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I have two Functions, f[] and g[]. f is passed some values ,say {w,x,y,z} and I want to send one of those to g say x. I don't want this operation to interfere with other operations.

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    $\begingroup$ can you be more specific? eg why does g[x_]:=x; f[{w_,x_,y_,z_}]:=g[x] not work? $\endgroup$ – acl Dec 19 '12 at 12:31
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    $\begingroup$ f[l_]:=(g[First@l]; whatever) $\endgroup$ – ssch Dec 19 '12 at 12:33
  • $\begingroup$ @acl fine i'l tell you the entire problem. $\endgroup$ – santhosh Dec 19 '12 at 12:37
  • $\begingroup$ you don't need to put the entire problem here, just some sort of minimal example $\endgroup$ – acl Dec 19 '12 at 12:38
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    $\begingroup$ The better you explain your problem to us, the better the chances to get good answers. Your question style so far is kind of short bordering on incomplete. $\endgroup$ – Yves Klett Dec 19 '12 at 12:41
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Is this what you have in mind by any chance? I'm simply using an external variable to store the x passed to f when f is called. The Module is there so that that external variable is only known by f and g and you don't accidentally use it in other places

Module[{var},
 f[{w_, x_, y_, z_}] := (var = x; 8);
 g[] := var
 ]

So now if you run

f[{1, 2, 3, 4}]

you get

(* 8 *)

But next time you run g[] you get the "x argument" passed to f the last time it was called

g[]

(* 2 *)
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