[jasone]

Type correctness is pure power, or a waste of time, depending on... perspective! I can't help thinking back to the highly illustrative example of my first enhancement to Facebook's production website as a "bootcamper" in 2009.

I was tasked with adding proper honorifics for Japanese speakers (it's complicated in the general case, but I was just getting as far as "San"). I wrote some straightforward PHP code to implement this feature, but of course it broke in production for some nontrivial percentage of requests. Why? Because the string I was adding the honorific to wasn't always a string. WTF? What is the proper course of action when strings aren't strings? Well, in this case the answer was a run-time type-check guard on the code I had added.

Keith Adams, my esteemed colleague, likened this to "dogs and cats living together", perhaps revealing a fondness for simpler days when Ghostbusters trod the streets. Keith may not have gone as far as lauding OCaml's type system in those dark early days, but I will do so now (and perhaps he would too).