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MathGroup Archive 2000

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Re: List operations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg25463] Re: [mg25399] List operations
  • From: Tomas Garza <tgarza01 at prodigy.net.mx>
  • Date: Sun, 1 Oct 2000 02:44:47 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In[1]:=
listA =
{{2, 8}, {1, 3}, {4, 1}, {3, 5}, {4, 6}, {1, 4}, {1, 5}, {1, 5}, {9, 3}, 
{6, 7}};

In[2]:=
Select[listA, 3*#[[1]] + #[[2]]^2 == 12 &]
Out[2]=
{{1, 3}}

Tomas Garza
Mexico City


"Matt Herman" <Henayni at hotmail.com> wrote:

> Suppose I have a list of ordered pairs {{a1,b1},{a2,b2},...,{an,bn}}.
> What is an efficient way of pulling out all the pairs such that, if I 
do
> an operation on the first element in the list, and another on the
> second, and I sum them, they equal some predetermined constant?
>
> For instance, say 3*listpart[[1]]+listpart[[2]]^2


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