for me.

In[411]:= SeriesData[r, Infinity, {-1, -2, -3}, 0, 3, 1]

Out[411]= SeriesData[r,
DirectedInfinity[1], {-1, -2, -3}, 0, 3, 1]

But direct input of a XXXData object is generally a bad idea. Especially
as these can change form over releases. Why not just use the Series that
spawns it?

In[420]:= Series[-1/(1 - 1/r)^2, {r, Infinity, 2}]

Out[420]= SeriesData[r,
DirectedInfinity[1], {-1, -2, -3}, 0, 3, 1]

Daniel Lichtblau
Wolfram Research

```

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