Determine if a Range contains a value

range, swift

Solution

You can do it with the `~=` operator:

let point = (1, -1)
switch point {
case let (x, y) where (0..5) ~= x:
   println("(\(x), \(y)) has an x val between 0 and 5.")
default:
   println("This point has an x val outside 0 and 5.")
}

You can also do it directly in a switch:

let point = (1, -1)
let (x, y) = point
switch x {
case 0..5:
    println("yes")
default:
    println("no")
}

`~=` is the pattern match operator used by case statements. See details in the docs.

Problem

I'm trying to figure out a way to determine if a value falls within a `Range` in Swift. Basically what I'm trying to do is adapt one of the switch statement examples to do something like this: ``` let point = (1, -1) switch point { case let (x, y) where (0..5).contains(x): println("(\(x), \(y)) has an x val between 0 and 5.") default: println("This point has an x val outside 0 and 5.") } ``` As far as I can tell, there isn't any built in way to do what my imaginary `.contains` method above does. So I tried to extend the `Range` class. I ended up running into issues with generics though. I can't extend `Range<Int>` so I had to try to extend `Range` itself. The closest I got was this but it doesn't work since `>=` and `<=` aren't defined for `ForwardIndex` ``` extension Range { func contains(val:ForwardIndex) -> Bool { return val >= self.startIndex && val <= self.endIndex } } ``` How would I go about adding a `.contains` method to `Range`? Or is there a better way to determine whether a value falls within a range? Edit2: This seems to work to extend `Range` ``` extension Range { func contains(val:T) -> Bool { for x in self { if(x == val) { return true } } return false } } var a = 0..5 a.contains(3) // true a.contains(6) // false a.contains(-5) // false ``` I am very interested in the ~= operator mentioned below though; looking into that now.

Original source