min and max are defined in Swift:
func max<T : Comparable>(x: T, y: T, rest: T...) -> T
func min<T : Comparable>(x: T, y: T, rest: T...) -> T
and used like so:
let min = min(1, 2)
let max = max(1, 2)
See this great writeup on documented & undocumented built-in functions in Swift.