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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_473</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_472.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_473</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_474.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 473</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="Courier New, Courier, Mono New, Courier, Mono" size="2">num1Valid聽=聽TRUE;<br />num2Valid聽=聽TRUE;<br />loopCount聽=聽1;<br />while聽(num1Valid聽&&聽num2Valid聽&&聽loopCount聽<=聽10)<br />{<br />聽聽聽聽cin聽>>聽numl;<br />聽聽聽聽if聽(聽!cin聽||聽numl聽>=聽100)<br />聽聽聽聽聽聽聽聽num1Valid聽=聽FALSE;<br />聽聽聽聽else<br />聽聽聽聽{<br />聽聽聽聽聽聽聽聽cin聽>>聽num2;<br />聽聽聽聽聽聽聽聽if聽(聽!cin聽||聽num2聽<=聽50)<br />聽聽聽聽聽聽聽聽聽聽聽聽num2Valid聽=聽FALSE;<br />聽聽聽聽聽聽聽聽else<br />聽聽聽聽聽聽聽聽{<br />聽聽聽聽聽聽聽聽聽聽聽cout聽<<聽sqrt(float(num1聽+聽num2))聽<<聽endl;<br />聽聽聽聽聽聽聽聽聽聽聽loopCount++;<br />聽聽聽聽聽聽聽聽}<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">One could argue that the first version is easier to follow and understand than this second version. The primary task of the loop bodycomputing the square root of the sum of the numbersis more prominent in the first version. In the second version, the computation is obscured by being buried within nested Ifs. The second version also has a more complicated control flow.</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">The disadvantage of using </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">break</font><font face="Times New Roman, Times, Serif" size="3"> with loops is that it can become a crutch for those who are too impatient to think carefully about loop design. It's easy to overuse (and abuse) the technique. Here's an example, printing the integers 1 through 5:</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">i聽=聽1;<br />while聽(TRUE)<br />{<br />聽聽聽聽cout聽<<聽i;<br />聽聽聽聽if聽(i聽==聽5)<br />聽聽聽聽聽聽聽聽break;<br />聽聽聽聽i++;<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">There is no real justification for setting up the loop this way. Conceptually, it is a pure count-controlled loop, and a simple For loop does the job:</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">for聽(i聽=聽1;聽i聽<=聽5;聽i++)<br />聽聽聽聽cout聽<<聽i;</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_472.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_473</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_474.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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