The Problem

I would like to automatically set the scroll offset to half the value of vim.opt.lines (see :help lines).

I Tried

I tried the following:

vim.opt.scrolloff = vim.opt.lines // 2

I Expected

I expected this to retrieve the current value of vim.opt.lines, divide it by 2, and assign the result to vim.opt.scrolloff.

Results

This is what happened instead (upon reopening NeoVim):

Error detected while processing C:Users<user>AppDataLocalnviminit.lua:
E5112: Error while creating lua chunk: C:<user>AppDataLocalnviminit.lua:24: unexpected symbol near '/'
Press ENTER or type command to continue

My Questions

1. Is this a syntax error?
2. Is there any way to access vim.opt.lines or an equivalent value?
3. Can I not access vim option values? Is this universally true, or only true in this situation because vim options are still being defined while init.lua is being processed?

Note

I have previously just used

vim.opt.scrolloff = 26

which worked fine, but I was experimenting and wonering whether I could set it dynamically, which would be useful if I ever want to set the scroll offset to a quarter of the screen or something.