Swift closure playground

// Playground - noun: a place where people can play

let list: Int[] = [1, 2, 3, 4, 5, 6]

func sum (a: Int, b: Int) -> Int {
    return a + b;
}

// function
list.reduce(0, combine: sum)


let closureSum = {
    (a: Int, b: Int) -> Int in
        a + b // note: return statement optional!
    }

// named closure (essentially a function)
list.reduce(0, combine: closureSum)

// closure
list.reduce(0, combine: {
    (a: Int, b: Int) -> Int in
    a + b
    })

// closure with inferred types
list.reduce(0, combine: {
    (a, b) in a + b
    })

// closure with numbered arguments
list.reduce(0, combine: {
    $0 + $1
})

// closure with argument label omitted
list.reduce(0, {
    $0 + $1
    })

// closure as last argument
list.reduce(0) { $0 + $1 }

// operator
list.reduce(0, combine: +)