mirror of https://github.com/roc-lang/roc.git synced 2025-11-03 06:02:54 +00:00

Richard Feldman 1993cd336b

Thank you so much, Peter! 💜

Signed-off-by: Richard Feldman <oss@rtfeldman.com>

2024-09-12 09:11:04 -04:00

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Roc

A fast, friendly, functional language.

credits = List.map songs \song ->
    "Performed by $(song.artist)"

Fast

Roc code is designed to build fast and run fast. It compiles to machine code or WebAssembly.

What does fast mean here?

Friendly

Roc's syntax, semantics, and included toolset all prioritize user-friendliness.

What does friendly mean here?

Functional

Roc has a small number of simple language primitives. It's a single-paradigm functional language.

What does functional mean here?

Try Roc

You can try Roc using this read-eval-print loop (REPL), which is running in your browser in WebAssembly.

Shift-Enter adds a newline.

Try entering 0.1 + 0.2


          Enter an expression to evaluate, or a definition (like x = 1) to use later.

Examples

Roc is a young language. It doesn't even have a numbered release yet, just nightly builds!

However, it can already be used for several things if you're up for being an early adopter—
with all the bugs and missing features which come with that territory.

Here are some examples of how it can be used today.

Command-Line Interfaces

main =
    Stdout.line! "Hello!"

You can use Roc to create scripts and command-line interfaces (CLIs). The compiler produces binary executables, so Roc programs can run on devices that don't have Roc itself installed.

As an example, the HTML for this website is generated using a simple Roc script. You can see the code for it in the main Roc code repository.

If you’re looking for a starting point for building a command-line program in Roc, basic-cli is a popular platform to check out.

Web Servers

handleReq = \request ->
    Task.ok { body: … }

You can also build web servers in Roc. basic-webserver is a platform with a simple interface: you write a function which takes a Request, does some I/O, and returns a Response.

Behind the scenes, it uses Rust's high-performance hyper and tokio libraries to execute your Roc function on incoming requests.

For database access, roc-pg lets you access a PostgreSQL database—with your Roc types checked against the types in your database's schema.

Embedding

fn = require("foo.roc");
log(`Roc says ${fn()}`);

You can call Roc functions from other languages. There are several basic examples of how to call Roc functions from Python, Node.js, Swift, WebAssembly, and JVM languages.

Any language that supports C interop can call Roc functions, using similar techniques to the ones found in these examples.

Most of those are minimal proofs of concept, but roc-esbuild is a work in progress that's used at Vendr to call Roc functions from Node.js.

Other Examples

You can find more use cases and examples on the examples page!

Code Sample with Explanations

Here's a code sample that shows a few different aspects of Roc:

File I/O and HTTP requests
Pattern matching for error handling
JSON deserialization via type inference
Common syntax sugar: pipelines, the ! operator, and string interpolation

The tutorial introduces these gradually and in more depth, but this gives a brief overview.

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Roc