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📄 subroutines.mht

📁 Perl 编程技巧大全。适合初学者阅读。
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Subject: Subroutines
Date: Wed, 29 Apr 2009 09:26:56 +0800
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<DIV class=3DSECT1>
<H1 class=3DSECT1><A name=3DSUBROUTINES>10. Subroutines</A></H1>
<DIV class=3DSECT2>
<H2 class=3DSECT2><A name=3DAEN536>Introduction</A></H2>
<TABLE width=3D"100%" bgColor=3D#2f4f4f border=3D0>
  <TBODY>
  <TR>
    <TD><PRE class=3DSCREEN><FONT color=3D#f5deb3 size=3D+1><FONT =
color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT =
color=3D#b2dfee>hello</FONT> <FONT color=3D#00ffff>{</FONT><FONT =
color=3D#43cd80> </FONT>
    $greeted++<FONT color=3D#00ffff>;</FONT>          <FONT =
color=3D#bebebe># global variable</FONT><FONT color=3D#43cd80> =
</FONT><FONT color=3D#bebebe>
</FONT>    <FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"hi =
there!\n"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>hello<FONT color=3D#00ffff>();</FONT>                 <FONT =
color=3D#bebebe># call subroutine hello with no arguments/parameters
#-----------------------------
</FONT></PRE></FONT></TD></TR></TBODY></TABLE></DIV>
<DIV class=3DSECT2>
<H2 class=3DSECT2><A name=3DAEN539>Accessing Subroutine =
Arguments</A></H2>
<TABLE width=3D"100%" bgColor=3D#2f4f4f border=3D0>
  <TBODY>
  <TR>
    <TD><PRE class=3DSCREEN><FONT color=3D#f5deb3 size=3D+1><FONT =
color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT =
color=3D#b2dfee>hypotenuse</FONT> <FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>return</FONT> <FONT =
color=3D#98fb98>sqrt</FONT><FONT color=3D#00ffff>(</FONT> <FONT =
color=3D#00ffff>(</FONT><FONT color=3D#cdad00>$_</FONT><FONT =
color=3D#00ffff>[</FONT><FONT color=3D#cdcd00>0</FONT><FONT =
color=3D#00ffff>]</FONT> ** <FONT color=3D#cdcd00>2</FONT><FONT =
color=3D#00ffff>)</FONT> + <FONT color=3D#00ffff>(</FONT><FONT =
color=3D#cdad00>$_</FONT><FONT color=3D#00ffff>[</FONT><FONT =
color=3D#cdcd00>1</FONT><FONT color=3D#00ffff>]</FONT> ** <FONT =
color=3D#cdcd00>2</FONT><FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>);</FONT>
<FONT color=3D#00ffff>}</FONT>

$diag =3D hypotenuse<FONT color=3D#00ffff>(</FONT><FONT =
color=3D#cdcd00>3</FONT>,<FONT color=3D#cdcd00>4</FONT><FONT =
color=3D#00ffff>);</FONT>  <FONT color=3D#bebebe># $diag is 5
#-----------------------------
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT =
color=3D#b2dfee>hypotenuse</FONT> <FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT color=3D#00ffff>(</FONT><FONT =
color=3D#9ac0cd>$side1</FONT>, <FONT color=3D#9ac0cd>$side2</FONT><FONT =
color=3D#00ffff>)</FONT> =3D <FONT color=3D#cdad00>@_</FONT><FONT =
color=3D#00ffff>;</FONT>
    <FONT color=3D#ffa500>return</FONT> <FONT =
color=3D#98fb98>sqrt</FONT><FONT color=3D#00ffff>(</FONT> <FONT =
color=3D#00ffff>(</FONT>$side1 ** <FONT color=3D#cdcd00>2</FONT><FONT =
color=3D#00ffff>)</FONT> + <FONT color=3D#00ffff>(</FONT>$side2 ** <FONT =
color=3D#cdcd00>2</FONT><FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>);</FONT>
<FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ff7f50>print</FONT> hypotenuse<FONT =
color=3D#00ffff>(</FONT><FONT color=3D#cdcd00>3</FONT>, <FONT =
color=3D#cdcd00>4</FONT><FONT color=3D#00ffff>)</FONT>, <FONT =
color=3D#00cd00>"\n"</FONT><FONT color=3D#00ffff>;</FONT>               =
<FONT color=3D#bebebe># prints 5
</FONT>
<FONT color=3D#cdad00>@a</FONT> =3D <FONT color=3D#00ffff>(</FONT><FONT =
color=3D#cdcd00>3</FONT>, <FONT color=3D#cdcd00>4</FONT><FONT =
color=3D#00ffff>);</FONT>
<FONT color=3D#ff7f50>print</FONT> hypotenuse<FONT =
color=3D#00ffff>(</FONT><FONT color=3D#cdad00>@a</FONT><FONT =
color=3D#00ffff>)</FONT>, <FONT color=3D#00cd00>"\n"</FONT><FONT =
color=3D#00ffff>;</FONT>                 <FONT color=3D#bebebe># prints =
5
#-----------------------------
</FONT><FONT color=3D#cdad00>@both</FONT> =3D <FONT =
color=3D#00ffff>(</FONT><FONT color=3D#cdad00>@men</FONT>, <FONT =
color=3D#cdad00>@women</FONT><FONT color=3D#00ffff>);</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#cdad00>@nums</FONT> =3D <FONT =
color=3D#00ffff>(</FONT><FONT color=3D#cdcd00>1.4</FONT>, <FONT =
color=3D#cdcd00>3.5</FONT>, <FONT color=3D#cdcd00>6.7</FONT><FONT =
color=3D#00ffff>);</FONT>
<FONT color=3D#cdad00>@ints</FONT> =3D <FONT =
color=3D#98fb98>int</FONT>_all<FONT color=3D#00ffff>(</FONT><FONT =
color=3D#cdad00>@nums</FONT><FONT color=3D#00ffff>);</FONT>        <FONT =
color=3D#bebebe># </FONT><FONT color=3D#cdad00>@nums</FONT><FONT =
color=3D#bebebe> unchanged
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT =
color=3D#98fb98>int</FONT>_all <FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT =
color=3D#cdad00>@retlist</FONT> =3D <FONT color=3D#cdad00>@_</FONT><FONT =
color=3D#00ffff>;</FONT>          <FONT color=3D#bebebe># make safe copy =
for return
</FONT>    <FONT color=3D#ffa500>for</FONT> <FONT =
color=3D#ffa500>my</FONT> $n <FONT color=3D#00ffff>(</FONT><FONT =
color=3D#cdad00>@retlist</FONT><FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT> $n =3D <FONT color=3D#98fb98>int</FONT><FONT =
color=3D#00ffff>(</FONT>$n<FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>}</FONT><FONT color=3D#43cd80> </FONT>
    <FONT color=3D#ffa500>return</FONT> <FONT =
color=3D#cdad00>@retlist</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT><FONT color=3D#43cd80> </FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#cdad00>@nums</FONT> =3D <FONT =
color=3D#00ffff>(</FONT><FONT color=3D#cdcd00>1.4</FONT>, <FONT =
color=3D#cdcd00>3.5</FONT>, <FONT color=3D#cdcd00>6.7</FONT><FONT =
color=3D#00ffff>);</FONT>
trunc_em<FONT color=3D#00ffff>(</FONT><FONT =
color=3D#cdad00>@nums</FONT><FONT color=3D#00ffff>);</FONT>              =
 <FONT color=3D#bebebe># </FONT><FONT color=3D#cdad00>@nums</FONT><FONT =
color=3D#bebebe> now (1,3,6)
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT =
color=3D#b2dfee>trunc_em</FONT> <FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>for</FONT> <FONT color=3D#00ffff>(</FONT><FONT =
color=3D#cdad00>@_</FONT><FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT> $_ =3D <FONT color=3D#98fb98>int</FONT><FONT =
color=3D#00ffff>(</FONT>$_<FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>}</FONT>  <FONT color=3D#bebebe># truncate each argument
</FONT><FONT color=3D#00ffff>}</FONT><FONT color=3D#43cd80> </FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>$line =3D <FONT color=3D#ff7f50>chomp</FONT><FONT =
color=3D#00ffff>(</FONT>&lt;&gt;<FONT color=3D#00ffff>);</FONT>          =
        <FONT color=3D#bebebe># WRONG
#-----------------------------
</FONT></PRE></FONT></TD></TR></TBODY></TABLE></DIV>
<DIV class=3DSECT2>
<H2 class=3DSECT2><A name=3DAEN542>Making Variables Private to a =
Function</A></H2>
<TABLE width=3D"100%" bgColor=3D#2f4f4f border=3D0>
  <TBODY>
  <TR>
    <TD><PRE class=3DSCREEN><FONT color=3D#f5deb3 size=3D+1><FONT =
color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT =
color=3D#b2dfee>somefunc</FONT> <FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT =
color=3D#9ac0cd>$variable</FONT><FONT color=3D#00ffff>;</FONT>           =
      <FONT color=3D#bebebe># $variable is invisible outside somefunc()
</FONT>    <FONT color=3D#ffa500>my</FONT> <FONT =
color=3D#00ffff>(</FONT><FONT color=3D#9ac0cd>$another</FONT>, <FONT =
color=3D#cdad00>@an_array</FONT>, <FONT =
color=3D#cdcd00>%a_hash</FONT><FONT color=3D#00ffff>);</FONT>     <FONT =
color=3D#bebebe># declaring many variables at once
</FONT>
    <FONT color=3D#bebebe># ...
</FONT><FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>my</FONT> <FONT =
color=3D#00ffff>(</FONT><FONT color=3D#9ac0cd>$name</FONT>, <FONT =
color=3D#9ac0cd>$age</FONT><FONT color=3D#00ffff>)</FONT> =3D <FONT =
color=3D#cdad00>@ARGV</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#ffa500>my</FONT> <FONT color=3D#9ac0cd>$start</FONT>      =
  =3D fetch_<FONT color=3D#98fb98>time</FONT><FONT =
color=3D#00ffff>();</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>my</FONT> <FONT =
color=3D#00ffff>(</FONT><FONT color=3D#9ac0cd>$a</FONT>, <FONT =
color=3D#9ac0cd>$b</FONT><FONT color=3D#00ffff>)</FONT> =3D <FONT =
color=3D#cdad00>@pair</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#ffa500>my</FONT> <FONT color=3D#9ac0cd>$c</FONT> =3D =
fetch_<FONT color=3D#98fb98>time</FONT><FONT color=3D#00ffff>();</FONT>

<FONT color=3D#ffa500>sub</FONT> check_<FONT color=3D#98fb98>x</FONT> =
<FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT color=3D#9ac0cd>$x</FONT> =3D =
<FONT color=3D#cdad00>$_</FONT><FONT color=3D#00ffff>[</FONT><FONT =
color=3D#cdcd00>0</FONT><FONT color=3D#00ffff>];</FONT><FONT =
color=3D#43cd80>       </FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT color=3D#9ac0cd>$y</FONT> =3D =
<FONT color=3D#00cd00>"whatever"</FONT><FONT =
color=3D#00ffff>;</FONT><FONT color=3D#43cd80>  </FONT>
    run_check<FONT color=3D#00ffff>();</FONT>
    <FONT color=3D#ffa500>if</FONT> <FONT =
color=3D#00ffff>(</FONT>$condition<FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT>
        <FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"got =
$x\n"</FONT><FONT color=3D#00ffff>;</FONT>
    <FONT color=3D#00ffff>}</FONT>
<FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>sub</FONT> <FONT =
color=3D#b2dfee>save_array</FONT> <FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT =
color=3D#cdad00>@arguments</FONT> =3D <FONT =
color=3D#cdad00>@_</FONT><FONT color=3D#00ffff>;</FONT>
    <FONT color=3D#ff7f50>push</FONT><FONT color=3D#00ffff>(</FONT><FONT =
color=3D#cdad00>@Global_Array</FONT>, \<FONT =
color=3D#cdad00>@arguments</FONT><FONT color=3D#00ffff>);</FONT>
<FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT></PRE></FONT></TD></TR></TBODY></TABLE></DIV>
<DIV class=3DSECT2>
<H2 class=3DSECT2><A name=3DAEN545>Creating Persistent Private =
Variables</A></H2>
<TABLE width=3D"100%" bgColor=3D#2f4f4f border=3D0>
  <TBODY>
  <TR>
    <TD><PRE class=3DSCREEN><FONT color=3D#f5deb3 size=3D+1><FONT =
color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT =
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