foo {
  $number: random();
  foo: $number >= 0 and $number <= 1;
  $number: random(1.0);
  foo: $number >= 0 and $number <= 1;
  foo: random(1) == 1;
  foo: type-of(random()) == number;
  foo: type-of(random(1)) == number;
  foo: type-of(random(1.0)) == number;
}