jh29awhich languages have a REPL and Type Annotation?
PencilnoobYes, F# is such a sleeper hit language. Basically Ocaml++ with a bunch of cool extra goodies. Open source, high performance runtime and tons of great libraries.
I’ve been using it at work and it’s excellent
If only it had the one thing of OCaml does that’s actually important: ML modules.
Okay, I’m being kinda glib. Ocaml has plenty of other stuff going for it, and F# is a great, productive language, but its biggest weakness is something it doesn’t have.
What’s the big thing that enables, I’ve played with so many languages but I’ve never actually used OCaml enough to understand that feature
Modules are called such because they enable modularity. pathsensitive.com/…/modules-matter-most-for-masse… that link will explain it more thoroughly than I want to or probably could.
Ah ok, we’re getting into Coq proofs. I’m trying to work through Software Foundations but it’s so tricky! I feel like I need an intellect potion to get it
That, or Haskell’s typeclasses (which serve much of the same need). Without one or the other you lose out on a lot of expressive power.
Modules are substantially more expressive than typeclasses, but yes, type classes get you most of the way there.
They have different sets of tradeoffs and prioritize different things. Nevertheless, you can express typeclasses with the module system just as you can express the module system with typeclasses (using modern Haskell language extensions to the typeclass system). One is not more expressive than the other. You give me any usage of the module system, and I can show you how it can be done with typeclasses.
Hah, I was afraid you would say that when I wrote my comment. I don’t mean expressive in the sense of “can encode X”; I mean expressive in the sense of “can nicely encode X”. The bullshit you have to put yourself through in Haskell to get the core niceties of modules is unpalatable (to me, anyway).
C# : Does it have a repl?
As a procedural language (though it’s becoming more and more functional-like with each release) C# isn’t exactly designed to work with a REPL, but I think Visual Studio (the IDE, not the text editor) comes with an immediate window that works as one, and a quick internet search finds many third party ones, like .NET fiddle for the web, or CSharpRepl for the command line.
I guess, Python technically counts, although the type annotations were one hell of an afterthought.
I do feel like the two features are somewhat at odds with each other.
A REPL is useful for quickly trying something out, which you’d typically use to put together a quick script. In a larger application, you generally want to define unit tests, which make your “quickly trying something out” reproducible and automateable.
Meanwhile, type annotations primarily start to shine in larger applications, where you cannot keep the whole context in your head and where refactorings become problematic, when nothing checks that the parts still work together.
In some sense, they also don’t work well together. Type annotations work best when the whole context is known. But in a REPL, you almost always have an incomplete context, because you’re still typing everything out.
So, it cannot type-check the first few lines you write and it becomes awkward to try to show type errors once the context is complete, because the code isn’t on-screen anymore.
Rust has a repl: github.com/evcxr/evcxr
JackbyDevJava has JShell. It comes with the JDK. docs.oracle.com/en/…/introduction-jshell.html
Java Shell User’s Guide
The Java Shell tool (JShell) is an interactive tool for learning the Java programming language and prototyping Java code. It was introduced in JDK 9. JShell is a Read-Evaluate-Print Loop tool (REPL), which evaluates declarations, statements, and expressions as they are entered and immediately shows the results. The tool is run from the command line.