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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>page_1001</title> <link rel="stylesheet" href="reset.css" type="text/css" media="all"> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> </head> <body> <table summary="top nav" border="0" width="100%"> <tr> <td align="left" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_1000.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_1001</strong></td> <td align="right" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_1002.html">next page ></a></td> </tr> <tr> <td align="left" colspan="3" style="background: #ffffff; padding: 20px;"> <table border="0" width="100%" cellpadding="0"><tr><td align="center"> <table border="0" cellpadding="2" cellspacing="0" width="100%"><tr><td align="left"></td> <td align="right"></td> </tr></table></td></tr><tr><td align="left"><p></p><table border="0" cellspacing="0" cellpadding="0" width="100%"><tr><td align="right"><font face="Times New Roman, Times, Serif" size="2" color="#FF0000">Page 1001</font></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">In summary, the default operations of assignment and initialization may be dangerous when class objects point to dynamic data on the free store. Member-by-member assignment and initialization cause only pointers to be copied, not the pointed-to data. If a class allocates and deallocates data on the free store, it almost certainly needs the following suite of member functions to ensure deep copying of dynamic data:</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">class聽SomeClass<br />{<br />public:<br />聽聽聽聽聽聽.<br />聽聽聽聽聽聽.<br />聽聽聽聽聽聽.<br />聽聽聽聽void聽CopyFrom(聽SomeClass聽anotherObject聽);<br />聽聽聽聽聽聽聽聽//A聽deep聽copy聽operation<br /><br />聽聽聽聽SomeClass(聽聽);<br />聽聽聽聽聽聽聽聽//聽Constructor,聽to聽create聽data聽on聽the聽free聽store<br /><br />聽聽聽聽SomeClass(聽const聽SomeClass&聽anotherObject聽);<br />聽聽聽聽聽聽聽聽//聽Copy-constructor,聽for聽deep聽copying聽in聽initializations<br /><br />聽聽聽聽~SomeClass();<br />聽聽聽聽聽聽聽聽//聽Destructor,聽to聽clean聽up聽the聽free聽store<br />private:<br />聽聽聽聽.<br />聽聽聽聽.<br />聽聽聽聽.<br />};</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">At the beginning of this chapter, we said that pointers are used for two reasons: to make a program more efficienteither in speed or in memory usageand to create complex data structures called linked structures. We give examples of the use of pointers to make a program more efficient in the case studies in this chapter. Linked structures are covered in Chapter 18.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="17"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">Problem-Solving Case Study Personnel Records</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3"><img src="648ee8597c617eb2c63f518749717475.gif" border="0" alt="1001-01.gif" width="118" height="142" /></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">Problem: We have a file of personnel records, and there is a great deal of data associated with each person. The task is to read in these records, sort them alphabetically by last name, and print out the sorted records.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">Input: A file of personnel records (</font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">masterFile</font><font face="Times New Roman, Times, Serif" size="3">), where each record corresponds to the data type </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">PersonnelData</font><font face="Times New Roman, Times, Serif" size="3"> in the declarations below.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table></td></tr></table><p><font size="0"></font></p>聽 </td> </tr> <tr> <td align="left" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_1000.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_1001</strong></td> <td align="right" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_1002.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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