y.swift

gistfile1.txt

// Y-combinator in Swift.

func Y<y,⒴>(𝖸:((y)->⒴)->((y)->⒴))->((y)->⒴){
    var Ｙ:((y)->⒴)!;Ｙ=𝖸{Ｙ($0)};return Ｙ
}

// Couldn't find a way to avoid such explicitness.
// If types are defined in the inner function, compiler cannot infer type of 'f'.
let factorial = Y {(f:((Int)->Int)) -> ((Int)->Int) in
    return {n in
        return n == 0 ? 1 : n*f(n-1)
    }
}

for i in 0...6 {
    println("factorial(\(i)) = \(factorial(i))");
}