I faced the same issue and ended up using an array. Can you help me understand the rest parameter of a function?
I would have to substitute (r, g, b) by (...values) at the function parameters?

// my comment here

Using fold would be better

You could have used the rest parameter in your function, declare a [r,g,b] array was unnecessary

I used 1001 as "first last", but i used the same logic

Almost my answer, but...
return !parens.lenght