I'm new to programming. I was trying to understand how indices work in swift. This is the following code from swift documents. converted into function.

func ind(){
    var c = [10, 20, 30, 40, 50] //index = [0:5]
    var i = c.startIndex //i = [0]
    while i != c.endIndex { // i!= [5] , while i not equal to [5]
    c[i] /= 5
    i = c.index(after: i)
}
    print(c) // [2,4,6,8,10]
}

the code line i = c.index(after: i) doesn't seems to make sense to me. "after" means the character of string after the string.index, but because we initialized the 'i' to be zero(0) the output should stay [4 and onwards]. secondly, if i replace the i let's say with integer 2. the loop keeps repeating itself. why? Thank you in advance for your time

CodePudding user response：

after means the next element on your list in this context. An index is more general and is not limited to String. In addition, an index can have different types depending on the structure that you are manipulating.

For instance:

var c1 = [10, 20, 30, 40, 50] //
var i1 = c1.startIndex
// Print: Int
print(type(of: i1))

var c2 = "Hello" //
var i2 = c2.startIndex
// Print: Index
print(type(of: i2))

You can even create your own index for a specific type, as long as you provide a way to compute the next index.

Thus, in your code for this particular example, the index is of type Int. If you change the value of i to be the constant 2, you can never equal the value of the end index (which is 5 here). Then, your loop will never end.