No output in Swift Playground - ios

Question

I am trying to put fibonacci number in an array and wanted to see the array output in playground console but for some reason I do not see any ouput. Can someone plz help in making me understand the mistake that I am cdoing in my program ?
import UIKit
class FibonacciSequence {
let includesZero: Bool
let values: [Int]
init(maxNumber: Int, includesZero: Bool) {
self.includesZero = includesZero
values = [0]
var counter: Int
if (includesZero == true) { counter = 0 }
else { counter = 1 }
for counter <= maxNumber; {
if ( counter == 0 ) {
values.append(0)
counter = 1
}
else {
counter = counter + counter
values.append(counter)
}
}
println(values)
}
println(values)
return values
}
let fibanocciSequence = FibonacciSequence(maxNumber:123, includesZero: true)

Answer 1

#ABakerSmith has given you a good rundown of the problems in the code as-is, but you also might want to consider, instead of a class that initializes an array member variable, writing a SequenceType that returns fibonacci numbers:
struct FibonacciSequence: SequenceType {
let maxNumber: Int
let includesZero: Bool
func generate() -> GeneratorOf<Int> {
var (i, j) = includesZero ? (0,1) : (1,1)
return GeneratorOf {
(i, j) = (j, i+j)
return (i < self.maxNumber) ? i : nil
}
}
}
let seq = FibonacciSequence(maxNumber: 20, includesZero: false)
// no arrays were harmed in the generation of this for loop
for num in seq {
println(num)
}
// if you want it in array form:
let array = Array(seq)
You could of course memoize the sequence if you want to improve performance on multiple generations.

Answer 2

Your problem is your code has errors in it; if there are errors in your code Playgrounds won't run it and you won't get any output.
On the line for counter <= maxNumber; you've got a semi-colon, but also, I'm pretty sure you can't declare a for loop like that, unless I'm missing something? You could use a while loop though.
Why are you trying to return values from your init method?
You've declared values as a constant but are then trying to change it using append.
Using this code and fixing the errors stated does not produce the Fibonacci sequence, instead it produces: [0, 0, 2, 4, 8, 16, 32, 64, 128]
Try this code:
class FibonacciSequence {
let values: [Int]
init(maxNumber: Int, includesZero: Bool) {
var tempValues = includesZero ? [0] : [1]
var current = 1
do {
tempValues.append(current)
let nMinus2 = tempValues[tempValues.count - 2]
let nMinus1 = tempValues[tempValues.count - 1]
current = nMinus2 + nMinus1
} while current <= maxNumber
self.values = tempValues
}
}
Then create an instance:
let fibanocciSequence = FibonacciSequence(maxNumber:123, includesZero: true)
println(fibanocciSequence.values) // [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89]
Hope that helps!