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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_541</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_540.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_541</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_542.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 541</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">The only caution here is that when control exits the loop, the value of </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">patient</font><font face="Times New Roman, Times, Serif" size="3"> is one <i>greater than</i> the largest value in the domain (</font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">SHEEP</font><font face="Times New Roman, Times, Serif" size="3">). If you want to use </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">patient</font><font face="Times New Roman, Times, Serif" size="3"> outside the loop, you must reassign it a value that is within the appropriate range for the </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">Animals</font><font face="Times New Roman, Times, Serif" size="3"> type.</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">Comparison</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 most common operation performed on values of enumeration types is comparison. When you compare two values, their ordering is determined by the order in which you listed the enumerators in the type declaration. For instance, the expression</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">inPatient聽<=聽BIRD</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 TRUE if </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">inPatient</font><font face="Times New Roman, Times, Serif" size="3"> contains the value </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">RODENT</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">CAT</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">DOG,</font><font face="Times New Roman, Times, Serif" size="3"> or </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">BIRD</font><font face="Times New Roman, Times, Serif" size="3">.</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">You can also use values of an enumeration type in a Switch statement. Because </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">RODENT</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">CAT</font><font face="Times New Roman, Times, Serif" size="3">, and so on are literals, they can appear in case labels:</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(inPatient)<br />{<br />聽聽聽聽case聽RODENT聽聽:<br />聽聽聽聽case聽CAT聽聽聽聽聽:<br />聽聽聽聽case聽DOG聽聽聽聽聽:<br />聽聽聽聽case聽BIRD聽聽聽聽:聽cout聽<聽Cage聽ward;<br />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REPTILE聽:聽cout聽<聽Terrarium聽ward;<br />聽聽聽聽case聽HORSE聽聽聽:<br />聽聽聽聽case聽BOVINE聽聽:<br />聽聽聽聽case聽SHEEP聽聽聽:聽cout聽<Barn;<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">Input and Output</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">Stream I/O is defined only for the basic built-in types (</font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">int</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">float</font><font face="Times New Roman, Times, Serif" size="3">, and so on), not for enumeration types. Values of enumeration types must be input or output indirectly.</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">To input values, the usual strategy is to read a number or a letter code and translate it to one of the identifiers in the enumeration type. For example, the veterinary office program could read the kind of animal as a series of characters, then assign one of the values of type </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">Animals</font><font face="Times New Roman, Times, Serif" size="3"> to that patient. The following program fragment reads in an animal represented by its first two letters and converts it to one of the values in type </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">Animals</font><font face="Times New Roman, Times, Serif" size="3">.</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">cin聽>>聽ch1聽>>聽ch2;<br />switch聽(ch1)<br />{<br />聽聽聽聽case聽R聽:聽if聽(ch2聽==聽o)<br />聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽聽inPatient聽=聽RODENT;<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_540.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_541</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_542.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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