type foobar = {foo: int, bar: int };

let fb: foobar = {foo = 0, bar = 0 };

type abc = {a: int, b: int, c: int };

let abc: abc = {a = 42, b = 142, c = 242 };

let a: int = abc[a];

let b: int = abc[b];

let c: int = abc[c];

let projection = (r: foobar): int => r[foo] + r[bar];

let modify = 
  (r: foobar): foobar => {foo = 256, bar = r[bar] };

let modify_abc = (r: abc): abc => {...r, b: 2048, c: 42};

type big_record = {a: int, b: int, c: int, d: int, e: int };

let br: big_record = 
  {
    a = 23,
    b = 23,
    c = 23,
    d = 23,
    e = 23
  };

type double_record = {inner: abc };

let modify_inner = 
  (r: double_record): double_record => {...r, inner.b: 2048};