# Introduction to Swift

Apr 24 2024 · Swift 5.10, iOS 17, Xcode 15

## Lesson 02: Flow Control & Functions

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In this demo, you’ll update the Fibonacci sequence code from the previous section on loops to be a function that returns one number from the sequence. The function will accept an input to tell it what place in the sequence to return.

``````func getFibonacciElement() {

}
``````
``````var fibonacciSeries: [Int] = []

for index in 0...10 {
if index < 2 {
fibonacciSeries.append(index)
} else {
let element1 = fibonacciSeries[fibonacciSeries.count-1]
let element2 = fibonacciSeries[fibonacciSeries.count-2]
fibonacciSeries.append(element1 + element2)
}
}

print(fibonacciSeries)
``````
``````func getFibonancciElement(at inputIndex: Int) {
``````
``````getFibonacciElement(at: 5)
``````
``````for index in 0...inputIndex
``````
``````getFibonacciElement(at: 11)
``````
``````func getFibonancciElement(at inputIndex: Int) -> Int {
``````
``````return fibonacciSeries[inputIndex]
``````
``````print(getFibonacciElement(at: 11))
print(getFibonacciElement(at: 5))
print(getFibonacciElement(at: 1))
print(getFibonacciElement(at: 0))
``````
``````print(getFibonancciElement(at: -1))
``````
``````if inputIndex < 0 {
return 0
}
``````