C# - 演算子のオーバーロード( Equals 演算子、等価演算子と非等価演算子)

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、ISBN978-487312-194-7)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 Invoice(string vendor, double amount)
    {
        this.vendor = vendor;
        this.amount = amount;
    }
    public string Vendor
    {
        get { return vendor; }
    }
    public double Amount
    {
        get { return 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 i1 = new Invoice("Invoice1", 5);
        Invoice i2 = new Invoice("Invoice1", 10);
        Invoice i3 = new Invoice("Invoice2", 5);
        Invoice i4 = new Invoice("Invoice2", 10);
        Invoice i5 = new Invoice("Invoice3", 5);
        Invoice i6 = new Invoice("Invoice3", 10);
        Invoice[] invoices = {i2, i3, i4, i5, i6 };
        foreach (Invoice invoice in invoices)
        {
            Invoice i = i1+invoice;
            Console.WriteLine("({0}, {1}) + ({2}, {3}) = ({4}, {5})",
                i1.Vendor, i1.Amount, invoice.Vendor, invoice.Amount, i.Vendor, i.Amount);
        }
    }
    static void Main()
    {
        Tester t = new Tester();
        t.Run();
    }
}

入出力結果(Console Window)

(Invoice1, 5) == (Invoice1, 10): False
(Invoice1, 5) == (Invoice2, 5): False
(Invoice1, 5) == (Invoice2, 10): False
(Invoice1, 5) == (Invoice1, 5): True
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(BBEdit)

var Invoice = function ( vendor, amount ) {
    var vendor = vendor,
        amount = amount;
    this.getVendor = function (  ) {
        return vendor;
    },
    this.getAmount = function( ) {
        return amount;
    };
},
    i1 = new Invoice("Invoice1", 5),
    i2 = new Invoice("Invoice1", 10),
    i3 = new Invoice("Invoice2", 5),
    i4 = new Invoice("Invoice2", 10),
    i5 = new Invoice("Invoice1", 5),
    invoices = [i2, i3, i4, i5],
    result = "",
    i, max, invoice;
Invoice.prototype.add = function( a ) {
    if (this.getVendor() === a.getVendor()) {
        return new Invoice(this.getVendor(), this.getAmount() + a.getAmount());
    }
    return new Invoice("", 0);
},
Invoice.prototype.isEqual = function (o) {
    if (((typeof o === typeof Invoice) && (o instanceof Invoice) )) {
        return false;
    }
    return (this.getVendor() === o.getVendor()) && 
        (this.getAmount() === o.getAmount());
};
for (i = 0, max = invoices.length; i < max; i += 1) {
    result += "(" + i1.getVendor() + ", " + i1.getAmount() + "), (" +
        invoices[i].getVendor() + ", " + invoices[i].getAmount() + "): " +
        invoices[i].isEqual(i1) + "\n";
}
$('#pre0').text(result);

pythonの場合。

コード(BBEdit)

sample.py

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

class Invoice:
    def __init__(self, vendor, amount):
        self._vendor = vendor
        self._amount = amount
    def getVendor(self):
        return self._vendor
    def getAmount(self):
        return self._amount
    def __add__(self, y):
        if self._vendor == y._vendor:
            return Invoice(self._vendor, self._amount + y._amount)
        return Invoice("", 0)
    def __radd__(self, x):
        if x._vendor == self._vendor:
            return Invoice(x._vendor, x._amount + self._amount)
        return Invoice("", 0)
    def __eq__(self, y):
        if self._vendor == y._vendor and self._amount == y._amount:
            return True
        return False
    def __ne__(self, y):
        return not self == y

i1 = Invoice("Invoice1", 5)
i2 = Invoice("Invoice1", 10)
i3 = Invoice("Invoice2", 5)
i4 = Invoice("Invoice2", 10)
i5 = Invoice("Invoice1", 5)
invoices = [i2, i3, i4, i5]
for x in invoices:
    invoice = i1 + x
    print("({0}, {1}) == ({2}, {3}): {4}".format(
        i1.getVendor(), i1.getAmount(), x.getVendor(), x.getAmount(),
        i1 == x))

入出力結果(Terminal)

$ ./sample.py
(Invoice1, 5) == (Invoice1, 10): False
(Invoice1, 5) == (Invoice2, 5): False
(Invoice1, 5) == (Invoice2, 10): False
(Invoice1, 5) == (Invoice1, 5): True
$