Have banned methods return a new Immutable instance instead

Hi,

I love the fact that this library is super small and that doesn’t try to do anything else than making your data immutable 😃.

There’s only one thing holding me back from using it though:

Immutable([3, 1, 4]).sort()
// This will throw an ImmutableError, because sort() is a mutating method.

Have you considered returning a new immutable structure with the sorted array instead? (the same applies for every other banned method).

Thanks 😃 Darío

[rtfeldman]

I considered it, but the trouble is that doing this can mask bugs. For example:

function foo() {
  var array = [3, 1, 4];

  array.sort()

  return array;
}

If you change that first line to be Immutable([3, 1, 4]), what should happen?

Currently array.sort() throws an exception, letting you know that some code that made sense with a mutable array no longer makes sense. If instead array.sort() just returns a sorted, immutable array, then now an unsorted array will be returned here, and you have a bug to track down - a potentially nasty one, if there is a lot of logic surrounding this code.

I prefer this API because you can take an immutable array and write any number of helper functions that return sorted ones, but the only way to make bugs like this easy to find is to override the mutable methods to throw an exception. 😃

[nin-jin]

You can add method sorted(fn) that returns sorted copy of array.