gistfile1.swift

struct IterateVars<T> {
    let f: T -> T
    
    func go(inout x: T) -> IterateVars {
        x = f(x)
        return self
    }
}

var a = 2.0;
var b = 3.0;
var c = 4.0;
var d = 5.0;

IterateVars{ $0 * 2 }.go(&a).go(&b).go(&c).go(&d)
IterateVars{ $0 + 10 }.go(&a).go(&b).go(&c).go(&d)