How passing vectors to modules and use them within the module?

Hi, I am new to Openscad and very enthusiastic about it. For resolving my problem below I already searched the internet, the site of Openscad and the community of openscad, with no result. So:

If I define a module as following,

module move(size = [0, 0, 0], protrusion_x = 0, protrusion_y = 0, protrusion_z = 0)

how am I capable to evaluate the vector size? I tried the following without success:


    size.x = size.x + protrusion_x;

And

    size[0] = size[0] + protrusion_x;

What is the right way to achieve this?

The module should do the following:

module move(size, protrusion_x = 0, protrusion_y = 0, protrusion_z = 0)
{
    size.x = size.x + protrusion_x;
    size.y = size.y + protrusion_y;
    size.z = size.z + protrusion_z;
    move(size);
}

move(size, x = 0.1) cube(cube_size);

Any help is appreciated

Best wishes

Christian
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> size[0] = size[0] + protrusion_x;

You can't reassign identifiers like that, see
https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/The_OpenSCAD_Language#Variables

size[0] size[1] etc are how to reference the value.
size.x .y .z is a shortcut that can be used for the first three elements,
but not to assign them

Try

module move(size=[0, 0, 0], protrusion_x = 0, protrusion_y = 0, protrusion_z
= 0)
{
    vector = [ size.x + protrusion_x, size.y + protrusion_y, size.z +
protrusion_z];
    translate(vector)
      DoSomeThing();
}




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size[0] = size[0] + protrusion_x; 

[...]
    vector = [ size.x + protrusion_x, size.y + protrusion_y, size.z +
protrusion_z];

Or if you want an intermediate variable, that's OK too:

tmp_x = size.x + protrusion_x;
tmp_y = size.y + protrusion_y;
tmp_z = size.z + protrusion_z;

or with tmp as an array:

tmp = [
    size.x + protrusion_x,
    size.y + protrusion_y,
    size.z + protrusion_z
];

or you might consider having protrusion_* be an array itself, which would make it even simpler:

tmp = size + protrusion;

You just can't change the value of an existing variable (or array element).

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There are many things to clarify in the code you show:

1. You can evaluate an expression into a new! local variable (note: a
variable in OpenSCAD is always a constant in the relevant scope):

module move(size = [0, 0, 0], protrusion_x = 0, protrusion_y = 0,
protrusion_z = 0)
  new_size = size + [protrusion_x, protrusion_y, protrusion_z];

But you can't set single components of a variable meant to contain a vector
(=list) or matrix value (=list of lists). However OpenSCAD lets you write:

module move(size = [0, 0, 0], protrusion_x = 0, protrusion_y = 0,
protrusion_z = 0)
  size = size + [protrusion_x, protrusion_y, protrusion_z];

This is because the local "variable" *size* shadows the parameter *size*
after it is defined. Note that the parameter *size* can be used in the
R-value of that definition, where it is not yet shadowed. Similarily, the
parameter *size* would shadow a global variable named *size*. Thus you get
three different entities (two being shadowed) by writing:

size= [0,0,0];
module move(size = size, protrusion_x = 0, protrusion_y = 0, protrusion_z =
0)
  size = size + [protrusion_x, protrusion_y, protrusion_z];

2. You define a recursion by
module move(size = [0, 0, 0], protrusion_x = 0, protrusion_y = 0,
protrusion_z = 0)
  move(size + [protrusion_x, protrusion_y, protrusion_z]);

Don't do this without using a logic to that stops the recursion.

3. You seem to intend to define move() as an operator (like translate()
rotate() and so on) that modifies the construction parameters. To be honest,
I would postpone this enterprise until you feel OK with the basics. A
solution for this would involve a special purpose variable characterized by
$ that is handed to and used by operands of such an expression. E.g.

move([10, 10, 10], 1, 2, 13) cube($size);  

module move(size = [0, 0, 0], protrusion_x = 0, protrusion_y = 0,
protrusion_z = 0)
{
  $size = size + [protrusion_x, protrusion_y, protrusion_z];
  children();
}





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