Swap functions

main.swift

// Copyright (c) 2014 Shintaro Kaneko
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

/**
    Exchange the values of `x` and `y`

    :param: x The pointer of the value
    :param: y The pointer of the value
 */
func swapByPointer<T>(x: UnsafeMutablePointer<T>, y: UnsafeMutablePointer<T>) {
    let z: T = x.memory
    x.memory = y.memory
    y.memory = z
}

/**
    Exchange the values of `x` and `y`

    :param: x The pointer of the value
    :param: y The pointer of the value
*/
func swapByInout<T>(inout x: T, inout y: T) {
    let z: T = x
    x = y
    y = z
}

// ====================

var a: Int = 10
var b: Int = 20

// a = 10, b = 20
println("a = \(a), b = \(b)")

// Swap `a` for `b`
swapByInout(&a, &b)

// a = 20, b = 10
println("a = \(a), b = \(b)")

// Swap
swapByPointer(&a, &b)

// a = 10, b = 20
println("a = \(a), b = \(b)")

// ====================

// Use UnsafeMutablePointer<T>
typealias IntPointer = UnsafeMutablePointer<Int>

// Assign
var a_ptr = IntPointer.alloc(1)
var b_ptr = IntPointer.alloc(1)

a_ptr.memory = a
b_ptr.memory = b

// a_ptr.memory = 10, b_ptr.memory = 20
println("a_ptr.memory = \(a_ptr.memory), b_ptr.memory = \(b_ptr.memory)")

// Swap
swapByPointer(a_ptr, b_ptr)

// a_ptr.memory = 20, b_ptr.memory = 10
println("a_ptr.memory = \(a_ptr.memory), b_ptr.memory = \(b_ptr.memory)")

// Destroy
a_ptr.dealloc(1)
b_ptr.dealloc(1)