Generic uniq function in Swift

uniq.swift

// uniq func for Swift 1.2

func uniq<C: ExtensibleCollectionType where C.Generator.Element: Hashable>(collection: C) -> C {
    var seen:Set<C.Generator.Element> = Set()
    
    return reduce(collection, C()) { result, item in
        if seen.contains(item) {
            return result
        }
        
        seen.insert(item)
        return result + [item]
    }
}

uniq([1, 2, 2, 2, 3, 4, 4]) // > [1, 2, 3, 4]
uniq("aaabccc") // > "abc"

uniq_superceded.swift

// uniq func for Swift 1.1

func uniq<C: ExtensibleCollectionType where C.Generator.Element: Hashable>(collection: C) -> C {
    var seen: [C.Generator.Element: Void] = [:]
    
    return reduce(collection, C()) { result, item in
        if seen[item] != nil {
            return result
        }
        
        seen[item] = ()
        return result + [item]
    }
}

uniq([1, 2, 2, 2, 3, 4, 4]) // > [1, 2, 3, 4]
uniq("aaabccc") // > "abc"

I updated it for Xcode 7 beta 4, and wrote about it here: http://kelan.io/2015/collection-extensions-in-swift-uniq-and-tapdescription/