// 1. Functions can be considered a form of data!
//    How to describe their type? Signature! That is...
//    What data type(s) they take in, what data they produce

fun addNums(a: Int, b: Int): Int {
    return a + b
}

fun multNums(a: Int, b: Int): Int {
    return a * b
}

fun outputResult(a: Int, b: Int, operation: (Int, Int)->Int) {
    val result: Int = operation(a, b)

    println("Result: $result")
}

// outputResult(3, 5, ::addNums)
// outputResult(3, 5, ::multNums)














// 2. Functions can *produce* other functions :)
//    Why? Sometimes you need information to "customize"
//    the pattern of instructions in a function.
// 
//    Note: generally we avoid (can be confusing), but
//          we often *need* to (e.g., a function is
//          constrained in what arguments it can accept).
// 

// represents hours till boarding
val flightBoards = 8

val aliceBuffer = 1
val bobBuffer = 3


// produces a personalized calculator based on your buffer time
fun makeBufferApp(myBuffer: Int): (Int) -> Int {
    fun myBufferApp(whenFlightBoards: Int): Int {
        return whenFlightBoards - myBuffer
    }

    return ::myBufferApp
}

val bobBufferTime = makeBufferApp(bobBuffer)

println("bob: ${ bobBufferTime(flightBoards) }")
// println("bob: ${ bobBufferTime(12) }")
// println("bob: ${ bobBufferTime(4) }")

// and if we are only going to use it once, could...
println("alice: ${ makeBufferApp(aliceBuffer)(flightBoards) }")