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Comment by ender7 | Hacker News Reader

This article is just a recapitulation of the old pure functional programming vs. imperative programming argument but wrapped up in new packaging. Most of these issues, such as needing to validate types at codebase boundaries, functions that have side effects, and unsound static type systems, could just as easily be leveled at most imperative languages (C++, Java).

So yeah, go use a proper functional language (many of which compile to JS!). Complaining that an imperative language isn't a soundly-typed functional language is tautologically true I guess, but who cares?

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It's not really, though. Because even pure FP folks read this article and say, "This is just nonsense and ill-considered propaganda."

For example, the idea that you can't trust Typescript because it might call untyped code but you CAN trust Purescript is just wrong. It's not even just wrong, it's utterly misrepresentative of what actually happens in Elm and Purescript. It's misinformation.

Could you elaborate? Why is it wrong/misinformation?

Not OP, but I'd guess the idea is that calling untyped code in TS is basically Pushing the Big Red Button, or Launching the Nukes™. When doing that in TS, you do it knowing it's your own responsibility to test and establish trust in the code. And Elm and PureScript are the same. In other words, Elm and PureScript won't save you from screwing it up the way you can with TS.

All pure/statically typed languages have escape hatches. It has been leveraged as a counter-argument to using them. But but but, they will say, Haskell has unsafePerformIO!!! Well, yeah, sure it does. You can subvert the borrow checker of Rust, too.

But you have to do it explicitly. You can grep your code base for "unsafe" (literally). You can lint for that. You can code review for that. You can document it. And that's what makes it OKish. In a way, types are like big fat oven mitts, and you're the lead programmer of a bakery, where you pop buns in the oven all day. You can discard the oven mitts for a time, though, and do whatever delicate work you need your actual fingers for. Just don't touch the hot stuff, lest you get yourself burned!

Purescript code calls into untyped code via its FFI for expediency or async integration constantly, for example.

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