How do I check if an array of tuples contains a particular one in Swift?

Question

Consider the following Swift code.

var a = [(1, 1)]

if contains(a, (1, 2)) {
    println(\"Yes\")
}

All I need is to check if a

Answer 1

While tuples aren’t Equatable, you do not need to go so far as writing your own version of contains, since there is a version of contains that takes a matching predicate:

if contains(a, { $0.0 == 1 && $0.1 == 2 }) {
     // a contained (1,2)
}

While you can’t extend tuples to be equatable, you can write a version of == for tuples, which would make the above code simpler:

func ==(lhs: (T,U), rhs: (T,U)) -> Bool {
    return lhs.0 == rhs.0 && lhs.1 == rhs.1
}

contains(a) { $0 == (1,2) } // returns true

It’d be nice to be able to write a version of contains for tuples, but alas, I don’t think the placeholder syntax supports it:

EDIT: as of Swift 1.2, this does now compile as you can use tuples in placeholder constraints

func contains
  
  (seq: S, x: (T,U)) -> Bool {
    return contains(seq) { $0.0 == x.0 && $0.1 == x.1 }
}

let a = [(1,1), (1,2)]

if contains(a, (1,2)) {
    println("Yes")
}