Hello,

this is basic language question about closure sorting of array:

```
let compareAscending = { (i: Int, j: Int) -> Bool in
return i < j
}
var numbers = [42, 9, 12, -17]
numbers.sort(by: compareAscending)
```

I don’t get how the underlying sorting mechanism works.

I get it compares two numbers and returns a bool if first number > second number, but how does it sort the entire array then?

What is the sequence of operations?