How to get a random element in a given List in Elm?

Question

I'm building a sliding puzzle game:

From this initial position, I'd like to shuffle the puzzle, say 100 moves.

I'd like the puzzle to be shuffled differently each time.

This probably means that I need to call Random.initialSeed with a different number every time, which means that I need to use something like the current time.

Unfortunately, I couldn't find how to get the current time.

In every given state, I have a list of possible moves. For example, in the initial position above: [MoveRight, MoveDown]

So, basically, my question is: how to get a random element in a given List?

share-elm example would be appreciated.

Answer 1

Rough answer (not near a compiler right now):

If you want to vary the seed based on the current time, add Time.every to your signal graph:

http://package.elm-lang.org/packages/elm-lang/core/2.1.0/Time#every

Keep the last seen timestamp in your model, then, when you need to shuffle, use it to seed your random. Generate an integer in the range [1, length list], and then pick the element of that index.

Hope that's enough of a hint, please yell if it isn't and I will elaborate when I get chance.