How does the Swift string more than operator work

Question

I was reading the documentation on the Swift programming language, when I came across the following code snippet:

let names = ["Chris", "Alex", "Ewa", "Barry", "Daniella"]

func backwards(s1: String, _ s2: String) -> Bool {
   return s1 > s2
}

names.sort(backwards) // ["Ewa", "Daniella", "Chris", "Barry", "Alex"]

What I don't seem to be able to find, is how the > operator works in this context, I thought it would do something like count the amount of characters and then return a boolean based on that, but with that logic the following snippet should return false:

"CD" > "ABC" // true

Could someone please explain what is going on here?

what is your current knowledge / understanding of string comparison? — Wain, Jul 12 '16 at 13:52
@Wain I've only ever used basic `==`, `===`, `!=` in other languages, so seeing a more than / less than being used is quite new — Paradoxis, Jul 12 '16 at 13:53

score 1 · Answer 1 · edited May 23 '17 at 12:14

1

Swift does lexicographical string comparison. This has been asked before you can check it out here

edited May 23 '17 at 12:14

Community

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answered Jul 12 '16 at 13:58

Dickson Leonard

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score 1 · Accepted Answer · answered Jul 12 '16 at 14:00

1

I believe javascript uses exactly the same string comparison approach, and the same syntax. In javascript you could also use localeCompare(). And in swift you could alternatively use localizedCompare(_:) (or one of the other string comparison functions). They're all different ways, and with different options, to alphabetically compare strings.

answered Jul 12 '16 at 14:00

Wain

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Addition, Swift 2.2.30: from the [String.swift source code](https://github.com/apple/swift/blob/master/stdlib/public/core/String.swift) we can see that e.g. the `<` operator for `String` is defined as `lhs._compareString(rhs) < 0` (which use `_swift_stdlib_unicode_compare_utf8_utf8`, itself), which we can track via https://github.com/apple/swift/blob/master/stdlib/public/stubs/UnicodeNormalization.cpp to `ucol_strcollIter` (see `MakeRootCollator` for collator) from [ICU lib](http://icu-project.org/apiref/icu4c/ucol_8h.html); i.e., using [unicode collation](http://unicode.org/reports/tr10/). – dfrib Jul 12 '16 at 14:34

How does the Swift string more than operator work

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