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0 pointsmrkeen2y ago0 comments

Yeah I can't really follow these threads.

I saw:

> What's the benefit of learning a PURE functional programming language, opposed to just using a language which has adapted the best bits and pieces from the functional programming paradigm?

I also saw:

  Though you can break purity with just inputs:

  define f(o): return o.x
  let a = {x=1}
  f(a)
  a.x = 2
  f(a)

I don't know if that's the tail-end of a reductio ad absurdum which is trying to demonstrate the opposite of what it stated. Either way, to be clear, the above would be rejected by Haskell (if declared as a pure function.)

I guess if you learn a functional language "which has adapted the best bits and pieces from the functional programming paradigm" then you might think that the above is broken purity, but if you learn a "PURE functional programming language" then you wouldn't.

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Dylan168072y ago

The topic is what you would learn from a pure functional language.

A) You can learn and enforce full purity in other languages. B) You could also learn and adapt just the idea of clean inputs and outputs to those other languages.

Both of those are valid answers! It's very hard to be completely pure if you're not currently using Haskell.

The way they worded things, I wasn't sure which one they meant. They were describing option B, but I didn't know if that was on purpose or not.

So I responded talking about both. Complete purity and just the idea of clean inputs and outputs.

That code snippet is not some kind of absurd argument or strawman, it's there to demonstrate how the description they gave was not a description of purity. It's not aimed at the original question.

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