pattern_matching.ml

(* OCaml *)

type person = {
  name: string;
  age: int;
}

let happy_birthday user = match user with 
  | Some person -> String.concat " " ["Happy Birthday"; person.name]
  | None -> "Is not logged"

let lucas = {
  name = "Lucas";
  age = 28;
}

let option = Some lucas

let _ = happy_birthday option

pattern_matching.re

// ReasonML

type person = {
  name: string,
  age: int,
};

let happy_birthday = user => {
  switch (user) {
  | Some(person) => "Happy birthday " ++ person.name
  | None => "Please login first"
  };
};

let user = Some({name: "Lucas", age: 28});

print_endline(happy_birthday(user));