A basic syntax question I'm having just starting out with the Swift programming language ... I wished @twostraws would have added a video on whitespace for the #100DaysOfSwitUI 😜

100DaysOfSwiftUI - Day 9 - Checkpoint 5 - Whitespace.swift

// ==============================================================================================
//   How can it be explained that Swift interprets whitespace and whitespace so differently?!?
// ----------------------------------------------------------------------------------------------
//   Must be some "a line break makes a chain of commands a sequence and therefore a line
//   break cannot be used in places where a semicolon would obviously not be allowed". But
//   I don't see it and some explanation would be much appreciated!
// ==============================================================================================

let luckyNumbers = [7, 4, 38, 21, 16, 15, 12, 33, 31, 49]

// ✅ This one does compile ...
for n in luckyNumbers .filter { !$0.isMultiple(of: 2) } .sorted { $0 <= $1 } .map { "\($0) is a lucky number"} {
    print(n)
}

// ✅ And this one does compile ...
for n in luckyNumbers
    .filter { !$0.isMultiple(of: 2) } .sorted { $0 <= $1 } .map { "\($0) is a lucky number"} {
    print(n)
}

// ✅ As well as this one ...
for n in luckyNumbers
    .filter { !$0.isMultiple(of: 2) } .sorted { $0 <= $1 } .map
    { "\($0) is a lucky number"} {
    print(n)
}

// ✅ Or this ...
for n in luckyNumbers .filter
    { !$0.isMultiple(of: 2) } .sorted { $0 <= $1 } .map { "\($0) is a lucky number"} {
    print(n)
}

// ✅ Even this compiles ...
for n in luckyNumbers .filter
    { !$0.isMultiple(of: 2) } .sorted
    { $0 <= $1 } .map
    { "\($0) is a lucky number"} {
    print(n)
}

// ❌ But neither this ...
for n in luckyNumbers
    .filter { !$0.isMultiple(of: 2) } .sorted { $0 <= $1 }
    .map { "\($0) is a lucky number"} {
    print(n)
}

// ❌ Nor this ..
for n in luckyNumbers .filter { !$0.isMultiple(of: 2) } .sorted { $0 <= $1 }
    .map { "\($0) is a lucky number"} {
    print(n)
}

// ❌ And regretably this (🏆 my preferd formatting in this case) does not compile either ...
for n in luckyNumbers
    .filter { !$0.isMultiple(of: 2) }
    .sorted { $0 <= $1 }
    .map { "\($0) is a lucky number"} {
    print(n)
}

// ----------------------------------------------------------------------------------------------
// Maybe not easy to spot and so if you haven't seen it yet: All of the examples above
// only differ in where the line breaks have been placed - nothing else has been changed.
// But for the following ones I actually changed the code itself to make it work despite
// the line breaks ... but this is not really what the problem described above is about.
// ----------------------------------------------------------------------------------------------

// ✅ Sure, this one (🏆 my prefered solution) works - but it's something completely different ...
luckyNumbers
    .filter { !$0.isMultiple(of: 2) }
    .sorted { $0 <= $1 }
    .map { "\($0) is a lucky number" }
    .forEach { print($0) }

// ✅ And yes, you get the formatting right avoiding trailing closures - which leads to bad formatting ...
for n in luckyNumbers
    .filter({ !$0.isMultiple(of: 2) })
    .sorted(by: { $0 <= $1 })
    .map( { "\($0) is a lucky number" } ) {
    print(n)
}