Proper swift 2.2 syntax with for loop

Question

I wrote the following code in swift(2.2):

for var i = 2; sqrt(Double(num)) >= Double(i); i += 1 {.....}

However, I keep getting a warning message which reads "c-style for statement is deprecated and will be removed in future version of swift".

So, what is the proper way of writing the same loop is "Swift style"? Casting the value of num as double gives me error with "Swift style". Any suggestions?

Thank you.

Luca Angeletti · Accepted Answer · 2016-05-18T10:29:26.037

2

You can refactor your deprecated C-style for loop using the for-in construct

for i in 2...Int(sqrt(Double(num))) { }

However if you really want to go essential try defining this operator to find the square root of an int rounded down to the closest int.

prefix operator √ {}
prefix func √ (number: Int) -> Int {
     return Int(sqrt(Double(number)))
}

Now you can write your for loop this way

for i in 2...(√num) { }

edited May 18 '16 at 10:29

answered May 18 '16 at 10:17

Luca Angeletti

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Thank you. This solved the problem. – Saman Ray May 18 '16 at 13:10

score 1 · Answer 2 · answered May 18 '16 at 01:50

1

The For loop in Swift 2.2 is re-designed for use in iterating over a sequence, such as ranges of numbers, items in an array, or characters in a string. The condition in your For loop is not easily converted into sequence or range, so it would be best to re-write it as a While loop.

answered May 18 '16 at 01:50

bbabin

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Great observation due to recent Swift 3.x updates.. – Alessandro Ornano May 18 '16 at 06:48
4

"The condition in your For loop is not easily converted into sequence or range" - The answer by @appzYourLife above says otherwise ;) – Nicolas Miari May 18 '16 at 10:26

Proper swift 2.2 syntax with for loop

2 Answers2