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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_95</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_94.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_95</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_96.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 95</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="3">FREEZE_PT</font><font face="Times New Roman, Times, Serif" size="3"> and </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">BOIL_PT</font><font face="Times New Roman, Times, Serif" size="3"> are added first, and then their sum is divided by 2.0. We evaluate subexpressions in parentheses first and then follow the precedence of the operators.</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">When there are multiple arithmetic operators with the same precedence, their <i>grouping order</i> (or <i>associativity)</i> is from left to right. 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">int1聽聽-聽int2聽+聽int3</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">means </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">(int1 int2) + int3</font><font face="Times New Roman, Times, Serif" size="3">, not </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">int1 (int2 + int3</font><font face="Times New Roman, Times, Serif" size="3">). As another example, we would use 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">(float1聽+聽float2)聽/聽float聽1聽*聽3.0</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 evaluate the expression in parentheses first, then divide the sum by </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">float1</font><font face="Times New Roman, Times, Serif" size="3">, and multiply the result by 3.0. Below are some more examples.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table cellpadding="0" cellspacing="0" border="0" width="100%"><tr><td height="12"></td></tr><tr><td><table cellspacing="0" width="296" cellpadding="7"><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2"><i>Expression</i></font></td><td valign="top"><font face="Times New Roman, Times, Serif" size="2"><i>Value</i></font></td></tr><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2"></font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">10 / 2 * 3</font><font face="Times New Roman, Times, Serif" size="2"></font></td><td valign="top"><font face="Times New Roman, Times, Serif" size="2">15</font></td></tr><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2"></font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">10 % 3 - 4 / 2</font><font face="Times New Roman, Times, Serif" size="2"></font></td><td valign="top"><font face="Times New Roman, Times, Serif" size="2">-1</font></td></tr><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2"></font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">5.0 * 2.0 / 4.0 * 2.0</font><font face="Times New Roman, Times, Serif" size="2"></font></td><td valign="top"><font face="Times New Roman, Times, Serif" size="2">5.0</font></td></tr><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2"></font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">5.0 * 2.0 / (4.0 * 2.0)</font><font face="Times New Roman, Times, Serif" size="2"></font></td><td valign="top"><font face="Times New Roman, Times, Serif" size="2">1.25</font></td></tr><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2"></font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">5.0 + 2.0 / (4.0 * 2.0)</font><font face="Times New Roman, Times, Serif" size="2"></font></td><td valign="top"><font face="Times New Roman, Times, Serif" size="2">5.25</font></td></tr></table></td></tr></table><br /><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"><i>Type Coercion and Type Casting</i></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">Integer values and floating point values are stored differently inside a computer's memory. The pattern of bits that represents the constant 2 does not look at all like the pattern of bits representing the constant 2.0. (In Chapter 10, we examine why floating point numbers need a special representation inside the computer.) What happens if we mix integer and floating point values together in an assignment statement or an arithmetic expression? Let's look first at assignment statements.</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">Assignment Statements</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">If you make the declarations</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">int聽聽聽someInt;<br />float聽someFloat;</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_94.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_95</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_96.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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