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MathGroup Archive 2006

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Re: ReplaceAll applied to List

  • To: mathgroup at smc.vnet.net
  • Subject: [mg72331] Re: ReplaceAll applied to List
  • From: dh <dh at metrohm.ch>
  • Date: Tue, 26 Dec 2006 06:22:44 -0500 (EST)
  • References: <em8jdu$pel$1@smc.vnet.net>


Hi Hannes,

parts of an expression also includes Heads. And a Head can be atomic or 

not-a-list.

Daniel



Hannes Kessler wrote:

> Hello,

> 

> I want to apply transformation rules to those elements of a list which

> are not lists themselves. The structure of the list is unknown in

> advance.

> 

> The following simple examples illustrate my my problems with ReplaceAll

> and List:

> 

> Expected result:

> {1., {2}, 3} /. x_?NumericQ :> g

> --> {g,{g},g}

> 

> Unexpected result - inspite of AtomQ[{1., {2}, 3}] giving False

> {1., {2}, 3} /. x_?AtomQ :> g

> --> g[g, g[g], g]

> 

> Similarly unexpected result - inspite of Not[ListQ[{1., {2}, 3}]]

> giving False

> {1., {2}, 3} /. x_?(Not[ListQ[#]] &) :> g

> --> g[g, g[g], g]

> 

> Any explanations for this behavior?

> 

> Thanks in advance,

> Hannes Kessler

> 



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