Multiple optional bindings in Swift (i.e. the equivalent of if let (a, b, c) = (optA, optB, optC) { ... })

gistfile1.swift

// The DSL's implementation (i.e. just the applicative interface for Optionals + methods for creating tuples)
operator infix <*>  { associativity left }
@infix func <*><A, B>(lhs: (A -> B)?, rhs: A?) -> B? {
    switch lhs {
    case .None:
        return .None
    case let .Some(f):
        return rhs.map(f)
    }
}

operator infix => { associativity left }
@infix func =><A, B>(f: A -> B, x: A?) -> B? {
    return x.map(f)
}

func zip<A, B>(a: A)(b: B) -> (A, B) {
    return (a, b)
}

func zip<A, B, C>(a: A)(b: B)(c: C) -> (A, B, C) {
    return (a, b, c) // segfault - seems to a be a compiler bug in code-gen
}


// Example usage
var a: Int[]? = [5]
var s: String? = "5"
var f: Float? = 5.0

println("Before zip")
if let (av, sv, fv) = (zip => a <*> s <*> f) {
    println("\(av) and \(sv) and \(fv)")
}