F#: Storing and mapping a list of functions

dictionary, f#, function, list

Solution

Did you mean something like this?

let myActions =
    [fun () -> printfn "You've woken up a dragon."
     fun () -> printfn "You hit the dragon for 0 points of damage."
     fun () -> printfn "The dragon belches."
     fun () -> printfn "You have died."] 

let actionBuilder actionList = 
    let actions = ref actionList
    fun () ->
        match !actions with
        | [] -> ()
        | h::t -> h(); actions := t

Usage (F# interactive):

> let doSomething = actionBuilder myActions;;

val doSomething : (unit -> unit)

> doSomething();;
You've woken up a dragon.
val it : unit = ()
> doSomething();;
You hit the dragon for 0 points of damage.
val it : unit = ()
> doSomething();;
The dragon belches.
val it : unit = ()
> doSomething();;
You have died.
val it : unit = ()
> doSomething();;
val it : unit = ()
>

**Edit: ** if you want to be able to add actions, maybe it's better to make an action dispenser that uses a Queue internally, since appending is O(N) with a list and O(1) with a Queue:

type actionGenerator(myActions: (unit->unit) list) =
    let Q = new System.Collections.Generic.Queue<_>(Seq.ofList myActions)

    member g.NextAction = 
        fun () -> 
            if Q.Count = 0 then ()
            else Q.Dequeue()()

    member g.AddAction(action) = Q.Enqueue(action)

Problem

I have a number of events that happen in a game. I want to control the time and order at which these events occur. For example: Event 1: Show some text on screen for N frames & play a sound effect Event 2: Clear the text on the screen My solution (maybe there is a better one), is to have a list of functions that contain the events. The events perform their behavior then return the next events to occur in the game. I thought of using List.map or List.collect because I am essentially mapping a list of events to a new list of events while performing some behavior code. In the example above, Event1 can be composed of two functions: One that shows text and one that plays a sound (hence the need for a list). The function that shows text would return a copy of itself for N-1 frames then it would return Event2 which clears the text. The play sound function would return the equivalent of a no-op. If this is a good solution, I could probably do it in C++ or C#. My goal is to do an equivalent or better solution in F#.

Original source