generics - Swift - how to declare a method which receives a number in a range -

i want create function has number parameter should between 0..100 %

i thought best way enforce creating wrapper type using floatingpointtype protocol , getting compilation error

protocol 'floatingpointtype' can used generic constraint because has self or associated type requirements

struct percent {     init(val : floatingpointtype) {         // enforce value between 0..100     } }   func hideview(percent : percent) {   // percent 0..100 @ point .. work here } 

what correct way enforce condition @ compile time?

the easiest way define type holds double (or float or int) in required range:

struct p {     let val : double     init (val : double) {         // ...     } } 

but if want treat different floating point types have define generic class

struct percent<t : floatingpointtype> {     let val : t     init(val : t) {        self.val = val     } } 

to compare values need require equatable well:

struct percent<t : floatingpointtype t: equatable> {     let val : t     init(val : t) {         if val < t(0) {             self.val = t(0)         } else if val > t(100) {             self.val = t(100)         } else {             self.val = val         }     } } 

example:

let p = percent(val: 123.4) println(p.val) // 100.0 

note requires hideview() generic well:

func hideview<t>(percent : percent<t>) {     // percent.val has type `t` , in range     // t(0) ... t(100) }