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<p align="center">第四章 列表和數(shù)組變量</p>
<p align="center"><a target="_blank" href="http://flamephoenix.126.com">by flamephoenix</a></p>
<a href="#一、列表">一、列表</a><br>
<a href="#二、數(shù)組--列表的存貯">二、數(shù)組--列表的存貯</a><br>
<a href="#1、數(shù)組的存取">1、數(shù)組的存取</a><br>
<a href="#2、字符串中的方括號(hào)和變量替換">2、字符串中的方括號(hào)和變量替換</a> <br>
<a href="#3、列表范圍：">3、列表范圍</a><br>
<a href="#4、數(shù)組的輸出：">4、數(shù)組的輸出</a><br>
<a href="#5、列表/數(shù)組的長(zhǎng)度">5、列表/數(shù)組的長(zhǎng)度</a><br>
<a href="#6、子數(shù)組">6、子數(shù)組</a><br>
<a href="#7、有關(guān)數(shù)組的庫(kù)函數(shù)">7、有關(guān)數(shù)組的庫(kù)函數(shù)</a>
<br><br>
<a name="一、列表">一、列表</a><br>
列表是包含在括號(hào)里的一序列的值，可以為任何數(shù)值，也可為空，如：(1,
5.3 , "hello" , 2)，空列表：()。<br>
注：只含有一個(gè)數(shù)值的列表(如：(43.2) )與該數(shù)值本身(即：43.2
)是不同的，但它們可以互相轉(zhuǎn)化或賦值。<br>
列表例：<br>
(17, $var, "a string")<br>
(17, 26 << 2)<br>
(17, $var1 + $var2)<br>
($value, "The answer is
$value")<br>
<a name="二、數(shù)組--列表的存貯">
二、數(shù)組--列表的存貯</a>
<br>
列表存貯于數(shù)組變量中，與簡(jiǎn)單變量不同，數(shù)組變量以字符"@"打頭，如：<br>
@array = (1, 2, 3);<br>
注：<br>
(1)數(shù)組變量創(chuàng)建時(shí)初始值為空列表：()。<br>
(2)因?yàn)镻ERL用@和$來(lái)區(qū)分?jǐn)?shù)組變量和簡(jiǎn)單變量，所以同一個(gè)名字可以同時(shí)用于數(shù)組變量和簡(jiǎn)單變量，如：<br>
$var = 1;<br>
@var = (11, 27.1 , "a string");<br>
但這樣很容易混淆，故不推薦。<br>
<a name="1、數(shù)組的存取">1、數(shù)組的存取</a>
<br>
.對(duì)數(shù)組中的值通過(guò)下標(biāo)存取，第一個(gè)元素下標(biāo)為0。試圖訪問(wèn)不存在的數(shù)組元素，則結(jié)果為NULL，但如果給超出數(shù)組大小的元素賦值，則數(shù)組自動(dòng)增長(zhǎng)，原來(lái)沒(méi)有的元素值為NULL。如：<br>
@array = (1, 2, 3, 4);<br>
$scalar = $array[0];<br>
$array[3] = 5; # now @array is (1,2,3,5)<br>
$scalar = $array[4]; # now $scalar =
null;<br>
$array[6] = 17; # now @array is
(1,2,3,5,"","",17)<br>
.數(shù)組間拷貝<br>
@result = @original; <br>
.用數(shù)組給列表賦值<br>
@list1 = (2, 3, 4);<br>
@list2 = (1, @list1, 5); # @list2 = (1,
2, 3, 4, 5)<br>
.數(shù)組對(duì)簡(jiǎn)單變量的賦值<br>
(1) @array = (5, 7, 11);<br>
($var1, $var2) = @array; # $var1 = 5,
$var2 = 7, 11被忽略<br>
(2) @array = (5, 7);<br>
($var1, $var2, $var3) = @array; # $var1 =
5, $var2 = 7, $var3 ="" (null)<br>
.從標(biāo)準(zhǔn)輸入(STDIN)給變量賦值<br>
$var = <STDIN>;<br>
@array = <STDIN>; # ^D為結(jié)束輸入的符號(hào)<br>
<a name="2、字符串中的方括號(hào)和變量替換">
2
、字符串中的方括號(hào)和變量替換
</a> <br>
"$var[0]" 為數(shù)組@var的第一個(gè)元素。<br>
"$var\[0]" 將字符"["轉(zhuǎn)義，等價(jià)于"$var".
"[0]"，$var被變量替換，[0]保持不變。<br>
"${var}[0]" 亦等價(jià)于"$var"
."[0]"。<br>
"$\{var}"則取消了大括號(hào)的變量替換功能，包含文字：${var}.<br>
<a name="3、列表范圍：">
3、列表范圍：</a>
<br>
(1..10) = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10)<br>
(2, 5..7, 11) = (2, 5, 6, 7, 11)<br>
(3..3) = (3)<br>
.用于實(shí)數(shù)<br>
(2.1..5.3) = (2.1, 3.1 ,4.1, 5.1)<br>
(4.5..1.6) = ()<br>
.用于字符串<br>
("aaa".."aad") =
("aaa","aab", "aac",
"aad")<br>
@day_of_month =
("01".."31")<br>
.可包含變量或表達(dá)式<br>
($var1..$var2+5)<br>
.小技巧：<br>
$fred = "Fred";<br>
print (("Hello, " . $fred .
"!\n") x 2); <br>
其結(jié)果為：<br>
Hello, Fred!<br>
Hello, Fred! <br>
<a name="4、數(shù)組的輸出：">
4、數(shù)組的輸出：</a>
<br>
(1) @array = (1, 2, 3);<br>
print (@array, "\n");<br>
結(jié)果為：<br>
123<br>
(2) @array = (1, 2, 3);<br>
print ("@array\n");<br>
結(jié)果為：<br>
1 2 3<br>
<a name="5、列表/數(shù)組的長(zhǎng)度">5、列表/數(shù)組的長(zhǎng)度</a>
<br>
當(dāng)數(shù)組變量出現(xiàn)在預(yù)期簡(jiǎn)單變量出現(xiàn)的地方，則PERL解釋器取其長(zhǎng)度。<br>
@array = (1, 2, 3);<br>
$scalar = @array; # $scalar = 3,即@array的長(zhǎng)度<br>
($scalar) = @array; # $scalar = 1,即@array第一個(gè)元素的值<br>
注：以數(shù)組的長(zhǎng)度為循環(huán)次數(shù)可如下編程：<br>
$count = 1;<br>
while ($count <= @array) {<br>
print ("element $count:
$array[$count-1]\n");<br>
$count++;<br>
}<br>
<a name="6、子數(shù)組">6、子數(shù)組</a>
<br>
@array = (1, 2, 3, 4, 5);<br>
@subarray = @array[0,1]; # @subarray =
(1, 2)<br>
@subarray2 = @array[1..3]; # @subarray2 =
(2,3,4)<br>
@array[0,1] = ("string", 46); #
@array =("string",46,3,4,5) now <br>
@array[0..3] = (11, 22, 33, 44); # @array
= (11,22,33,44,5) now<br>
@array[1,2,3] = @array[3,2,4]; # @array =
(11,44,33,5,5) now<br>
@array[0..2] = @array[3,4]; # @array =
(5,5,"",5,5) now<br>
可以用子數(shù)組形式來(lái)交換元素：<br>
@array[1,2] = @array[2,1];<br>
<a name="7、有關(guān)數(shù)組的庫(kù)函數(shù)">
7、有關(guān)數(shù)組的庫(kù)函數(shù)</a>
<br>
(1)sort--按字符順序排序<br>
@array = ("this",
"is", "a","test");<br>
@array2 = sort(@array); # @array2 =
("a","is", "test",
"this")<br>
@array = (70, 100, 8);<br>
@array = sort(@array); # @array = (100,
70, 8) now<br>
(
2)reverse--反轉(zhuǎn)數(shù)組<br>
@array2 = reverse(@array);<br>
@array2 = reverse sort (@array);<br>
(3)chop--數(shù)組去尾<br>
chop的意義是去掉STDIN（鍵盤(pán)）輸入字符串時(shí)最后一個(gè)字符--換行符。而如果它作用到數(shù)組上，則將數(shù)組中每一個(gè)元素都做如此處理。<br>
@list = ("rabbit",
"12345","quartz");<br>
chop (@list); # @list =
("rabbi", "1234","quart") now<br>
(
4)join/split--連接/拆分<br>
join的第一個(gè)參數(shù)是連接所用的中間字符，其余則為待連接的字符數(shù)組。<br>
$string = join(" ",
"this", "is","a",
"string"); # 結(jié)果為"this is a string"<br>
@list =
("words","and");<br>
$string = join("::", @list,
"colons"); #結(jié)果為"words::and::colons"<br>
@array = split(/::/,$string); # @array =
("words","and", "colons") now<br>
</p>
<p align="center"><a href="perl3.htm">上一章</a> <a href="perl5.htm">下一章</a> <a href="index.htm">目錄</a></p>
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