"I would like to challenge that by pointing out that not a single piece of large software ... has ever been written using the skills/concepts of the higher levels of this chart."
To which I gave two counterexamples (today and on other occasions). All software systems should be modular to some degree, so I am not clear exactly what your criteria for a large software system is. In both my examples, the Haskell codebases are monolithic repositories where everything is typed-checked and built together.
You keep asking for quantitative data for a comparison with other languages. But my answer is the same as last week. It's good people that make software efficiently and cheaply. Give engineers PHP and they'll still manage to build something good. Haskell is just a tool, but it's a tool that increasingly good people are asking to use. The system at Barclays and Standard Chartered were built and are currently maintained very cheaply because good people were hired. Haskell just happened to be their preferred tool.
Let a "software system" mean any assembly of processes that communicate to provide some shared functionality, with the components being coupled to one another in some non-trivial way (i.e., there are correctness conditions that cross processes boundaries, so that changes to one program may necessitate changes in others). Excluding the compiler, how many lines of Haskell code do you have in your largest system (using my definition)?
Oh, thank god, finally we get a number. It turns out that I was completely wrong, and that in its 20 years of hyped existence, someone has built something big with Haskell once. You may think I'm sneering, but only a little bit, because while one is almost nothing, it is much better than actually nothing because at least it is a first anecdote. Now, who do I have pester to get some more metrics?
> More details here:
Sadly, there are no more relevant details in that talk.
Low cost of adoption + clear minor tooling benefits is usually enough evidence to adopt Java/C# style static types.
Haskell style static typing has a very high cost of adoption and so must conclusively show a strong benefit in order to be adopted by industry.
At the moment I feel Haskell companies can get away with using Haskell because PL enthusiasts are willing to absorb the training costs.
I am, however, very skeptical of the interpretation some people, especially in typed FP, give to types and the reasons they believe types provide a benefit. For example, the relationship between useful type systems and software correctness is not direct. I am currently using a formal verification tool that is completely logic based (and it has an interactive theorem prover, a model checker, and is backed by decades of careful mathematical analysis of its soundness) which is completely untyped, and yet it is as powerful as Coq for proving correctness of algorithms. If direct, formal, proofs of correctness is what you're after, types might not be the best solution. Types, however, have other clear benefits that are not related to formal correctness, or, at least, not correctness of global program properties.