Swift Dictionary Initialization of Custom Type Gives: '>' Is Not a Postfix Unary Operator Error

Swift Dictionary Initialization of custom type gives: '' is not a postfix unary operator error

While I can't tell you why the swift compiler emits this error, you can make it compile like this:

struct Prims {
    var msSet = Dictionary<Vertex<Int>, Double>()
}

or like this:

struct Prims {
    typealias V = Vertex<Int>
    var msSet = [V : Double]()
}

Why can't I use the short Array constructor syntax when creating an Array of a nested Struct?

It's just a hole in the language. After all, the [Type] syntax is just syntactic sugar; as you rightly say, if you use the real syntax with Array<Type>, or use [Type] but not as a constructor, there's no problem. You can also work around it with type alias:

struct Struct1 {
    struct Struct2 {
        var name: String?
    }
}

typealias Struct2 = Struct1.Struct2

var struct2Array = [Struct2]()

How to calculate percentage using % as a postfix unary operator in Swift 3 and still be able to use % for modulo?

Just move

var percentage = 25%

under

postfix func % (percentage: Int) -> Double {
    return (Double(percentage) / 100)
}

Like so

postfix operator %

postfix func % (percentage: Int) -> Double {
    return (Double(percentage) / 100)
}

var percentage = 25%

Reason: your code would work in an app, but not in a playground, because a playground interprets the code from top to bottom. It doesn't see the postfix func declaration located below var percentage, so at the point of var percentage it gives you an error, because it doesn't yet know what to do with it.

Weird escaping function behavior after updating to Swift 3

Looks like a bug to me. For some reason, the compiler doesn't like the syntax:

private var functionHandlers = [(@escaping () -> Int) -> ()]()

but it does like:

private var functionHandlers : [(@escaping () -> Int) -> ()] = []

It's the same symptom, but I'm unsure it's the same cause as the compiler rejecting the [TypeA.TypeB]() syntax with nested types. Although like that problem, another way of solving it is by using a typealias:

typealias F = (@escaping () -> Int) -> ()

private var functionHandlers = [F]()

You can then implement doRegister() as you correctly tried to implement it as:

func doRegister() {
    functionHandlers.append { (f: @escaping () -> Int) in
        myFunction = f
    }
}

Although you should certainly file a bug report over [(@escaping () -> Int) -> ()]() not compiling.

unary operator expected error in Bash if condition

If you know you're always going to use Bash, it's much easier to always use the double bracket conditional compound command [[ ... ]], instead of the POSIX-compatible single bracket version [ ... ]. Inside a [[ ... ]] compound, word-splitting and pathname expansion are not applied to words, so you can rely on

if [[ $aug1 == "and" ]];

to compare the value of $aug1 with the string and.

If you use [ ... ], you always need to remember to double quote variables like this:

if [ "$aug1" = "and" ];

If you don't quote the variable expansion and the variable is undefined or empty, it vanishes from the scene of the crime, leaving only

if [ = "and" ];

which is not a valid syntax. (It would also fail with a different error message if $aug1 included white space or shell metacharacters.)

The modern [[ operator has lots of other nice features, including regular expression matching.

jQuery: Return javascript array from Ajax-callback

You should return just the object, not a string of JavaScript which assigns the object to a name. That's NOT a JSON response.

Your code which uses the object should be in the success handler of the ajax call, not separate code somewhere else.

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