📄 page_463.html
字号:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>page_463</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_462.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_463</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_464.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 463</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">Switch statement is that </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">grade</font><font face="Times New Roman, Times, Serif" size="3"> is definitely one of A, B, C, D, or F, it would be wise to include a default label to account for an invalid grade:</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">switch聽(grade)<br />{<br />聽聽聽聽case聽A聽:<br />聽聽聽聽case聽B聽:聽cout聽<<聽Good聽Work;<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break;<br />聽聽聽聽case聽C聽:聽cout聽<<聽Average聽Work;<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break;<br />聽聽聽聽case聽D聽:<br />聽聽聽聽case聽F聽:聽cout聽<<聽Poor聽Work;<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numberInTrouble++;<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break;<br />聽聽聽聽default聽聽:聽cout聽<<聽grade聽<<聽聽is聽not聽a聽legal聽letter聽grade.;<br />聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽break;<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">A Switch statement with a </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">break</font><font face="Times New Roman, Times, Serif" size="3"> statement after each case alternative behaves exactly like an If-Then-Else-If control structure. For example, our Switch statement is equivalent to the following code:</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">if聽(grade聽==聽A聽||聽grade聽==聽B)<br />聽聽聽聽cout聽<<聽Good聽Work;<br />else聽if聽(grade聽==聽C)<br />聽聽聽聽cout聽<<聽Average聽Work;<br />else聽if聽(grade聽==聽D聽||聽grade聽==聽F)<br />{<br />聽聽聽聽cout聽<<聽Poor聽Work;<br />聽聽聽聽numberInTrouble++;<br />}<br />else<br />聽聽聽聽cout聽<<聽grade聽<<聽聽is聽not聽a聽legal聽letter聽grade.;</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">Is either of these two versions better than the other? There is no absolute answer to this question. For this particular example, our opinion is that the Switch statement is easier to understand because of its two-dimensional, table-like form. But some may find the If-Then-Else-If version easier to read. When implementing a multi-way branching structure, our advice is to write down both a Switch and an If-Then-Else-If and then compare them for readability. Keep in mind that C++ provides the Switch statement as a matter of convenience. Don't feel obligated to use a Switch statement for every multiway branch.</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">Finally, we said we would look at what happens if you omit the </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">break</font><font face="Times New Roman, Times, Serif" size="3"> statements inside a Switch statement. Let's rewrite our letter grade example without the </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">break</font><font face="Times New Roman, Times, Serif" size="3"> statements:</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_462.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_463</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_464.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -