Varying Swift syntax for map function

SwiftMapExercise.swift

// Most verbose: No compiler assumptions are made, the closure to map
// receives a transforming function explicitly casted as (val: Int) -> Int
// Transforms an array of Int and multiplies each value by 10 
arrValues.map({ (val: Int) -> Int in 
               return val * 10 
              })

// Compiler assumes return type for closure, no need to explicitly indicate
arrValues.map({ (val: Int) in 
               return val * 10 
              })

// Compiler assumes data type for closure parameter (of type Int)
arrValues.map({ (val) in 
               return val * 10 
              })

// Compiler assumes last value in closure is returned and is of type Int
arrValues.map({ (val) in 
               val * 10 
              })

// Compiler assumes the first (and only, for this case) parameter in closure 
// is of type Int, the last value in closure is returned and is of type Int,
// and assumes the return type of the clusre is also of type Int (from the data
// type of the value operated by `$0 * 10` (Int)
arrValues.map({ $0 * 10 })

// Assumes same as above but since the last parameter for map is a closure
// (ie. a trailing closure), there is no need to indicate parenthesis and
// brackets will suffice
arrValues.map{ $0 * 10 }