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Re: ReplaceAll and rules from a list v7.0

  • To: mathgroup at smc.vnet.net
  • Subject: [mg104244] Re: ReplaceAll and rules from a list v7.0
  • From: "Nasser M. Abbasi" <nma at 12000.org>
  • Date: Sun, 25 Oct 2009 01:04:54 -0400 (EDT)
  • References: <hbu7qi$7hn$1@smc.vnet.net>

"kristoph" <kristophs.post at web.de> wrote in message 
news:hbu7qi$7hn$1 at smc.vnet.net...
> Hi,
>
> Suppose I have the equation
>
> x=a+b
>
> and the list
>
> l={{1,1},{2,2},{3,3}}
>
> How can I quickly assign the list to the above equation, that is, I
> would like to get the following result
>
> {2,4,6}
>
> The first element of each sub-list should be assigned to a and the
> second to b.
>
> Thanks in advance.
> Kristoph
>

This is one of the problems there there is probably 10 ways to do in 
Mathematica.

Here is one way, but I am sure there is a short way to do this. Map a 
replacement rule to the list.

x = a + b;
list = {{1, 1}, {2, 2}, {3, 3}};

(x /. {a -> #1[[1]], b -> #1[[2]]} & ) /@ list


{2, 4, 6}

--Nasser 



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