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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_1020</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_1019.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_1020</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_1021.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 1020</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">Figure 17-9 depicted exactly the same strategy of keeping a pointer within a class object and letting it point to a dynamic array on the free store.</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">Specification of the Class: In choosing public operations for the </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">DynArray</font><font face="Times New Roman, Times, Serif" size="3"> class, we will retain the three operations from the </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">IntArray</font><font face="Times New Roman, Times, Serif" size="3"> class: </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">ValueAt</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">Store</font><font face="Times New Roman, Times, Serif" size="3">, and a class constructor. The job of the constructor, when it receives a parameter </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">arrSize</font><font face="Times New Roman, Times, Serif" size="3">, will be to allocate a dynamic array of exactly </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">arrSize</font><font face="Times New Roman, Times, Serif" size="3"> elementsno more, and no less. Because </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">DynArray</font><font face="Times New Roman, Times, Serif" size="3"> class objects point to dynamic data on the free store, we also need a deep copy operation, a class copy-constructor, and a class destructor. Here is the specification of </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">DynArray</font><font face="Times New Roman, Times, Serif" size="3">, complete with preconditions and postconditions for the member functions.</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">//******************************************************************<br />//聽SPECIFICATION聽FILE聽(dynarray.h)<br />//聽This聽file聽gives聽the聽specification聽of聽an聽integer聽array聽class<br />//聽that聽allows:<br />//聽聽聽聽1.聽Run-time聽specification聽of聽array聽size<br />//聽聽聽聽2.聽Trapping聽of聽invalid聽array聽indices<br />//聽聽聽聽3.聽Aggregate聽copying聽of聽one聽array聽to聽another<br />//聽聽聽聽4.聽Aggregate聽array聽initialization聽(for聽parameter聽passage聽by<br />//聽聽聽聽聽聽聽value,聽function聽value聽return,聽and聽initialization聽in聽a<br />//聽聽聽聽聽聽聽declaration)<br />//******************************************************************<br /><br />class聽DynArray<br />{<br />public:<br />聽聽聽聽int聽ValueAt(聽/*聽in聽*/聽int聽i聽)聽const;<br />聽聽聽聽聽聽聽聽//聽Precondition:<br />聽聽聽聽聽聽聽聽//聽聽聽聽聽i聽is聽assigned<br />聽聽聽聽聽聽聽聽//聽Postcondition:<br />聽聽聽聽聽聽聽聽//聽聽聽聽聽IF聽i聽>=聽0聽&&聽i聽<聽declared聽size聽of聽array<br />聽聽聽聽聽聽聽聽//聽聽聽聽聽聽聽聽聽Function聽value聽==聽value聽of聽array聽element<br />聽聽聽聽聽聽聽聽//聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽at聽index聽i<br />聽聽聽聽聽聽聽聽//聽聽聽聽聽ELSE<br />聽聽聽聽聽聽聽聽//聽聽聽聽聽聽聽聽聽Program聽has聽halted聽with聽error聽message<br /><br />聽聽聽聽void聽Store(聽/*聽in聽*/聽int聽val,<br />聽聽聽聽聽聽聽聽聽聽聽聽/*聽in聽*/聽int聽i聽聽聽);<br />聽聽聽聽聽聽聽聽//聽Precondition:<br />聽聽聽聽聽聽聽聽//聽聽聽聽聽val聽and聽i聽are聽assigned<br />聽聽聽聽聽聽聽聽//聽Postcondition:<br />聽聽聽聽聽聽聽聽//聽聽聽聽聽IF聽i聽>=聽0聽&&聽i聽<聽declared聽size聽of聽array<br />聽聽聽聽聽聽聽聽//聽聽聽聽聽聽聽聽聽val聽is聽stored聽in聽array聽element聽i<br /></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_1019.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_1020</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_1021.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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