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Re: second simple problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg99698] Re: second simple problem
  • From: Peter Pein <petsie at dordos.net>
  • Date: Mon, 11 May 2009 06:26:29 -0400 (EDT)
  • References: <gu666q$9tf$1@smc.vnet.net>

Francisco Gutierrez schrieb:
> Dear sirs:
> I have the following list:
> ex={1,5,7,4,"M",6,7,8,9,1,"M",3}
> I want to replace the M's in the following way: the first M by 5, and the second by2.
> Thus I have a replacement list
> rL={5,2}
> The problem is to get ={1,5,7,4,5,6,7,8,9,1,2,3}
> How can I do this in the most general form (for any length of ex and any number of values of "M")?
> Thanks
> Francisco      
> 
Hi Francisco,
sorry for not answering.
Can anyone please explain, why the "obvious"
Fold[Replace[#1, "M" -> #2] &, ex, {a, b}]
leads to an unchanged "ex"? It is nearly 3 am and I guess it is better to go 
to sleep, than to try to solve this one.
Good night to all,
Looking forward a solution,
Peter.


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