John Carmack on mutable variables

Love Carmack, but hard disagree on this and a lot of similar functional programming dogma. I find this type of thing very helpful:

    classList = ['highlighted', 'primary']
    if discount:
        classList.append('on-sale')
    classList = ' '.join(classList)

And not having to think about e.g. `const` vs `let` frees up needless cognitive load, which is why I think python (rightly) chose to not make it an option.