Purity

Today, I had an idea.

LLVM has this really annoying verification function where when it fails, it dumps an error to stdout and then terminates the process. This is super irritating, partly because if Wide is, say, running as part of a VS extension, then there's nobody to see that error.

The key here is that the guy who wrote that part of the LLVM code made an assumption. He made an assumption about how the library would be used- as part of a command-line application. This assumption is obviously bad. This is why for Wide I'm choosing to restrict stdin/stdout/stderr.

But what I suddenly realized is that this is a vague match for that endless purity bullshit the Haskell guys like to spew. The libraries should not perform I/O for themselves, but only request data from higher up. Only the final driver author knows how the final product is used. He knows whether it's a command-line app or a VS extension or a web service or library for someone else to consume arbitrarily.

The problem seems to be that they simply express why things should be this way for totally the wrong reasons. Instead of shitting around about currying or mathematically correct functionality or some other random thing nobody cares about, they should get to the real reason why restricting I/O and side effects is a good thing- because it makes programs more maintainable and helps enforce separation of concerns. If they just gave an example like that, it'd be way easier to buy in.


On the level of implementing any given function, I tend to use mutability a lot. But on the level of interface design, I'm increasingly trending towards immutability, purity, and a bunch of other things.

I'm definitely still not feeling positive towards Haskell, though. Too much wankery, too little choice. Purity and immutability are tools, nothing more, and they are to be applied to the right situations, and nowhere else. Being forced into them is no better than being forced into using inheritance for everything in Java. But hell, if you made a Haskell where you could mutate function-local variables, I might start buying into that shit.