Swift bug when formatting CGFloats

CGFloatFormattingBug.swift

import Cocoa

// Doesn't work for CGFloats
let a: CGFloat = 1.0
let b: CGFloat = 2.0
String(format: "%f %f", a, b)   // "0.000000 0.000000"

// Works for Floats
let c: Float = 1.0
let d: Float = 2.0
String(format: "%f %f", c, d)   // "1.000000 2.000000"

// Works for Doubles
let e: Double = 1.0
let f: Double = 2.0
String(format: "%f %f", e, f)   // "1.000000 2.000000"

Swift's String is extended in Foundation to include most of NSString's initializers—you can see all of them by command-clicking on an import Foundation statement or on the SwiftDoc.org String page marked with [Foundation].