Error summing up the array values in Swift

Question

I am new to Swift. Trying this code in Playground and get the error (see description below) Can you, please, point me to the right direction - where to look for the solution? Thanks in advance.

func randomSet(num: Int, max: Int) -> Array<Double> {

    var randArray = Array<Double>()

    for index in 0...num {
        randArray[index] = Double(arc4random_uniform(max+1))
    }

ERROR: var sum = randArray.reduce(0) {$0 + $1}

    for index in 0...num {
        randArray[index] = randArray[index] / Double(sum) * Double(max)
    }

    return randArray
}

test = randomSet(10, 100)

On the line marked with word ERROR, I get this:

Execution was interrupted, reason: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)

Please edit the title of your post to be more descriptive of the problem. How can I correct this? will be absolutely meaningless when it turns up in a search result by a future user here. Your title should describe the problem or contain a descriptive question that has some relevance. Thanks. — Ken White
– Ken White, Commented Feb 4, 2015 at 18:48
Note that 0...num includes the range end, so that will give you an array with num+1 elements. You probably want to 0 ..< num instead. — Martin R
– Martin R, Commented Feb 4, 2015 at 18:58

mattt · Accepted Answer · 2015-02-04 18:54:26Z

1

The error is actually caused by attempting to append values in randArray using subscripting. You should use append instead:

for _ in 0...num {
    randArray.append(Double(arc4random_uniform(max+1)))
}

answered Feb 4, 2015 at 18:54

mattt

19.5k7 gold badges75 silver badges84 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

HamzaGhazouani · Accepted Answer · 2015-02-04 18:55:51Z

1

The bug is not from the function reduce, but in initialization of your array, you can't access to index before initialization. The code below fix the bug.

  for index in 0...num {
    randArray.append(Double(arc4random_uniform(max+1)))
  }

Hope that helps

answered Feb 4, 2015 at 18:55

HamzaGhazouani

6,6226 gold badges35 silver badges41 bronze badges

1 Comment

Denis Rasulev Over a year ago

Thank you, Hamza, that made even more clear! In other words, I have to populate my array with some values before I can use index. Got it.

Collectives™ on Stack Overflow

Error summing up the array values in Swift

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related