Julia
is really impressive. So, I uh, was working on a julia implementation of unums till I stopped being funded for it...
I'm currently writing unit and continuous tests for a computer chip that is being simulated - basically julia does the computation in x86, which suggests what the IEEE result should be, and then generates the assembler and passes it on to the assembler.
It probably could have been easily written in something like python, ruby, or perl, but the modularness of Julia, functional programming, and (optional) explicit typing result in easy-to-read code and a sense of security that there are no shenanigans going on under the hood with the type system.
Another cool thing is for more complicated code (working on a demonstration fast fourier transform) is that I can write the core FFT algorithm as a function with macros, and by swapping a different include that defines the macros differently, it can either run it as a virtual processor using internal Julia arrays that represent the memory and register files, or build up a file that contains the assembler code. Again, this is obviously possible in other languages [0], but Julia makes it look nice and easy to comprehend.
[0] I'm thinking that ruby (especially with it's DSL-eyness) would be really good for this, but I abandoned ruby when it became too difficult (I'm lazy and dense) to install the correct version on my own computer much less figure out how to install it on a server for other people to use.