Setting local variables with another function

Question

I'm working on a package with a lot of functions using Module, which all begin by unpacking the arguments into local variables. I'd like to store this unpacking code in a separate function called Setup and just call it in each function, but the local variables don't make it out.

A simple example:

Setup := (z = x^2);

g[x_] := Module[{z},
Setup;
Return[z]
];

g[3]

returns z$2599 when I'd like it to return 9. My real Setup is much longer of course, which is why I'd rather recycle it than rewrite it in each function.

Is there an easy way to make this work?

Update: A less minimal example

Here's a slightly less minimal example that captures more of the real situation. In my real problem, the Setup code is about a page long. At this point, I'm too far into this to change how I store the z[i] to a list!

Setup := (
numX = Length[x];
Do[z[i] = StringLength[x[[i]]], {i, numX}]
)

g[x_List] := Module[{numX, z},
Setup;
Table[z[i], {i, numX}]
]

g[{"hi", "there"}] should return {2,5}.

Answer 1

The thing to do is pass the parameters to setUp and make that function hold its arguments.

SetAttributes[setUp, HoldAll]
setup[z_, numX_, x_] := (numX = Length[x];
  Do[z[i] = StringLength[x[[i]]], {i, numX}])

g[x_List] := Module[{numX, z},
  setup[z, numX, x];
  Table[z[i], {i, numX}]]

g[{"hi", "there"}]

(* Out[1016]= {2, 5} *)

Answer 2

Why don't you use a function for it?

setup[x_, y_] := {x^2 - y, y*x^3}
f[args___] := 
    Module[{u,v},
        {u,v} = setup[args];
        u + v
    ]

I showed this to prove that the code can be concise but I would write out the arguments of f explicitly as f[x_, y_] instead of f[args___] to restrict the forms that match.