[caltelt]

I was really excited when I started using racket that I could switch to static typing when I wanted it. However after trying out contract's, I must say I'm quite a fan of them as an alternative. Sure, you lose out on static, compile time checking, but honestly, I haven't missed it. And it's _even more_ seamlessly integrated into un-contracted code. You can express more interesting things and complex relationships between parameters using the ->i contract than any type system I know of will allow. There's some limitations, but between it and unit testing, I've been having a blast.

[smabie]

Contracts incur absolutely massive performance penalties. Sparingly used, they can provide value though.

There's no reason why you can't have types and contracts though. I personally can't live without compile time guarantees.

[zelphirkalt]

I've tried racket/typed before and my knowledge or experience with it might be outdated, but sometimes I just could not get it to agree with my code. I fix one typing warning or thing it cannot infer and another would pop up. I fix the other, then a third pops up. I try to fix the third one, but realize I cannot and need to go back to the original state. When such things do not happen, it is very cool though. The code behing typed racket for me seems so mind bogglingly complex, I did not dare to investigate further. It is a language composed of macros, which use rackets macrology stuff, which is already more complex than other Schemes'. That language can be used to design any type system as far as I read about it.

With my typing trouble I should have come to the user list and asked, but I dId not, frustrated and thinking I was too stupid to get it ^^'

I did once at least see a question on the mailing list, where the answer was, that typed racket could not do it, as in infer types, so it might not be perfect yet, or perhaps it did improve since then.

I wish more Schemes could just copy the typed part of typed racket, using that macro language, as in theory they should be able to represent it, but I guess the devil is in the detail and slightly different workings of macro facilities.

[smabie]

Racket has a much more advanced macro system than scheme's traditional syntax-case.

[zelphirkalt]

Yes, it certainly has, but I think it's still based on that traditional syntax-case stuff. So in theory other Schemes could perhaps copy it, if anyone can get all the macrology behind it. Also in theory it should be possible to express all the advanced Racket stuff in syntax-case.

Do you think it is not possible to express these things in syntax-case? And if so, why?

[kwhitefoot]

Not always. Quite a lot of contracts can be statically checked. Unfortunately the only contract checker [1] I have experience with is too slow to be useful on source code that is itself large enough to be really useful.

And in C# at least contracts can be disabled for release builds so that the performance penalty is only inflicted on the developers.

[1] https://docs.microsoft.com/en-us/dotnet/framework/debug-trac...