📄 perl 语言－perl 中文教程（第三章）.htm
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$dividend / $divisor);<BR> PERL
5中，还可以在赋值式左边使用条件操作符来选择被赋值的变量，如：<BR> $condvar == 43 ? $var1 :
$var2 = 14;<BR> $condvar == 43 ? $var1 = 14 : $var2 =
14;<BR><BR><A name=十一、操作符的次序>十一、操作符的次序</A> <BR></P>
<P align=center><B>Table 3.6.</B> 操作符次序</P>
<DIV align=center>
<CENTER>
<TABLE borderColor=forestgreen cellSpacing=0 cellPadding=2 width="65%"
border=1>
<TBODY>
<TR>
<TD class=myFont vAlign=top width=214><B>操作符</B></TD>
<TD class=myFont vAlign=top width=310><B>描述</B></TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>++</TT>, <TT>--</TT> </TD>
<TD class=myFont vAlign=top width=310>自增，自减</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>-</TT>, <TT>~</TT>,
<TT>!</TT> </TD>
<TD class=myFont vAlign=top width=310>单目</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>**</TT> </TD>
<TD class=myFont vAlign=top width=310>乘方</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>=~</TT>, <TT>!~</TT> </TD>
<TD class=myFont vAlign=top width=310>模式匹配</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>*</TT>, <TT>/</TT>,
<TT>%</TT>, <TT>x</TT> </TD>
<TD class=myFont vAlign=top width=310>乘，除，取余，重复</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>+</TT>, <TT>-</TT>,
<TT>.</TT> </TD>
<TD class=myFont vAlign=top width=310>加，减，联接</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT><<</TT>,
<TT>>></TT> </TD>
<TD class=myFont vAlign=top width=310>移位</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>-e</TT>, <TT>-r</TT>, etc.
</TD>
<TD class=myFont vAlign=top width=310>文件状态</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT><</TT>, <TT><=</TT>,
<TT>></TT>, <TT>>=</TT>, <TT>lt</TT>, <TT>le</TT>,
<TT>gt</TT>, <TT>ge</TT> </TD>
<TD class=myFont vAlign=top width=310>不等比较</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>==</TT>, <TT>!=</TT>,
<TT><=></TT>, <TT>eq</TT>, <TT>ne</TT>, <TT>cmp</TT> </TD>
<TD class=myFont vAlign=top width=310>相等比较</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>&</TT> </TD>
<TD class=myFont vAlign=top width=310>位与</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>|</TT>, <TT>^</TT> </TD>
<TD class=myFont vAlign=top width=310>位或，位异或</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>&&</TT> </TD>
<TD class=myFont vAlign=top width=310>逻辑与</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>||</TT> </TD>
<TD class=myFont vAlign=top width=310>逻辑或</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>..</TT> </TD>
<TD class=myFont vAlign=top width=310>列表范围</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>?</TT> and <TT>:</TT> </TD>
<TD class=myFont vAlign=top width=310>条件操作符</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>=</TT>, <TT>+=</TT>,
<TT>-=</TT>, <TT>*=</TT>, </TD>
<TD class=myFont vAlign=top width=310>赋值</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214>and so on</TD>
<TD class=myFont vAlign=top width=310> </TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>,</TT></TD>
<TD class=myFont vAlign=top width=310>逗号操作符</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>not</TT> </TD>
<TD class=myFont vAlign=top width=310>Low-precedence logical
NOT</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>and</TT> </TD>
<TD class=myFont vAlign=top width=310>Low-precedence logical
AND</TD></TR>
<TR>
<TD class=myFont vAlign=top width=214><TT>or</TT>, <TT>xor</TT> </TD>
<TD class=myFont vAlign=top width=310>Low-precedence logical OR and
XOR</TD></TR></TBODY></TABLE></CENTER></DIV>
<P>.操作符结合性(associativity)：<BR></P>
<P align=center><B>Table 3.7. 操作符结合性</B></P>
<DIV align=center>
<CENTER>
<TABLE borderColor=forestgreen cellSpacing=0 cellPadding=2 width="65%"
border=1>
<TBODY>
<TR>
<TD class=myFont vAlign=top width=240><B>操作符</B></TD>
<TD class=myFont vAlign=top width=240><B>结合性</B></TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>++</TT>, <TT>--</TT> </TD>
<TD class=myFont vAlign=top width=240>无</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>-</TT>, <TT>~</TT>,
<TT>!</TT> </TD>
<TD class=myFont vAlign=top width=240>Right-to-left</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>**</TT> </TD>
<TD class=myFont vAlign=top width=240>Right-to-left</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>=~</TT>, <TT>!~</TT> </TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>*</TT>, <TT>/</TT>,
<TT>%</TT>, <TT>x</TT> </TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>+</TT>, <TT>-</TT>,
<TT>.</TT> </TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT><<</TT>,
<TT>>></TT> </TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>-e</TT>, <TT>-r</TT>, </TD>
<TD class=myFont vAlign=top width=240>无</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT><</TT>, <TT><=</TT>,
<TT>></TT>, <TT>>=</TT>, <TT>lt</TT>, <TT>le</TT>,
<TT>gt</TT>, <TT>ge</TT> </TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>==</TT>, <TT>!=</TT>,
<TT><=></TT>, <TT>eq</TT>, <TT>ne</TT>, <TT>cmp</TT> </TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>&</TT> </TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>|</TT>, <TT>^</TT> </TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>&&</TT> </TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>||</TT> </TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>..</TT> </TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>?</TT> and <TT>:</TT> </TD>
<TD class=myFont vAlign=top width=240>Right-to-left</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>=</TT>, <TT>+=</TT>,
<TT>-=</TT>, <TT>*=</TT>, </TD>
<TD class=myFont vAlign=top width=240>Right-to-left</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240>and so on</TD>
<TD class=myFont vAlign=top width=240> </TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>,</TT></TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>not</TT> </TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>and</TT> </TD>
<TD class=myFont vAlign=top width=240>Left-to-right</TD></TR>
<TR>
<TD class=myFont vAlign=top width=240><TT>or</TT>, <TT>xor</TT> </TD>
<TD class=myFont vAlign=top
width=240>Left-to-right</TD></TR></TBODY></TABLE></CENTER></DIV>
<P><BR><BR>建议：<BR> 1、当你不确定某操作符是否先执行时，一定要用括号明确之。<BR> 2、用多行、空格等方式提高程序的可读性。</P></TD></TR></TBODY></TABLE>
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