Which Way Am I Sorting?

I always got confused as to what’s the end result my sort. I wasn’t sure if it would end up being ascending or descending. The ultimate trick is to not think of up vs down. Instead think of increasing/decreasing from left to right.
We perceive arrays as horizontal beings. Hence left and right make more sense vs up and down

let nums = [1,4,2,3]
let sorted_nums = arr.sorted(by: {
    $0 < $1 // left is smaller  [1,2,3,4] i.e. ascending
})

If you see $0 < $1 then left side is smaller than the next item. i.e. it’s ascending.

let nums = [1,4,2,3]
let sorted_nums = arr.sorted(by: {
    $0 > $1  // left is bigger [4,3,2,1] i.e. descending
})

If you see $0 > $1 then right side is smaller than the next item. i.e. it’s descending. Similarly writing array.sorted(by: <) is identical.

Alternate way:

• array.sorted(by: <) will make it decreasing.
• array.sorted(by: >) will make it increasing.

And if I don’t pass a block?

It will make the array increasing. Increasing is more natural as that’s how we’d list numbers from 1…n and we almost never list numbers n…1.

let nums = [1,4,2,3]
print(nums.sorted()) // [1,2,3,4]

$0 vs $1

Never place the $1 on the left side when sorting. $0 is the first number, $1 is the second number in the comparison. If you switch them then the order will get reversed.