You are currently looking at the v8.0.0 docs (Reason v3.6 syntax edition). You can find the latest manual page here.

Try via CLI

You can compile a file directly via bsc MyFile.re (or bsc MyFile.ml):

Reason (Old Syntax)ML (Older Syntax)
 
// MyFile.re
let rec fib = n => {
  switch (n) {
  | 0 | 1 => 1
  | n => fib(n -1) + fib(n-2)
  }
};
Js.log(fib(0));
SH
❯ bsc MyFile.re // Generated by BUCKLESCRIPT, PLEASE EDIT WITH CARE 'use strict'; function fib(n) { if (n === 0 || n === 1) { return 1; } else { return fib(n - 1 | 0) + fib(n - 2 | 0) | 0; } } console.log(fib(0)); exports.fib = fib; /* Not a pure module */

You can also get the inferred signature directly via bsc -i MyFile.re

Reason (Old Syntax)ML (Older Syntax)
 
let fib: int => int;