Until you encounter a real Lisp implementation that contains an actual thorough, well specified and bug free implementation of type system more powerful than the one Haskel has.
Interested? Then take a look at the Shen[1] and enjoy having both the benefit of types and other powerful Lisp constructs in one language.
Is anyone using Shen yet? The only problem, and I am a passive lurker in circles in HN, Reddit, and elsewhere it has been mentioned, is an Ocamlesque license policy. People have said this will get them nowhere. It is understood they, from the outside view, want a single language implementation, not just a standard. But everyone I see says they will not touch it with a ten foot pole for this reason.
Also ironically, this real implementation of Lisp necessitates being built on "lesser" or not "real lisps" for us commoners, like SBCL and CLisp. It also has hosts on Ruby, Python, and this even lesser lisp called "Scheme" (rest assured, this is a joke and not a troll).
Indeed, the license is impossible. In addition to what you point out, it attempts to say the same thing as many as 5 times, introducing unacceptable ambiguity.
The final straws for me is that it is the creator's explicit intent that no incomplete or incorrect implementations be publicly accessible (he among other things thinks there's enough already...), and that the author broke a promise to the community, demonstrating that his word is no good.
I am confused about all these licensing "problems" everyone is talking about here. Could you enlighten me?
Sure, Ocaml and shen have "weird" licenses but I just read through them in the last few minutes and see no major issues.
The licenses for both only effect the code for the language interpreter/compiler and associated libraries itself and should have little to no effect on your own code.
If you use MIT/BSD licenses then you are almost certainly fine, with GPL there are some potential issues but most people think that dynamic linking doesn't count as "linking" in the lawyer sense and, therefore, using GPL code with something like Shen would be fine. This hasn't been tested in the courts AFAIK.
The problem you haven't noticed is that the language covering what you care about, using Shen to write programs, is in many places (potentially at least 7 by a count I just made), and you, or, say a lawyer for your company, has to read and understand the whole huge thing to make sure your intended use is OK. And that the multiple times it tries to say the same thing are not ambiguous.
It's also explicitly not open source ("We are therefore not open source."), and should you find yourself needing to fix a bug in a language implementation your legal burden massively increases.
Compare this to the licenses you name, they're all well understood, and in at least some cases validated in court. For that matter, the GPL has been validated in at least US and German courts.
As for Ocaml, it uses the Q Public License (as well as the LGPL); it's short and a quick glance didn't indicate it tries to say the same thing more than once. It's been around for a while, to the point it's an OSI and FSF approved licence, so others have looked at it, as they did for Qt prior to version 4.0., and KDE based on it prior to then. About which there was much todo, so it's be thoroughly analyzed.
So it may be "weird", but it's significantly more palatable than Shen's license.
To qualify my original statement much later, I was told offhand by people Ocaml's multi-core processor/SMP limitations continue to exist (I know Jane Street actually is putting up money to change this) because the license of Ocaml prohibited people from making any other forked implementation of Ocaml itself. Thus, it has been single-core only for many years later, because Xavier and the core team did not think SMP implementation was a priority, and have not been asked since.
Granted, I very seemingly little about this. So I could be very mistaken. Can some confirm I am wrong? I am sure someone here has far more detail than me generalized nonsense.
Yes, it's a pity it has such a license. People tend to dismiss it without even looking at it because of the license.
I don't think the language will take off unless it change licensing before it's too late, but I still find it enjoyable to use with some smallish projects.
I hope that Shen will get a successor that will make it more suitable for modern world while keeping ideas that make it unique and sound in the first place and smoothing the rough edges.
I would love to use Shen, but I refuse. Clojure's license is restrictive enough (I can't write GPL projects in it). But Shen isn't even free software by any definition.
In order to package a Clojure project, I have to include clojure.jar which is an EPL licensed project, incompatible with the GPL. If I write my code in Clojure, but license it under the GPL, then that forces me to not package clojure.jar with it, making the installation process a huge pain.
I'm pretty sure that isn't a surety. See the accepted answer here https://stackoverflow.com/questions/11412160/java-libraries-... for instance. LGPL, in any case, would almost certainly be okay. Most people I talk to consider .jar's a dynamic link and dynamic links okay via the GPL but there are alternative interpretations and I don't think it has been tested one way or another in the courts.
Shen has the same problem as Idris and all the rest of the languages with more powerful type systems than Haskell: none of them are ready for production use. I would absolutely love to be able to work in a more powerful type system, but the support just isn't there yet. Hopefully we'll get there in the next 5-10 years, at which point I will very happily switch over.
