John Carmack: Thoughts on Haskell [video]

> Error establishing a database connection

Diabolic, stateful database connections blocking a Haskell treatise! They should have copied the database on each request instead.

I'm still waiting for his in depth article about his experiences while porting Wolfenstein to Haskell - mainly to see if it's worth learning Haskell. Beacause as he said in the video: Most examples in books (I guess that counts for evangelization blogs too) are toy examples. And I'd like to know how viable the language is for bigger systems.

Google cache: http://www.google.ca/search?q=cache:functionaltalks.org/2013...

The article is essentially just a link to the fourth part of his keynote at Quakecon ( http://www.youtube.com/watch?v=1PhArSujR_A )

This is highly anecdotal, but I've built and been part of very practical/non-theoretical, large Haskell projects (100k+ lines, which is a lot for Haskell). The only big complaint I have is that it's somewhat hard to do loose coupling, i.e. for something somewhere to reference a type without either redeclaring the type (when that's possible), or having a huge, centralized Types.hs that declares all the types that are used in different places (to avoid cyclic imports.) (Contrast with e.g. Go or ML where you have interfaces/modules without 'implements'.)

This isn't unique to Haskell by any means, but it's the only real complaint I have about Haskell as a language for non-toy projects. The benefits definitely make it my go-to language. It's hard to list them all, but by far the nicest feeling is the correctness: when your code compiles, 60% of the time your program works every time. (Not to imply that tests aren't necessary--QuickCheck is great for that.) It's an otherworldly feeling to write a program not in terms of what to do, but what kinds of filters you want to put on something, and have it just work (and either stay working, or break future compiles if something's changed!) after compiling 10 lines of code, when you would have written at least 50-70 and had to debug it in almost any other language.

Edit: I'll add another complaint: Haskell is like C++ in that it's incredibly easy for a codebase to become completely unmanageable if your team doesn't have a common style/discipline. Go is a nicer language for "average"/"enterprise" teamwork, I think, since it almost forces you to write programs in a way everyone will understand. If you're in a team with good programmers that you trust not to abuse the language, this is a non-issue.

Edit: Okay, another one: If you change your Types.hs, the recompilation can take a long time in a large codebase, similar to C++. But GHC/Cabal keep getting faster.

Think that's it.

I don't really get the joke. Generally functional languages will share more data than imperative languages, and therefore will copy less data. In an imperative language, it makes sense to copy whatever data you are working on, so your modifications don't inadvertently affect other parts of the program. In Haskell it doesn't.

Explain?