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<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font LANG="ZH-CN" size="2">程序运行结果是：</font></p>
<blockquote>
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">12345
54321</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">54321
12345</font></p>
</blockquote>
</blockquote>
<font SIZE="3">
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font LANG="ZH-CN" size="2">由于引用是“别名”，实参与形参之间不是值传递，而是一种“映射”，所以对形参的改变，实际上就是对实参的改变。</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 10; margin-bottom: 0"><font size="2">(2)
<font LANG="ZH-CN">用引用返回值</font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"><font LANG="ZH-CN">【例</font>2-16<font LANG="ZH-CN">】用“引用”返回值。</font></font></p>
<blockquote>
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">#include
"iostream.h"</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">float
temp;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">float
fn1(float r)</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">{
temp=r*r*3.14;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">return
temp;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">}</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">float
& fn2(float r)</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">{
temp=r*r*3.14;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">return
temp;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">}</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">void
main( )</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">{
float a=fn1(5.0);</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"> //float
&b=fn1(5.0); <font color="#FF0000">//error<font LANG="ZH-CN">：函数</font>fn1<font LANG="ZH-CN">的返回类型是</font>float<font LANG="ZH-CN">，不是</font>float&</font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"> float
c=fn2(5.0);</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"> float
&d=fn2(5.0);</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2"> cout<<a<<"
"<<c<<" "<<d<<endl;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">}</font></p>
</blockquote>
</blockquote>
<font SIZE="3">
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font LANG="ZH-CN" size="2">程序运行结果是：</font></p>
<blockquote>
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">78.5
78.5 78.5</font></p>
</blockquote>
</blockquote>
<font SIZE="3">
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font size="2"><font LANG="ZH-CN">如果把变量</font>temp<font LANG="ZH-CN">设置成局部的：</font></font></p>
<blockquote>
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">#include
"iostream.h"</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">//float
temp;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">float
fn1(float r)</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">{
float temp;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">temp=r*r*3.14;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">return
temp;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">}</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">float
& fn2(float r)</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">{
float temp;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">temp=r*r*3.14;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">return
temp; <font color="#FF6600">//<font LANG="ZH-CN">注意：返回一个局部变量的地址</font></font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">}</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">void
main( )</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">{
float a=fn1(5.0);</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">//float
&b=fn1(5.0); <font color="#FF0000">//<font LANG="ZH-CN">错误：</font>float<font LANG="ZH-CN">与</font>float&<font LANG="ZH-CN">之间的类型不能转换</font></font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">float
c=fn2(5.0);</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">float
&d=fn2(5.0); <font color="#FF0000">//<font LANG="ZH-CN">危险：</font>d<font LANG="ZH-CN">引用到一个局部变量上</font></font></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">cout<<a<<"
"<<c<<" "<<d<<endl;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">}</font></p>
</blockquote>
</blockquote>
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