Small functional language that compiles to JavaScript


Roy is a small functional language that compiles to JavaScript. It has a few main features:

  • Damas-Hindley-Milner type inference
  • Whitespace significant syntax
  • Simple tagged unions
  • Pattern matching
  • Structural typing
  • Monad syntax
  • Not-horrible JS output

To compile:

make deps

To enter a REPL:


To compile and run a .roy file:

./roy -r examples/helloworld.roy

To compile a .roy file to .js:

./roy examples/helloworld.roy
cat examples/helloworld.js

Input (test.roy):

let addTwo n =
    n + 2
console.log (addTwo 40)

Output (test.js):

var addTwo = function(n) {
    return n + 2;

Calling addTwo "test" will result in a compile-time error (addTwo can only take a Number).

See the examples directory for more.


  • Roy website:
  • Roy Google Group:
  • Roy docs:
  • Roy Twitter:
  • Bitbucket repo:
  • GitHub repo:
  • Brian's blog:
  • altJS channel: irc://