Although SML is such a beautiful and pragmatic language and has many Compilers and Runtimes, I am not aware of any real world projects with impact other than the well-known SML compilers (Mlton, SMLNJ, MosML, Poly ... to only name a few).

Usage of SML results in very short, readable and efficient programs, so I wonder why there is only so little industry adoption.

Most of the people who would be using SML are using Haskell, hence why Robert Harper is so bitter, constantly writing blog posts about how much "Haskell sucks", and how "unsafe" it is.

edit: or OCaml, or F#.

I'm not sure it is right to speak of "most people". Many people use OCaml these days. For instance, I have the impression that in work on program verification and static analysis OCaml is more popular than Haskell. Coq is written in OCaml, for example. The Haskell community much more vocal though.

Harper has strong opinions, but he has a few points. Haskell may be great, but one should be aware that it is not an improvement on SML in each and every respect. For example, SML has a much better module system than Haskell.

Haskellers complain about Haskell's module system and say that SML's is better more often than any MLer, I think.

F# might already be more popular than both, but it's hard to tell for sure.

Yes, that's my point. We shouldn't say that most people use X because it doesn't seem clear cut at this point.

It's not really an ethical problem, just an estimation. If SML was the only similar language, surely a lot more people would be using it.

Perhaps OCaml gets a lot of use in that community because a lot of that community is French -- that was my experience, anyway. And a lot of the folks in that community don't seem as vocal (to this side of computing) only because they are using different channels and complaining about different stuff!

It was actually surprising (and somewhat annoying) that Twelf is written in SML.

adaption of ML style languages suffers from the unfamiliar syntax, the pretty steep learning curve for those trained in imperative dialects at 'java-school'.

at least when it comes to syntax mythryl might someday provide an option. its basically SML/NJ with a c-like syntax and multithreading support. still very much in development but looks promising: mythryl.org

that said Haskell certainly seems to be the winner of the current functional language trend.

I don't think people really care about syntax that much. OCaml, F#, Haskell all have similar looking syntax, Scalla has a particularly ugly one (maybe if it wasn't supposed to be C/Java-like it wouldn't have ended like this).

...the only times I heard people bitching about syntax to the point of staying away from a language for it was either about Lisps ("undistinquishable paren soup") or about Python's significant indentation and lack of multiline lambada. MLs have a pretty familiar math-like syntax and apart from some operators seems "normal looking" even for Java and C programmers.

I often use SML for writing games. The Functioning library (http://github.com/robsimmons/functioning) provides support for SDL and includes an SML port of Box2D.