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
  • Compile-time meta-programming
  • 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.

See the examples directory for more.

  • Mutable types
  • Types across modules
  • Allow explicit types that have type parameters
  • Standard libary
  • Tail recursion