Take a look at this LINQ raytracer, discovered via Scott Hanselman's latest source code exploration post.
For those of you who don't know what the heck LINQ is, it was created as a language extension for .NET to allow querying of datasets using an in-place SQL-inspired notation. This was a huge step up from maintaining separate bodies of stored queries, or hard-coding and dynamically assembling queries as strings in your source code.
Lately LINQ has been enhanced and expanded upon even further to become a more broadly usable miniature functional/declarative language within .NET. This is impressively illustrated by the raytracer code. The author disclaims that it's probably not the best way to write it, which is probably true. But this in no way detracts from its illustration of the power, expressiveness, and flexibility of LINQ.
I love it! It's a great example of taking a deceptively simple language and showing its power by doing things with it that aren't strictly within the purview of its design. It reminds me of some SQL code that I've written for my current employer, to get functionality out of inefficient PL/SQL and into blazing-fast pure SQL. Stuff that it was said couldn't be done in pure SQL. Of course, this is usually said by people who think that SQL is a second-class citizen among languages, not realizing the power of its declarative foundations. This is something that I hope to write about more extensively in the future, either here or in a new SQL blog I'm considering starting with a friend and coworker.
Anyway, I'm tempted to say that there's a bit of a down side in that this LINQ raytracer is mostly comprised of LETs, which feel more imperative than declarative. However, I've long claimed that just such functionality in actual SQL would make it a tremendously more compact and elegant language, so I won't complain too much about that. =)
My gut reaction upon seeing this code is that it feels like a crazy hybrid of LISP and SQL, but it's written in C#. Which all makes my head spin, but in a good way. I love that C# is becoming such a great hybrid of procedural and functional programming paradigms.