Having trouble combining Vector::withMutations with Vector::splice

[nathansobo]

Should the following code example log true? On 2.0.4 it's logging false for me. Am I doing something wrong?

vector = Immutable.Vector(1, 2, 3)
a = vector.splice(1, 1, 'a', 'b')
b = vector.withMutations (v) -> v.splice(1, 1, 'a', 'b')
console.log Immutable.is(a, b)

[leebyron]

This is a bit subtle, but splice is not available as a mutative method. It always returns a sequence. Because splice needs to push the indices of the elements after it, it always needs to create a new vector.

I agree that this behavior isn't super obvious though. I think the code you wrote should have done what you expected. Unfortunately right now it doesn't. The answer is to (outside of withMutations) do vect.splice(...).toVector()

[leebyron]

This behavior is also made clearer by RRB, so now tracking this in #38