数组程式求解释(已解决！）感谢论坛牛人pitonas ！

求浩871227

来自论坛牛人pitonas的当时帮助提供的程式：
while (<DATA>) {
    my @a = map split, $_, ~~<DATA>, ~~<DATA>;
    say "@a[ 0, 2 ]";
    say "@a[ 4, 1 ]";
    say "@a[ 3, 5 ]";
}

__DATA__
1 4
2 5
3 6
7 10
8 11
9 12
13 16
14 17
15 18
19 22
20 23
21 24
25 28
26 29
27 30

“my @a = map split, $_, ~~<DATA>, ~~<DATA>;”
pitonas再次细心解答（太感谢！！！）：

# in scalar context:

my $a = <DATA>;    # read only one line

# in list context:

my @a = scalar <DATA>;    # read only one line
my @b = ~~ <DATA>;          # read only one line
my @c = <DATA>;           # read all lines


my @a = map { ... } ...   # list context

# 这些相同。

my @a = map split, $_, ~~<DATA>, ~~<DATA>;
my @a = map { split } $_, ~~<DATA>, ~~<DATA>;
my @a = map { split } $_, scalar <DATA>, scalar <DATA>;
my @a = map { split /\s+/ } $_, scalar <DATA>, scalar <DATA>;
my @a = map { split /\s+/, $_ } $_, scalar <DATA>, scalar <DATA>;

pitonas

这个有很多种写法 ~ {:2_179:}

1: 幼儿园风格的代码 ( 包含无用的操作 )

1. #!/usr/bin/perl
   
2. 
   
3. my $TRUE = 1;
   
4. 
   
5. while ($TRUE) {
   
6. 
   
7.     my $line1 = readline DATA;
   
8.     my $line2 = readline DATA;
   
9.     my $line3 = readline DATA;
   
10. 
    
11.     chomp $line1;
    
12.     chomp $line2;
    
13.     chomp $line3;
    
14. 
    
15.     my @lines1 = split /\s/, $line1;
    
16.     my @lines2 = split /\s/, $line2;
    
17.     my @lines3 = split /\s/, $line3;
    
18. 
    
19.     my @three_lines = ();
    
20.     my $index       = 0;
    
21. 
    
22.     for ( my $i = 0 ; $i < @lines1 ; $i++ ) {
    
23.         $three_lines[$index] = $lines1[$i];
    
24.         $index = $index + 1;
    
25.     }
    
26. 
    
27.     for ( my $i = 0 ; $i < @lines2 ; $i++ ) {
    
28.         $three_lines[$index] = $lines2[$i];
    
29.         $index = $index + 1;
    
30.     }
    
31. 
    
32.     for ( my $i = 0 ; $i < @lines3 ; $i++ ) {
    
33.         $three_lines[$index] = $lines3[$i];
    
34.         $index = $index + 1;
    
35.     }
    
36. 
    
37.     print $three_lines[0];
    
38.     print ' ';
    
39.     print $three_lines[2];
    
40.     print "\n";
    
41.     print $three_lines[4];
    
42.     print ' ';
    
43.     print $three_lines[1];
    
44.     print "\n";
    
45.     print $three_lines[3];
    
46.     print ' ';
    
47.     print $three_lines[5];
    
48.     print "\n";
    
49. 
    
50.     $TRUE = 0 if eof;
    
51. 
    
52. }
    
53. 
    
54. __DATA__
    
55. 1 4
    
56. 2 5
    
57. 3 6
    
58. 7 10
    
59. 8 11
    
60. 9 12
    
61. 13 16
    
62. 14 17
    
63. 15 18

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2: 简约低调有内涵的代码

1. #!/usr/bin/perl
   
2. 
   
3. until (eof) {
   
4.     my @a = split /\s/, <DATA> . <DATA> . <DATA>;
   
5.     print map "@a[@$_]\n", [ 0, 2 ], [ 4, 1 ], [ 3, 5 ];
   
6. }
   
7. 
   
8. __DATA__
   
9. 1 4
   
10. 2 5
    
11. 3 6
    
12. 7 10
    
13. 8 11
    
14. 9 12
    
15. 13 16
    
16. 14 17
    
17. 15 18

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1. #!/usr/bin/perl
   
2. 
   
3. until (eof) {
   
4.     my @a = map split, ~~ <DATA>, ~~ <DATA>, ~~ <DATA>;
   
5.     print "@a[@$_]\n" for [ 0, 2 ], [ 4, 1 ], [ 3, 5 ];
   
6. }
   
7. 
   
8. __DATA__
   
9. 1 4
   
10. 2 5
    
11. 3 6
    
12. 7 10
    
13. 8 11
    
14. 9 12
    
15. 13 16
    
16. 14 17
    
17. 15 18

复制代码