定义一个名为rectangle 的矩形类，其属性数据为矩形左上角和右上角的点的坐标能计算矩形的面积

======================================================================== CONSOLE APPLICATION : 1 ======================================================================== AppWizard has created this 1 application for you. This file contains a summary of what you will find in each of the files that make up your 1 application. 1.dsp This file (the project file) contains information at the project level and is used to build a single project or subproject. Other users can share the project (.dsp) file, but they should export the makefiles locally. 1.cpp This is the main application source file. ///////////////////////////////////////////////////////////////////////////// Other standard files: StdAfx.h, StdAfx.cpp These files are used to build a precompiled header (PCH) file named 1.pch and a precompiled types file named StdAfx.obj. ///////////////////////////////////////////////////////////////////////////// Other notes: AppWizard uses "TODO:" to indicate parts of the source code you should add to or customize. /////////////////////////////////////////////////////////////////////////////