Reasonml has pattern matching in specific syntaxes and one of those syntaxes is the
fun operator which helps you define multiple patterns for single argument functions.
let something = fun | "hello" => "world" | "busta" => "rhymes" | x => "something else"
something("hello") /* results in "world" */
This doesn’t work for multiple arguments however, so when you see something like this:
let add = fun | (1, 1) => 3 | (x, y) => x + y;
just remember that the single argument in this case is a tuple, called like this