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Ref-docs/c_lib_guide/1.5.html
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<html>
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<head>
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<title>
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C Guide--1.5 Operators
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</title>
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<!-- Changed by: eric huss, 12-Mar-1997 -->
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</head>
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<body text="#000000" bgcolor="#FFFFFF">
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<center>
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<table border=0 width=100%>
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<tr>
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||||
<td align=left width=20% valign=top>
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<a href="1.4.html">
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<img src="left.gif" border=0>
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Previous Section<br>
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1.4 References</a></td>
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<td align=center width=60% valign=top>
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||||
| <a href="index.html">Table of Contents</a> |
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<a href="index2.html">Index</a> |</td>
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<td align=right width=20% valign=top>
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<a href="1.6.html">
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Next Section
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<img src="right.gif" border=0><br>
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1.6 Statements</a></td>
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</tr>
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</table>
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</center>
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<hr>
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<h1>1.5.1 Postfix</h1>
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<p>
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Postfix operators are operators that are suffixed to an expression.
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<blockquote>
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<i>operand</i><code><b>++;</b></code><br>
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This causes the value of the <i>operand</i> to be returned. After the result is obtained, the
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value of the operand is incremented by 1.
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</blockquote>
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<blockquote>
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<i>operand</i><code><b>--;</b></code><br>
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This is the same but the value of the operand is decremented by 1.
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</blockquote>
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<p>
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Examples:
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<blockquote><code><b>
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int joe=3;<br>
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joe++;</b></code>
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</blockquote>
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The value of <code><b>joe</b></code> is now 4.
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<blockquote><code><b>
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printf("%i",joe++);</b></code>
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</blockquote>
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This outputs the number 4. The value of <code><b>joe</b></code> is now 5.
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<h1> 1.5.2 Unary and Prefix</h1>
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<p>
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Prefix operators are operators that are prefixed to an expression.
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<blockquote>
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<code><b>++</b></code><i>operand</i><code><b>;</b></code><br>
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This causes the value of the operand to be incremented by 1. Its new value is then
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returned.
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</blockquote>
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<blockquote>
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<code><b>--</b></code><i>operand</i><code><b>;</b></code><br>
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This is the same but the value of the operand is decremented by 1.
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</blockquote>
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<blockquote>
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<code><b>!</b></code><i>operand</i><br>
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Returns the logical NOT operation on the operand. A true operand returns false, a false
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operand returns true. Also known as the bang operand.
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</blockquote>
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<blockquote>
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<code><b>~</b></code><i>operand</i><br>
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Returns the compliment of the operand. The returned value is the operand with its bits
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reversed (1's become 0's, 0's become 1's).
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</blockquote>
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<p>
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Examples:
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<blockquote>
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<code><b>int bart=7;<br>
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printf("%i",--bart);</b></code><br>
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This outputs the number 6. The value of bart is now 6.<br>
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<br>
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<code><b>int lisa=1;<br>
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printf("%i",!lisa);</b></code><br>
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This outputs 0 (false).
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</blockquote>
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<h1>1.5.3 Normal</h1>
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<p>
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There are several normal operators which return the result defined for each:
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<blockquote>
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<i>expression1</i><code><b> + </b></code><i>expression</i><br>
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The result of this is the sum of the two expressions.<br>
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<br>
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<i>expression1</i><code><b> - </b></code><i>expression2</i><br>
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The result of this is the value of <i>expression2</i> subtracted from <i>expression1</i>.
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<br>
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<br>
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<i>expression1</i><code><b> * </b></code><i>expression2</i><br>
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The result of this is the value of <i>expression1</i> multiplied by <i>expression2</i>.
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<br>
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<br>
|
||||
<i>expression1</i><code><b> / </b></code><i>expression2</i><br>
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The result of this is the value of <i>expression1</i> divided by <i>expression2</i>.
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<br>
|
||||
<br>
|
||||
<i>expression1</i><code><b> % </b></code><i>expression2</i><br>
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The result of this is the value of the remainder after dividing <i>expression1</i> by <i>expression2</i>.
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Also called the modulo operator.
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<br>
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<br>
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<i>expression1</i><code><b> & </b></code><i>expression2</i><br>
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Returns a bitwise AND operation done on <i>expression1</i> and <i>expression2</i>. The result is a
|
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value the same size as the expressions with its bits modified using the following rules: Both bits
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must be 1 (on) to result in 1 (on), otherwise the result is 0 (off).
|
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<br>
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<center>
|
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<table border=1>
|
||||
<tr>
|
||||
<th>e1</th>
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<th>e2</th>
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||||
<th>Result</th>
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||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>0</td>
|
||||
<td>1</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>1</td>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>1</td>
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||||
<td>1</td>
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||||
<td>1</td>
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</tr>
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</table>
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</center>
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<br>
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<i>expression1</i><code><b> | </b></code><i>expression2</i><br>
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Returns a bitwise OR operation done on <i>expression1</i> and <i>expression2</i>. The result is a
|
||||
value the same size as the expressions with its bits modified using the following rules: Both bits
|
||||
must be 0 (off) to result in 0 (off), otherwise the result is 1 (on).
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<br>
|
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<center>
|
||||
<table border=1>
|
||||
<tr>
|
||||
<th>e1</th>
|
||||
<th>e2</th>
|
||||
<th>Result</th>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>0</td>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>1</td>
|
||||
<td>0</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
<td>1</td>
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||||
</tr>
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||||
</table>
|
||||
</center>
|
||||
<br>
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||||
<i>expression1</i><code><b> ^ </b></code><i>expression2</i><br>
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Returns a bitwise XOR operation done on <i>expression1</i> and <i>expression2</i>. The result is a
|
||||
value the same size as the expressions with its bits modified using the following rules: If both
|
||||
bits are the same, then the result is 0 (off), otherwise the result is 1 (on).
|
||||
<br>
|
||||
<center>
|
||||
<table border=1>
|
||||
<tr>
|
||||
<th>e1</th>
|
||||
<th>e2</th>
|
||||
<th>Result</th>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>0</td>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>1</td>
|
||||
<td>0</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
<td>0</td>
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||||
</tr>
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||||
</table>
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</center>
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<br>
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<i>expression1</i><code><b> >> </b></code><i>shift_value</i><br>
|
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Returns <i>expression1</i> with its bits shifted to the right by the <i>shift_value</i>. The leftmost bits
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||||
are replaced with zeros if the value is nonnegative or unsigned. This result is the integer part of
|
||||
<i>expression1</i> divided by 2 raised to the power of <i>shift_value</i>. If <i>expression1</i> is signed, then the
|
||||
result is implementation specific.
|
||||
<br>
|
||||
<br>
|
||||
<i>expression1</i><code><b> << </b></code><i>shift_value</i><br>
|
||||
Returns <i>expression1</i> with its bits shifted to the left by the <i>shift_value</i>. The rightmost bits
|
||||
are replaced with zeros. This result is the value of <i>expression1</i> multiplied by the value of 2
|
||||
raised to the power of <i>shift_value</i>. If <i>expression1</i> is signed, then the result is implementation
|
||||
specific.
|
||||
</blockquote>
|
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<h1> 1.5.4 Boolean</h1>
|
||||
<p>
|
||||
The boolean operators return either 1 (true) or 0 (false).
|
||||
<blockquote>
|
||||
<i>expression1</i><code><b> && </b></code><i>expression2</i><br>
|
||||
Returns the logical AND operation of <i>expression1</i> and <i>expression2</i>. The result is 1 (true)
|
||||
if both expressions are true, otherwise the result is 0 (false).
|
||||
<br>
|
||||
<center>
|
||||
<table border=1>
|
||||
<tr>
|
||||
<th>e1</th>
|
||||
<th>e2</th>
|
||||
<th>Result</th>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>0</td>
|
||||
<td>1</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>1</td>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
</table>
|
||||
</center>
|
||||
<br>
|
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<i>expression1</i><code><b> || </b></code><i>expression2</i>
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<br>
|
||||
Returns the logical OR operation of <i>expression1</i> and <i>expression2</i>. The result is 0 (false)
|
||||
if bother expressions are false, otherwise the result is 1 (true).
|
||||
<br>
|
||||
<center>
|
||||
<table border=1>
|
||||
<tr>
|
||||
<th>e1</th>
|
||||
<th>e2</th>
|
||||
<th>Result</th>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>0</td>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>1</td>
|
||||
<td>0</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
</table>
|
||||
</center>
|
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|
||||
<br>
|
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<i>expression1</i><code><b> < </b></code><i>expression2</i>
|
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<br>
|
||||
Returns 1 (true) if <i>expression1</i> is less than <i>expression2</i>, otherwise the result is 0 (false).
|
||||
<br>
|
||||
|
||||
<br>
|
||||
<i>expression1</i><code><b> > </b></code><i>expression2</i>
|
||||
<br>
|
||||
Returns 1 (true) if <i>expression1</i> is greater than <i>expression2</i>, otherwise the result is 0
|
||||
(false).
|
||||
<br>
|
||||
|
||||
<br>
|
||||
<i>expression1</i><code><b> <= </b></code><i>expression2</i>
|
||||
<br>
|
||||
Returns 1 (true) if <i>expression1</i> is less than or equal to <i>expression2</i>, otherwise the result is
|
||||
0 (false).
|
||||
<br>
|
||||
|
||||
<br>
|
||||
<i>expression1</i><code><b> >= </b></code><i>expression2</i>
|
||||
<br>
|
||||
Returns 1 (true) if <i>expression1</i> is greater than or equal to <i>expression2</i>, otherwise the
|
||||
result is 0 (false).
|
||||
<br>
|
||||
|
||||
<br>
|
||||
<i>expression1</i><code><b> == </b></code><i>expression2</i>
|
||||
<br>
|
||||
Returns 1 (true) if <i>expression1</i> is equal to <i>expression2</i>, otherwise the result is 0 (false).
|
||||
<br>
|
||||
|
||||
<br>
|
||||
<i>expression1</i><code><b> != </b></code><i>expression2</i>
|
||||
<br>
|
||||
Returns 1 (true) if <i>expression</i>1 is not equal to <i>expression2</i>, otherwise the result is 0
|
||||
(false).
|
||||
<br>
|
||||
</blockquote>
|
||||
|
||||
<h1> 1.5.5 Assignment</h1>
|
||||
<p>
|
||||
An assignment operator stores the value of the right expression into the left expression.
|
||||
<blockquote>
|
||||
<i>expression1</i><code><b> = </b></code><i>expression2</i><br>
|
||||
The value of <i>expression2</i> is stored in <i>expression1</i>.<br>
|
||||
<br>
|
||||
<i>expression1</i><code><b> *= </b></code><i>expression2</i><br>
|
||||
The value of <i>expression1</i> times <i>expression2</i> is stored in <i>expression1</i>.<br>
|
||||
<br>
|
||||
<i>expression1</i><code><b> /= </b></code><i>expression2</i><br>
|
||||
The value of <i>expression1</i> divided by <i>expression2</i> is stored in <i>expression1</i>.<br>
|
||||
<br>
|
||||
<i>expression1</i><code><b> %= </b></code><i>expression2</i><br>
|
||||
The value of the remainder of <i>expression1</i> divided by <i>expression2</i> is stored in
|
||||
<i>expression1</i>.<br>
|
||||
<br>
|
||||
<i>expression1</i><code><b> += </b></code><i>expression2</i><br>
|
||||
The value of <i>expression1</i> plus <i>expression2</i> is stored in <i>expression1</i>.<br>
|
||||
<br>
|
||||
<i>expression1</i><code><b> -= </b></code><i>expression2</i><br>
|
||||
The value of <i>expression1</i> minus <i>expression2</i> is stored in <i>expression1</i>.<br>
|
||||
<br>
|
||||
<i>expression1</i><code><b> <<= </b></code><i>shift_value</i><br>
|
||||
The value of <i>expression1</i>'s bits are shifted to the left by <i>shift_value</i> and stored in
|
||||
<i>expression1</i>.<br>
|
||||
<br>
|
||||
<i>expression1</i><code><b> >>= </b></code><i>shift_value</i><br>
|
||||
The value of <i>expression1</i>'s bits are shifted to the right by <i>shift_value</i> and stored in
|
||||
<i>expression1</i>.<br>
|
||||
<br>
|
||||
<i>expression1</i><code><b> &= </b></code><i>expression2</i><br>
|
||||
The value of the bitwise AND of <i>expression1</i> and <i>expression2</i> is stored in <i>expression1</i>.<br>
|
||||
<center>
|
||||
<table border=1>
|
||||
<tr>
|
||||
<th>e1</th>
|
||||
<th>e2</th>
|
||||
<th>Result</th>
|
||||
</tr>
|
||||
<tr align=center>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr align=center>
|
||||
<td>0</td>
|
||||
<td>1</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr align=center>
|
||||
<td>1</td>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr align=center>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
</table>
|
||||
</center>
|
||||
<br>
|
||||
<i>expression1</i><code><b> ^= </b></code><i>expression2</i><br>
|
||||
The value of the bitwise XOR of <i>expression1</i> and <i>expression2</i> is stored in <i>expression1</i>.<br>
|
||||
<center>
|
||||
<table border=1>
|
||||
<tr>
|
||||
<th>e1</th>
|
||||
<th>e2</th>
|
||||
<th>Result</th>
|
||||
</tr>
|
||||
<tr align=center>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr align=center>
|
||||
<td>0</td>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
<tr align=center>
|
||||
<td>1</td>
|
||||
<td>0</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
<tr align=center>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
</table>
|
||||
</center>
|
||||
<br>
|
||||
<i>expression1</i><code><b> |= </b></code><i>expression2</i><br>
|
||||
The value of the bitwise OR of <i>expression1</i> and <i>expression2</i> is stored in <i>expression1</i>.<br>
|
||||
<center>
|
||||
<table border=1>
|
||||
<tr>
|
||||
<th>e1</th>
|
||||
<th>e2</th>
|
||||
<th>Result</th>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
<td>0</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>0</td>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>1</td>
|
||||
<td>0</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
<tr ALIGN=CENTER>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
<td>1</td>
|
||||
</tr>
|
||||
</table>
|
||||
</center>
|
||||
</blockquote>
|
||||
<br>
|
||||
<h1> 1.5.6 Precedence</h1>
|
||||
<p>
|
||||
The operators have a set order of precedence during evaluation. Items encapsulated in
|
||||
parenthesis are evaluated first and have the highest precedence. The following chart shows the
|
||||
order of precedence with the items at the top having highest precedence.
|
||||
<p>
|
||||
<center>
|
||||
<table>
|
||||
<tr>
|
||||
<th>Operator</th>
|
||||
<th>Name</th>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>!</td>
|
||||
<td>Logical NOT. Bang.</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>++ --</td>
|
||||
<td>Increment and decrement operators.</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>* / %</td>
|
||||
<td>Multiplicative operators.</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>+ -</td>
|
||||
<td>Additive operators.</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><< >></td>
|
||||
<td>Shift operators.</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>< > <= >=</td>
|
||||
<td>Inequality comparators.</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>== !=</td>
|
||||
<td>Equality comparators</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>&</td>
|
||||
<td>Bitwise AND.</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>^</td>
|
||||
<td>Bitwise XOR.</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>|</td>
|
||||
<td>Bitwise OR.</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>&&</td>
|
||||
<td>Logical AND.</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>||</td>
|
||||
<td>Logical OR.</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>?:</td>
|
||||
<td>Conditional.</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td>= <i>op</i>=</td>
|
||||
<td>Assignment.</td>
|
||||
</tr>
|
||||
</table>
|
||||
</center>
|
||||
<p>
|
||||
Examples:
|
||||
<blockquote><code><b>
|
||||
17 * 5 + !(1+1) && 0
|
||||
</b></code></blockquote>
|
||||
Evaluates to 0 (false).
|
||||
<blockquote><code><b>
|
||||
5+7<4
|
||||
</b></code></blockquote>
|
||||
Evaluates to 1 (true).
|
||||
<blockquote><code><b>
|
||||
a<b<c
|
||||
</b></code></blockquote>
|
||||
Same as (a<b)<c.
|
||||
<hr>
|
||||
|
||||
<center>
|
||||
<table border=0 width=100%>
|
||||
<tr>
|
||||
<td align=left width=20% valign=top>
|
||||
<a href="1.4.html">
|
||||
<img src="left.gif" border=0>
|
||||
Previous Section<br>
|
||||
1.4 References</a></td>
|
||||
<td align=center width=60% valign=top>
|
||||
| <a href="index.html">Table of Contents</a> |
|
||||
<a href="index2.html">Index</a> |</td>
|
||||
<td align=right width=20% valign=top>
|
||||
<a href="1.6.html">
|
||||
Next Section
|
||||
<img src="right.gif" border=0><br>
|
||||
1.6 Statements</a></td>
|
||||
</tr>
|
||||
</table>
|
||||
</center>
|
||||
|
||||
</body>
|
||||
</html>
|
||||
Reference in New Issue
Block a user