Mastering Time-to-Market with Haskell

---

> An effect is anything that invalidates some equational law that holds for values.

Ah, I can certainly accept that as a definition, except that I'm not sure how different it is from mine, because the equational law you refer to applies to syntactic terms (`foo` in your example) and the language's equality operator (`==` in your example). It's easy to come with an equivalence relation that would hold for `foo`, but not at the syntax level (e.g., equality that takes `foo` to mean `foo`'s definition and the content of the heap, and the value of `foo` would not be its return value but its behavior -- i.e., the behavior of foo for equal heap contents is always the same).

It wasn't. I simply stated that it's a negative signal; that's not FUD. It is a negative signal whether or not I mention it. Mentioning it gives Haskell advocates a chance to address it. You don't have to, but whatever you do, the signal is there. But it's just one signal. I don't think anyone should make a decision based on just one signal.

> Those interested in learning more about pure functional programming should try Haskell, the others have different niches they are trying to fill.

What should those interested in increasing productivity learn? This entire discussion isn't about learning a new programming style, but about achieving a goal of reducing development costs.

> No one is claiming Haskell is some sort of magic bullet for all use cases.

So what is the claim, and is there actual evidence (even anecdotal) to support it?

> I suspect that most of our industry isn't really interested.

The industry is extremely interested in anything that can significantly reduce the cost of developing software. We don't care if it's called Haskell or an omniscient debugger, or a static analysis tool.

> and will continue to be successful in that niche, with or without further productivity studies.

That's terrific, but don't blame the industry for being short-sighted and investing heavily in something that has little evidence of a great promise. You can only blame the industry for ignoring evidence, not for ignoring hype.

It's a level of attack reserved for a special level of unsupported hype. I have absolutely no problem with those who say they really like Haskell, it fits well with how they think, and they feel more productive with it. I even have no problem with those who say that they believe the language has objective benefits in some domains and circumstances and that it deserves a closer look. But if you go around claiming that we can significantly reduce the cost of software development using your language (or any tool), I think an intsy-bitsy amount of even anecdotal evidence is required, especially after two decades.

You may not believe me, but I truly admire Haskell's elegance (even though I believe pure-FP is not the right path for most kinds of software; I have my own pet hypotheses). I just don't like the religious ecstasy that surrounds it.

> and they don't seem willing to pay what it would cost to study these questions to a scientific level.

Because in order for a business to invest in a costly experiment, there should first be some evidence that there's a good chance for the experiment to pay off significantly. Businesses aren't research institution, and they can't afford to invest in researching every new technology that somebody really likes.

> anyone who does that runs the risk of being outcompeted by those who pick a better lanugage.

As soon as the competition pulls ahead, people will be quick to flock to the new language. That's what happened with late Java adopters.

> would come with a high risk factor.

You're right that the risk isn't nonexistent, but it's relatively low (and Kotlin is backed by a larger company than the ones backing most new languages, with the exceptions of Go, Swift and maybe Rust). There's automatic translation and seamless interop, and gradual adoption is very easy. You can pick a class at random and translate it to Kotlin to test if build/debug/profile/deploy etc. works well, and then translate more classes. I'm not sure such a tool exists, but it should be fairly trivial to translate Kotlin back to very readable Java if the need arises to revert for whatever reason.

> but the business incentives don't seem to be there for those early-adopter businesses to publish that kind of report

I think that the business interests are there. If you invest heavily in a language, you'd want it to gain wide adoption so you get more maintenance, more libraries, easier recruiting, more tools and lower risk. The business interests would not be there if Haskell provided an incredible boost in productivity, that is so large that the competitive advantage offsets the downsides of low adoption. I don't think anyone is even making that claim.

Productivity for whom? And over what timescales? As I have been trying to say, it is not that simple, you are oversimplifying.

> So what is the claim, and is there actual evidence (even anecdotal) to support it?

It sounds like you are completely satisfied with existing approaches, in which case there is little point in me trying to convince you.

> The industry is extremely interested in anything that can significantly reduce the cost of developing software.

Industry as a whole, does not have a good track record of adopting even good ideas in a timely manner. c.f. Garbage collection. So again, I think you are oversimplifying.

An effectful language can be given a denotational semantics. At least from what I've seen, when most people say “pure”, they mean “effect-free”.

> It's easy to come with an equivalence relation that would hold for `foo`, but not at the syntax level [emphasis mine]

Yep, indeed, that's the whole point.