C# - 演算子のオーバーロード(等価演算子のオーバーロード、Equalsメソッド)

初めてのC# 第2版
Jesse Liberty (著) Brian MacDonald (著)
日向俊二 (訳)
原書: Learning C# 2005

開発環境

• Microsoft Windows 8 Pro 64bit 日本語 (OS)
• Microsoft Visual Studio Express 2012 for Windows Desktop (IDE)
• プログラミング言語: C#

『初めてのC# 第2版』(Jesse Liberty+Brian MacDonald著、日向俊二訳、オライリー・ジャパン、2006年、ISBN978-487311-294-7)の 第12章(演算子のオーバーロード)12.6(練習問題)練習12-2を解いてみる。

その他参考書籍

• プログラミングC# 第6版

練習12-2.

コード

using System;

class Invoice
{
    private string vendor;
    private double amount;
    public string Vendor
    {
        get { return vendor; }
        set { vendor = value; }
    }
    public double Amount
    {
        get { return amount; }
        set { amount = value; }
    }
    public Invoice(string vendor, double amount)
    {
        this.vendor = vendor;
        this.amount = amount;
    }
    public static Invoice operator +(Invoice lhs, Invoice rhs)
    {
        if (lhs.vendor == rhs.vendor)
        {
            return new Invoice(lhs.vendor, lhs.amount + rhs.amount);
        }
        return new Invoice("", 0);
    }
    public static bool operator ==(Invoice lhs, Invoice rhs)
    {
        if (lhs.vendor == rhs.vendor && lhs.amount == rhs.amount)
        {
            return true;
        }
        return false;
    }
    public static bool operator !=(Invoice lhs, Invoice rhs)
    {
        return !(lhs == rhs);
    }
    public override bool Equals(object obj)
    {
        if (!(obj is Invoice))
        {
            return false;
        }
        return this == (Invoice)obj;
    }
    public override int GetHashCode()
    {
        return base.GetHashCode();
    }
}

class Tester
{
    public void Run()
    {
        Invoice yamato = new Invoice("yamato1", 1.2);
        Invoice yamato11 = new Invoice("yamato1", 1.2);
        Invoice yamato12 = new Invoice("yamato1", 2.10);
        Invoice yamato21 = new Invoice("yamato2", 1.2);
        Invoice yamato22 = new Invoice("yamato2", 2.1);
        Invoice[] invoices = {yamato11, yamato12, yamato21, yamato22 };
        Console.WriteLine("vendor:{0} amount:{1}と同じかどうか？", yamato.Vendor, yamato.Amount);
        foreach (Invoice invoice in invoices)
        {
            string result = yamato == invoice ? "同じ" : "異なる";
            Console.WriteLine("vendor:{0} amount:{1} {2}", invoice.Vendor, invoice.Amount, result);
        }
    }
    static void Main()
    {
        Tester t = new Tester();
        t.Run();
    }
}

入出力結果(Console Window)

vendor:yamato1 amount:1.2と同じかどうか？
vendor:yamato1 amount:1.2 同じ
vendor:yamato1 amount:2.1 異なる
vendor:yamato2 amount:1.2 異なる
vendor:yamato2 amount:2.1 異なる
続行するには何かキーを押してください . . .

ちなみにJavaScriptの場合。

コード(TextWrangler)

// JavaScriptでは演算子のオーバーロードはできない(？)のでとりあえずequalメソッドを定義してみることに
var result = "";
var Invoice = function(vendor, amount){
  var vendor = vendor;
  var amount = amount;
  this.get_vendor = function(){
    return vendor;
  };
  this.set_vendor = function(value){
    vendor = value;
  };
  this.get_amount = function(){
    return amount;
  };
  this.set_amount = function(value){
    amount = value;
  };
  this.add = function(other){
    if(vendor === other.get_vendor()){
      return new Invoice(vendor, amount + other.get_amount());
    } else {
      return new Invoice("", 0);
    }
  };
  this.equals = function(other){
    if(typeof(this) != typeof(other))return false;
    if(vendor === other.get_vendor() && 
      amount === other.get_amount()){
      return true;
    }
    return false;
  };
};
var yamato = new Invoice("yamato1", 1.2);
var yamato11 = new Invoice("yamato1", 1.2);
var yamato12 = new Invoice("yamato1", 2.1);
var yamato21 = new Invoice("yamato2", 1.2);
var yamato22 = new Invoice("yamato2", 2.1);
var invoices = [yamato11, yamato12, yamato21, yamato22];
result += "vneodr:" + yamato.get_vendor() + " amount:" + yamato.get_amount() + "と同じか？\n";
for(var i = 0; i  < invoices.length; i++){
  result += "name:" + invoices[i].get_vendor() + " amount:" + 
    invoices[i].get_amount() + " ";
  result += yamato.equals(invoices[i]) ? "同じ" : "異なる";
  result += "。\n";
}
$('#pre0').text(result);

pythonの場合。

sample.py

コード(TextWrangler)

#!/usr/bin/env python3.3
# -*- coding: utf-8 -*-

class Invoice:
    def __init__(self, vendor, amount):
        self._vendor = vendor
        self._amount = amount
    
    def get_vendor(self):
        return self._vendor
    
    def set_vendor(self, value):
        self._vendor = value
    
    def get_amount(self):
        return self._amount
    
    def set_amount(self, value):
        self._amount = amount
    
    def __add__(self, other):
        if self._vendor == other.get_vendor():
            return Invoice(self._vendor, self._amount + other.get_amount())
        else:
            return Invoice("", 0)
    
    def __radd__(self, other):
        if self._vendor == other.get_vendor():
            return Invoice(self._vendor, other.get_amount() + self._amount)
        else:
            return Invoice("", 0)
    def __eq__(self, other):
        if self._vendor == other.get_vendor() and self._amount == other.get_amount():
            return True
        return False
    
    def __ne__(self, other):
        return not (self == other)
 
yamato = Invoice("yamato1", 1.2)   
yamato11 = Invoice("yamato1", 1.2)
yamato12 = Invoice("yamato1", 2.1)
yamato21 = Invoice("yamato2", 1.2)
yamato22 = Invoice("yamato2", 2.1)

invoices = [yamato11, yamato12, yamato21, yamato22]

print("vendor:{0} amount:{1}と同じかどうか？".format(yamato.get_vendor(),
  yamato.get_amount()))

for invoice in invoices:
    result = "同じ" if yamato == invoice else "異なる"
    print("vendor:{0} amount:{1} {2}".format(invoice.get_vendor(),
      invoice.get_amount(), result))

入出力結果(Terminal)

$ ./sample.py
vendor:yamato1 amount:1.2と同じかどうか？
vendor:yamato1 amount:1.2 同じ
vendor:yamato1 amount:2.1 異なる
vendor:yamato2 amount:1.2 異なる
vendor:yamato2 amount:2.1 異なる
$