[artisin]

Efficient != effective, and the author outlines as much. Regardless, while you're technically correct, it's kinda like saying the Fantasy Land Specification[1] (aka the "Algebraic JavaScript Specification") is pure. The problem is that purely functional fantasy lands rarely exist outside of fairytales. In other words, life is a lot like JavaScript and never that simple.

[1] - https://github.com/fantasyland/fantasy-land

[avereveard]

never said purely functional, but there are only 4 data channels in each method (input, return, calling another method, setting a state) - and if you constrain your class design to pick only 2 for each method, your life is just a tad easier.

and doesn't matter how bad the rest of the world is, rest of the world is some other maintainer's problem, you just encapsulate it.