

Ask HN: What's the fnid in the URL? - adityar

What&#x27;s it used for and how is it calculated? 
Ex: https:&#x2F;&#x2F;news.ycombinator.com&#x2F;x?fnid=ErFrwPqYY6tmu1v2had2pg
======
patio11
HN is written in Arc, a Lisp dialect. One programming idiom in Lisp is
"continuations." If you click on that link, you execute the identified
continuation.

This idiom is widely used internally in HN, most commonly for e.g. stateful
things like showing the 4th page of someone's comment history. (That could
arguably be done in a non-stateful way, but it isn't.)

