C# - 演算子のオーバーロード(キーワードoperator)

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12-1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12-1.

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);
    }
}

class Tester
{
    public void Run()
    {
        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 = { yamato12, yamato21, yamato22 };
        foreach (Invoice invoice in invoices)
        {
            Console.WriteLine("({0}) + ({1}) = ({2})",
                yamato11.Vendor + ":" + yamato11.Amount,
                invoice.Vendor + ":" + invoice.Amount,
                (yamato11 + invoice).Vendor + ":" + (yamato11 + invoice).Amount);
        }
    }
    static void Main()
    {
        Tester t = new Tester();
        t.Run();
    }
}

入出力結果(Console Window)

(yamato1:1.2) + (yamato1:2.1) = (yamato1:3.3)
(yamato1:1.2) + (yamato2:1.2) = (:0)
(yamato1:1.2) + (yamato2:2.1) = (:0)
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add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);
    }
  };
};
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 = [yamato12, yamato21, yamato22];
for(var i = 0; i  < invoices.length; i++){
  result += "(" + yamato11.get_vendor() + ":" + yamato11.get_amount() + ") + " +
    "(" + invoices[i].get_vendor() + ":" + invoices[i].get_amount() + ") = " +
    "(" + (yamato11.add(invoices[i])).get_vendor() + ":" + 
    (yamato11.add(invoices[i])).get_amount() + ")\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)
    
yamato11 = Invoice("yamato1", 1.2)
yamato12 = Invoice("yamato1", 2.1)
yamato21 = Invoice("yamato2", 1.2)
yamato22 = Invoice("yamato2", 2.1)

invoices = [yamato12, yamato21, yamato22]

for invoice in invoices:
    print("({0}:{1}) + ({2}:{3}) = ({4}:{5})".format(
      yamato11.get_vendor(), yamato11.get_amount(),
      invoice.get_vendor(), invoice.get_amount(),
      (yamato11 + invoice).get_vendor(), (yamato11 + invoice).get_amount()))

入出力結果(Terminal)

$ ./sample.py
(yamato1:1.2) + (yamato1:2.1) = (yamato1:3.3)
(yamato1:1.2) + (yamato2:1.2) = (:0)
(yamato1:1.2) + (yamato2:2.1) = (:0)
$