It isn't interoperable with Ruby and I don't know of any reputable companies using Crystal.
It just looks like Ruby, but it isn't Ruby and it is a compiled language? OK?
I am not sure why I should learn this language?
Kagi uses Crystal for their search backend [1]. How they feel about that today and whether that was the right call are, of course, separate questions.
[1] Previous thread: https://news.ycombinator.com/item?id=38421149
Did you forget that until five minutes ago humans used to read the code? And they needed to understand it? Yes, there was an actual desire for great Ruby-like syntax without the implications of using it, like its performance characteristics and the need for an interpreter.
Yes, it didn't go mainstream. Should we all abandon every project we've ever worked on because they're not "relevant"?
My message to the HN community: HN is literally bankrolled by YC. If Crystal doesn't deserve to exist because other languages exist, why exactly should I care about your bullshit uber-for-dogs startup, or whatever not particularly original AI crap you think you're changing the world with these days? Get real. If you want people to be open to your ideas, maybe you ought to make an effort to be open to the ideas of others, and cultivate a climate where discussing different ideas is possible. Don't treat every HN post as an opportunity to opine on how you think the work of other people is flawed.
You should learn this language if you want the nice developer experience, great stdlib, managed memory, native performance. Similar reasons to why you'd learn Go.
LLMs though - I confess they've changed the calculus. Now I no longer have to look at the language, and obey its stupid ideas about error handling, I just use golang for its better library support. But I still have a soft spot for Crystal!
It's close enough that porting things is often trivial (sometimes just slap a few signatures), as long as the code doesn't go crazy with metaprogramming. Yes, it's not the same and stdlib is a bit different. But it's a lot further than "looks like" Ruby.