I often hear about lisp but never actually figured out what tooling you need Is it interpreted or compiled language? Why should I use it instead of any other languages?
Perhaps the default choice is Common Lisp which itself is specified in an ANSI standard and has several competing implementations. Some are compiled, some are interpreted.
Arguably the best is SBCL, which has a mature compiler and garbage collection. If you lean on implementation-specific features you can produce extremely fast code that approaches the performance of C in some benchmarks, but idiomatic and portable lisp is slower in practice.
>Why should I use it instead of any other languages?
The killer feature used to be the REPL. You can write the application function by function, and test the functions, data structures, or classes you write in the REPL as you're actively building the app.
Nowadays with LLMs writing all the code, I honestly don't see much reason to reach for lisp. Agents don't require a REPL, and other languages have vastly superior library support.
and then use JUnit or TestNG in Java, or similar features in other languages. Which you can automatically run, including showing code coverage, both with a button in your IDE and as part of the CI/CD process when you commit.
If you've already thought out the whole program before you start writing it, that may not be as valuable. In my experience, software often isn't that way and the ease of exploration a REPL and long-running process provide are unmatched.
There is no reason you can have a REPL and unit tests in the same. Every change results in running all the tests. (of course most changes are syntax error - just "if foo()" is 7 syntax errors. ) I've seen various attempts of this over the years, but quickly your code becomes more complex than the computer can run while you type and you fall back to running most of the tests after in some way.
That does not match my experience with lisp.
For real world code in other languages I've worked with the complexity of the problems demands so much code that the REPL cannot keep up.
Now we disagree, at least in part.
REPL-driven development is in part about incrementalism. You wouldn't run all the complex code every time you want to examine some state or try out an experiment. You would run it once at the start of your session, then compile just the definition you're editing with your editor's equivalent of `compile-defun`.
Of course that breaks if you're making changes that touch a bunch of different areas of your program and require rebuilding all the state, but it's usually a mistake to design programs in a way that would make such an issue frequent.
I.e. you could execute a unit test in a REPL (after e.g. loading the test), but you can't run a REPL in a unit test - you can debug a test and maybe do some REPL like things, but, it's not the same at all...
You also can't write a unit test in a unit test, you can in a REPL.
Heck, an AI chatbot is a (non deterministic) REPL (it reads, evaluates, and prints something)...
Like others were saying, they are different, i.e. nothing at all alike, tests do not obviate REPLs...
The killer (hah!) feature is arguably its homoiconicity, allowing to modify the language easily within itself ("macros"). This has the obvious advantage that you can add missing features (usually) easily yourself; and exactly that causes headaches for those tasked with maintaining other people's code.
> Nowadays with LLMs writing all the code
Oh, you came all the way from the future and that's what you bring us?
If you're building products without LLMs today you're going to get outcompeted by people who do, and can iterate faster. I have written a fair bit of lisp and when it isn't refusing to fix security bugs because openai are cowards, 5.6-Sol can do in hours what would take me days.
I used the word "arguably" in the very first word of that sentence:
>Arguably the best is SBCL
The word arguable is a synonym for the word debatable.