Switch on argument type - module

Question

Using Open SCAD, I have a module that, like cube(), has a size parameter that can be a single value or a vector of three values. Ultimately, I want a vector of three values.
If the caller passes a single value, I'd like all three values of the vector to be the same. I don't see anything in the language documentation about detecting the type of an argument. So I came up with this hack:
module my_cubelike_thing(size=1) {
dimensions = concat(size, size, size);
width = dimensions[0];
length = dimensions[1];
height = dimensions[2];
// ... use width, length, and height ...
}
When size is a single value, the result of the concat is exactly what I want: three copies of the value.
When size is a three-value vector, the result of the concat is nine-value vector, and my code just ignores the last six values.
It works but only because what I want in the single value case is to replicate the value. Is there a general way to switch on the argument type and do different things depending on that type?

Answer 1

If type of size only can be single value or a vector with 3 values, the type can helpwise be found by the special value undef:
a = [3,5,8];
// a = 5;
if (a[0] == undef) {
dimensions = concat(a, a, a);
// do something
cube(size=dimensions,center=false);
}
else {
dimensions = a;
// do something
cube(size=dimensions,center=false);
}
But assignments are only valid in the scope in which they are defined , documnetation of openscad.
So in each subtree much code is needed and i would prefere to validate the type of size in an external script (e.g. python3) and write the openscad-code with the assignment of variables to a file, which can be included in the openscad-file, here my short test-code:
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import os
# size = 20
size = [20,15,10]
if type(size) == int:
dimensions = [size, size, size]
elif type(size) == list:
dimensions = size
else:
# if other types possible
pass
with open('variablen.scad', 'w') as wObj:
for i, v in enumerate(['l', 'w', 'h']):
wObj.write('{} = {};\n'.format(v, dimensions[i]))
os.system('openscad ./typeDef.scad')
content of variablen.scad:
l = 20;
w = 15;
h = 10;
and typeDef.scad can look like this
include <./variablen.scad>;
module my_cubelike_thing() {
linear_extrude(height=h, center=false) square(l, w);
}
my_cubelike_thing();