Swift closure - Shorthand Closure

SwiftClosure-ShorthandClosure.swift

// Declare a variable to hold a closure
var add: (Int, Int) -> Int

/** SHORTHAND SYNTAX **/

// Not need return keyword when only have single return statement
add = {(a: Int, b: Int) -> Int in
    a + b
}
add(1, 1)

// Remove return type and parameters type
// Because we already declare: var add: (Int, Int) -> Int
add = {(a, b) in
    a + b
}

add(9, 2)

// Remove parameters, Swift will refer parameters by number, start from 0:
add = {
    $0 + $1
}

add(99, 1)