Interesting examples of Domain Specific Languages

I'm considering doing something with Domain Specific Languages for my undergraduate project. My one problem is I can't really find any interesting examples that I can root around in. Does anyone have any good examples of DSELs (preferably open source)?

Also, one area I would love to look at is solvin开发者_运维百科g/addressing concurrency problems (coroutines etc) with DSEL's. Are there any good examples that anyone uses of this in DSELs? If this is a stupid application of DSELs please explain why...

Another potential area to explore would database programming. Again is this a stupid area to explore with DSEL's. For example, would adding some crazy database manipulation syntax to C# say be a good project to undertake?

EDIT: General languages I would be looking at implementing in would be Java, Python, Scala, C# etc. Probably not C++ or C.

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Linda implementations can be considered as eDSLs. STM implementations like CL-STM are certainly eDSLs.

Unrelated to concurrency, but extremely useful are embedded Prolog implementations, there are plenty of them for Scheme, Lisp and Clojure. Parsing eDSLs had been mentioned already - and their patriarch Parsec definitely worth digging into.

EDIT: with your list of implementation languages you're missing the most interesting eDSL opportunities. The most powerful and flexible eDSLs are made with metaprogramming. Scala-style (or even Haskell-style) eDSLs are based on high order functions, i.e., on mini-interpreters. They're more complicated in design, much less flexible and limited to the syntax of your host language.

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boost::spirit if you're after C++ is an interesting example. Quote:

Spirit is a set of C++ libraries for parsing and output generation implemented as Domain Specific Embedded Languages (DSEL)...

(I have no idea what you mean by "solving concurrency" though. I don't see how you can solve "concurrency problems" in general, or how a DSEL could help.)