@{}是什么啊？菜鸟求助

64805176

#!/usr/bin/perl

my %h;
while (<DATA>) {
    my ( $i, $j ) = split;
    push @{ $h{$i} }, $j;
}

__DATA__
a        b
a        c
b        e
b        f
c        e
c        f
b        c
e        f



  push @{ $h{$i} }, $j;这一句是什么意思啊？

sjdy521

简单的说就是解引用(dereference)

参见http://perldoc.perl.org/perlref.html

Using a reference as a string produces both its referent's type, including any package blessing as described in perlobj, as well as the numeric address expressed in hex. The ref() operator returns just the type of thing the reference is pointing to, without the address. See ref for details and examples of its use.

The bless() operator may be used to associate the object a reference points to with a package functioning as an object class. See perlobj.

A typeglob may be dereferenced the same way a reference can, because the dereference syntax always indicates the type of reference desired. So ${*foo} and ${\$foo} both indicate the same scalar variable.

Here's a trick for interpolating a subroutine call into a string:
    print "My sub returned @{[mysub(1,2,3)]} that time.\n";

The way it works is that when the @{...} is seen in the double-quoted string, it's evaluated as a block. The block creates a reference to an anonymous array containing the results of the call to mysub(1,2,3) . So the whole block returns a reference to an array, which is then dereferenced by @{...} and stuck into the double-quoted string. This chicanery is also useful for arbitrary expressions:
    print "That yields @{[$n + 5]} widgets\n";

Similarly, an expression that returns a reference to a scalar can be dereferenced via ${...} . Thus, the above expression may be written as:
    print "That yields ${\($n + 5)} widgets\n";

兰花仙子

64805176 发表于 2012-04-17 17:36
#!/usr/bin/perl

my %h;

$h{$i}指向一个匿名数组。
@{ $h{$i} } 就是解引用这个数组，因为要往里面push东西。

pengphy

回复 1# 64805176


    你可以百度或者google一下 hash autovivification， perl intermediate 推荐你读一下前6章

wonderall01

兰花仙子 发表于 2012-04-17 20:57
$h{$i}指向一个匿名数组。
@{ $h{$i} } 就是解引用这个数组，因为要往里面push东西。

怎么print %h后是一串地址呢？不应该是将DATA数据当做hash存放在%h中的吗？

pengphy

回复 5# wonderall01


    你用Data:umper去Dump一下整个数据结构 看看里面到底是一个什么玩意儿

wonderall01

pengphy 发表于 2012-04-18 11:08
回复 5# wonderall01

dump出来数据时对的，但是直接打印哈希%h就输出的键正确但是值却是地址呢？

pengphy

回复 7# wonderall01


    perl intermediate chapter4&5, 你应该先看一下这两章内容 之后还是不明白再问吧

wonderall01

pengphy 发表于 2012-04-18 12:36
回复 7# wonderall01

好滴。

64805176

回复 3# 兰花仙子


   我还是不太明白这里$h{$i}
比如说读取第一行 a   b
$i=a, $h{$i}应该是$h{a}，$h{a}应该就是b啊，为什么是一个地址呢

怎么理解呢？？