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,
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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