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back in the days, I had this infatuations with the idea of having everything checked at compile time by using type system. and I see many people following this kind of path with type system of Haskell, rust, and maybe typescript. granted, it feels good, at first.

I don't do that any more. simply because I'm very lazy and also in a lot of cases, those types that I wrote will be replaced by more dynamic representation (e.g. strings) at some point.

discuss

ebingdom|4 years ago

> I don't do that any more. simply because I'm very lazy

I'm lazy too, but that's exactly why I use static types. So that when I refactor code, I can let the type checker tell me all the places that need to be updated instead of trying to piece that together from test failures (and praying that the tests didn't miss anything).

12thwonder|4 years ago

yeah, but my point is that checking system that you had created will be thrown away at some point in my experience. so why bother writing types? that is my attitude at least at very early stage of a project.

later in a project where you know for sure something can be known at compile time, of course I love to check them at compile time.

scns|4 years ago

Lazyness as the motivation for creating machines/typecheckers to do the boring work.

ourcat|4 years ago

I'm still in the 'feels good' stage with meticulously modelling the types of data I use in Angular with Typescript.

Initially, I couldn't really see the point, but if anything I find it helps with catching errors and response expectations before build-time and also auto-completion/pseudo-documentation/hinting in VSCode.

Now, I love it.

iamevn|4 years ago

> in a lot of cases, those types that I wrote will be replaced by more dynamic representation (e.g. strings) at some point. I would love to see a type system that lets me subtype string, restrict the domain, and automatically (with some hints from the programmer) get functions on my type based on string functions the compiler can prove would result in my type.

I've only seen type systems that work like this on numbers, and usually only a very few integers at that.

jkhdigital|4 years ago

The formal notion of subtype seems to be getting some solid research attention; see e.g. https://drops.dagstuhl.de/opus/volltexte/2021/13888/pdf/LIPI...

Hopefully we see these ideas make their way into functional languages soon.

dboreham|4 years ago

That laziness isn't so smart when it comes time to write all the tests to check there won't be runtime exceptions due to treating values as the wrong type.

scns|4 years ago

In TypeScript you can define your discriminated union with strings, they call it literal types:

  type Foo = "bar" | "baz" | "qux"