[matt_m]

For fun, Scheme/Lisp. Once you have macros it really feels like the sky is the limit in terms of what you can express.

I've also been liking Go quite a bit recently. I know it's a language HN loves to hate. It's not as expressive as some other languages. But I feel like creativity within constraints can also be rewarding (kind of like writing a haiku). If I can find a way to reformulate my problem so that it can be expressed easily in Go, I'm often happy with the result. And because the abstractions Go provides are not very costly, it usually executes efficiently too.

It's hard to find a language that combines high level features with the lower level features that performance-sensitive apps often need (like value types, control of memory layout, etc). Also GC simplifies a lot of things, and Go makes it practical for a wider class of applications with sub-ms pauses and making it easy to minimize allocations. C++/Rust involve more programmer effort around ownership, and C# can also involve more programmer effort since minimizing allocations is trickier and GC impact is greater. It's not a big language but the combination of features / trade offs seems really practical.

Go's also widely used enough where you don't need to worry about having a robust library if you need HTTP2 or something.