+ operator to create sequence of actions

[jcornaz]

I think a + operator to easily create a sequence of actions would be nice

Example:

val sequence = moveTo(200f, 200f, 0.5f) + rotateTo(90f, 0.5f) + fadeOut(0.5f) + remove()

[czyzby]

It could be similar to then infix method, but it should not mutate sequence actions.

[jcornaz]

It could be similar to then infix method, but it should not mutate sequence actions.

Ooops, indeed I forgot about then.

However I personally think that + and then should do exactly the same. (and not mutate the receiver)

Using then or + would only be a style choice (like using crs or x with vectors)

But a += may mutate the receiver.

val sequence1 = moveTo(200f, 200f, 0.5f) + rotateTo(90f, 0.5f) + fadeOut(0.5f) 
val sequence2 = moveTo(200f, 200f, 0.5f) then rotateTo(90f, 0.5f) then fadeOut(0.5f) // should produce the same result as above

sequence2 += remove() // One could still mutate a sequence like this

EDIT: Let me also argue that the then infix functions overload is currently inconsistant:

• Action.then(action: Action) does not mutate the action
• SequenceAction.then(action: Action): SequenceAction does mutate the sequence

[czyzby]

These are valid points. I believe when I was implementing this, I was in the LibGDX mindset of trying to go easy on the garbage collector, but I agree that idiomatic Kotlin approach is better in this case.

[czyzby]

Thanks for your contribution @jcornaz. I just realized parallelTo has the same mutability issue. I'll change it similarly to then. Do you think it makes sense to add an operator for parallel actions? I'm afraid it would be less obvious than in case of sequences, but % or / could work.

[jcornaz]

Do you think it makes sense to add an operator for parallel actions? I'm afraid it would be less obvious than in case of sequences, but % or / could work.

No. I don't see the point of a non-obvious operator for parallel actions. In this case parallelTo is fairly enough.

[czyzby]

| would be more obvious, but it's not available in Kotlin 1.3.