Groups > comp.soft-sys.math.mathematica > #2063

Re: Please Help Eliminate My Ignorance

From	Sseziwa Mukasa <mukasa@gmail.com>
Newsgroups	comp.soft-sys.math.mathematica
Subject	Re: Please Help Eliminate My Ignorance
Date	2011-05-03 09:48 +0000
Organization	Steven M. Christensen and Associates, Inc and MathTensor, Inc.
Message-ID	<ipoj1c$g9d$1@smc.vnet.net> (permalink)

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On May 2, 2011, at 6:52 AM, Michael Mandelberg wrote:

> Why does Mathematica like the first, but not the second?
>
> 1.
> Clear[x, testp, p];
> test[p_] :=  Append[p, p[[4]]];
>
>
> 2.
> Clear[x, testp, p];
> test[p_] := x = 1; Append[p, p[[4]]];
>
> Part::partd: Part specification p[[4]] is longer than depth of object.
>>>
>
> Append::normal: Nonatomic expression expected at position 1 in
> Append[p,p[[4]]]. >>

Your second case is a compound statement and the parts are evaluated independently.  If you want to assign 1 to x in test wrap it in a scoping construct:

test[p_]:=Block[{},x=1;Append[p,p[[4]]]]

Regards,
	Ssezi

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Re: Please Help Eliminate My Ignorance Sseziwa Mukasa <mukasa@gmail.com> - 2011-05-03 09:48 +0000

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