Isn't it a waste to run a test suite for a program that would run 1M times a day in production?

The key adjective here is successfully run. You want to detect any errors as early as possible. Ideally even at the early stages of writing the script, when a typechecker is already able to point at certain errors, and thus help avoid missteps in further design.

> Isn't a waste to essentially reinterpret an entire program that may be run 5000 times a day?

This is a dated prejudice that I shared.

To get started coding with AI I made a dozen language comparison project for a toy math problem. F# floored me with how fast it was, nearly edging out C and Rust on my leaderboard, twice as fast as OCaml, and faster than various compiled languages.

Compiling could in principle be fastest, if we had compilers that profiled hours of execution before optimizing code, and only then for "stable" problems. No one writes a compiler like this. In practice, Just In Time interpreters are getting all the love, and it shows. They adapt to the computation. My dated prejudice did not allow for this.

I script with Rust via cargo-script, it works great. Scripting is a task for when you want to achieve something in one file instead of a full blown application. It is not about the language, you can script in C or assembly if you so chose.

"Scripting" is a role: an embedded, human-friendly, compact language, also suitable for interactive work / REPL.

(Laugh all you want, but Haskell has a rather nice REPL, and can work as a scripting language.)

Luau gets pretty close to statically typed and AOT compiled now. It's still a scripting language.

Even C or Rust can be a scripting language. You just integrate the toolchain to your app, same as every other scripting language.

The why: because Lua, Python, JavaScript, Janet, etc lack many or all these features. And each of these features is known to make life easier for a human programmer.

The reason it exists is to provide those features when programming computers.