Swift 3 for loop with increment

Question

How do I write the following in Swift3?

for (f = first; f <= last; f += interval)          
{
    n += 1
}

This is my own attempt

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Answer 1

With Swift 5, you may choose one of the 5 following examples in order to solve your problem.

---

#1. Using stride(from:to:by:) function

let first = 0
let last = 10
let interval = 2

let sequence = stride(from: first, to: last, by: interval)

for element in sequence {
    print(element)
}

/*
prints:
0
2
4
6
8
*/

---

#2. Using sequence(first:next:) function

let first = 0
let last = 10
let interval = 2

let unfoldSequence = sequence(first: first, next: {
    $0 + interval < last ? $0 + interval : nil
})

for element in unfoldSequence {
    print(element)
}

/*
prints:
0
2
4
6
8
*/

---

#3. Using AnySequence init(_:) initializer

let anySequence = AnySequence({ () -> AnyIterator in
    let first = 0
    let last = 10
    let interval = 2

    var value = first
    return AnyIterator {
        defer { value += interval }
        return value < last ? value : nil
    }
})

for element in anySequence {
    print(element)
}

/*
prints:
0
2
4
6
8
*/

---

#4. Using CountableRange filter(_:) method

let first = 0
let last = 10
let interval = 2

let range = first ..< last
let lazyCollection = range.lazy.filter({ $0 % interval == 0 })

for element in lazyCollection {
    print(element)
}

/*
prints:
0
2
4
6
8
*/

---

#5. Using CountableRange flatMap(_:) method

let first = 0
let last = 10
let interval = 2

let range = first ..< last
let lazyCollection = range.lazy.compactMap({ $0 % interval == 0 ? $0 : nil })

for element in lazyCollection {
    print(element)
}

/*
prints:
0
2
4
6
8
*/