performance_filter.swift

// Swift
let colds = fahrenheit.filter { (degreesFahrenheit) -> Bool in
    return degreesFahrenheit <= 68.0
}

// For-in loop
var colds = [Double]()     
for degreesFahrenheit in fahrenheit {
    if degreesFahrenheit <= 68.0 {
        colds.append(degreesFahrenheit)
    }
}