I don't know about this implementation in particular, but in general a cons cell is just an object with two slots in it. You can use it to represent a list (by putting another cons or nil in the cdr), but you can also use it to represent other things. For example, a pair, by putting an arbitrary object in the car and cdr. This is a pretty common technique, see "a-list" for one application.
Because the useful types of optimisation around undefined behaviour aren't:
"we can prove that your program definitely contains undefined behaviour, so we'll compile it into 'rm -rf /', mwahahaha"
but rather:
"if property P about your program is false, then it would definitely contain undefined behaviour, therefore P must be true"
followed by using P to do useful optimisations.
This applies even when your original program contains zero undefined behaviour. Warning here isn't useful.
Income tax is still very visible in NZ. On your payslip it lists the before-tax value, and then deductions for PAYE, student loan payments, etc. Plus wages/salary are still expressed as a before-tax rate, so you can see the disparity there too.
I get the argument, but whether or not I /want/ to pay taxes, I still have to, so why make it inconvenient? The NZ government finds plenty of other ways to make me angry and upset anyway.
