五、多維數組 語句@array = list;可以創建數組的引用,中括號可以創建匿名數組的引用。下面語句為用于畫圖的三維數組的例子: $line = ['solid' , 'black' , ['1','2','3'] , ['4','5','6']]; 此語句建立了一個含四個元素的三維數組,變量$line指向該數組。前兩個元素是標量,存貯線條的類型和顏色,后兩個元素是匿名數組的引用,存貯線條的起點和終點。訪問其元素語法如下:
$arrayReference->[$index] single-dimensional array $arrayReference->[$index1][$index2] two-dimensional array $arrayReference->[$index1][$index2][$index3] three-dimensional array 可以創建在你的智力、設計經驗和計算機的內存允許的情況下極盡復雜的結構,但最好對可能讀到或管理你的代碼的人友好一些--盡量使代碼簡單些。另一方面,如果你想向別人炫耀你的編程能力,Perl給你足夠的機會和能力編寫連自己都難免糊涂的代碼。:) 建議:當你想使用多于三維的數組時,最好考慮使用其它數據結構來簡化代碼。 下面為創建和使用二維數組的例子:
1 #!/usr/bin/perl 2 # 3 # Using Multi-dimensional Array references 4 # 5 $line = ['solid', 'black', ['1','2','3'] , ['4', '5', '6']]; 6 print "\$line->[0] = $line->[0] \n"; 7 print "\$line->[1] = $line->[1] \n"; 8 print "\$line->[2][0] = $line->[2][0] \n"; 9 print "\$line->[2][1] = $line->[2][1] \n"; 10 print "\$line->[2][2] = $line->[2][2] \n"; 11 print "\$line->[3][0] = $line->[3][0] \n"; 12 print "\$line->[3][1] = $line->[3][1] \n"; 13 print "\$ine->[3][2] = $line->[3][2] \n"; 14 print "\n"; # The obligatory output beautifier. 結果輸出如下:
$line->[0] = solid $line->[1] = black $line->[2][0] = 1 $line->[2][1] = 2 $line->[2][2] = 3 $line->[3][0] = 4 $line->[3][1] = 5 $line->[3][2] = 6 那么三維數組又如何呢?下面是上例略為改動的版本。
1 #!/usr/bin/perl 2 # 3 # Using Multi-dimensional Array references again 4 # 5 $line = ['solid', 'black', ['1','2','3', ['4', '5', '6']]]; 6 print "\$line->[0] = $line->[0] \n"; 7 print "\$line->[1] = $line->[1] \n"; 8 print "\$line->[2][0] = $line->[2][0] \n"; 9 print "\$line->[2][1] = $line->[2][1] \n"; 10 print "\$line->[2][2] = $line->[2][2] \n"; 11 print "\$line->[2][3][0] = $line->[2][3][0] \n"; 12 print "\$line->[2][3][1] = $line->[2][3][1] \n"; 13 print "\$line->[2][3][2] = $line->[2][3][2] \n"; 14 print "\n"; 結果輸出如下:
$line->[0] = solid $line->[1] = black $line->[2][0] = 1 $line->[2][1] = 2 $line->[2][2] = 3 $line->[2][3][0] = 4 $line->[2][3][1] = 5 $line->[2][3][2] = 6 訪問第三層元素的方式形如$line->[2][3][0],類似于C語言中的Array_pointer[2][3][0]。本例中,下標均為數字,當然亦可用變量代替。用這種方法可以把數組和哈希表結合起來構成復雜的結構,如下:
1 #!/usr/bin/perl 2 # 3 # Using Multi-dimensional Array and Hash references 4 # 5 %cube = ( 6 '0', ['0', '0', '0'], 7 '1', ['0', '0', '1'], 8 '2', ['0', '1', '0'], 9 '3', ['0', '1', '1'], 10 '4', ['1', '0', '0'], 11 '5', ['1', '0', '1'], 12 '6', ['1', '1', '0'], 13 '7', ['1', '1', '1'] 14 ); 15 $pointer = \%cube; 16 print "\n Da Cube \n"; 17 foreach $i (sort keys %$pointer) { 18 $list = $$pointer{$i}; 19 $x = $list->[0]; 20 $y = $list->[1]; 21 $z = $list->[2]; 22 printf " Point $i = $x,$y,$z \n"; 23 } 結果輸出如下:
Da Cube Point 0 = 0,0,0 Point 1 = 0,0,1 Point 2 = 0,1,0 Point 3 = 0,1,1 Point 4 = 1,0,0 Point 5 = 1,0,1 Point 6 = 1,1,0 Point 7 = 1,1,1 這是一個定義立方體的例子。%cube中保存的是點號和坐標,坐標是個含三個數字的數組。變量$list獲取坐標數組的引用:$list = $$ pointer{$i}; 然后訪問各坐標值:$x = $list->[0]; ... 也可用如下方法給$x、$y和$z賦值:($x,$y,$z) = @$list; 使用哈希表和數組時,用$和用->是類似的,對數組而言下面兩個語句等效: $$names[0] = "kamran"; $names->[0] = "kamran"; 對哈希表而言下面兩個語句等效: $$lastnames{"kamran"} = "Husain"; $lastnames->{"kamran"} = "Husain"; Perl中的數組可以在運行中創建和擴展。當數組的引用第一次在等式左邊出現時,該數組自動被創建,簡單變量和多維數組也是一樣。如下句,如果數組contours不存在,則被創建: $contours[$x][$y][$z] = &xlate($mouseX, $mouseY);
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