Question

我继承了以下形式的函数：

sub func($$) {

}

我更习惯看到：

sub func {
  ## then extract params using shift for example
}

我查了$$，这是获取当前进程ID的一种方法。但是看看这个函数看起来并不像这里使用的是进程ID。那么$$在这种情况下是什么意思呢？

我困惑的功能是下面的parseMessage。为什么($$)？

use FileHandle;

# The structure of function is pretty much like this - names changed only
sub parseMessage($$)
{
  my $string = shift;
  my $fileHandle = shift;

  my $Message = undef;

  # parseAMessage and parseBMessage are functions to extract specific types of messages from file
  if ( ($Message = parseAMessage($string, $fileHandle))
    || ($Message = parseBMessage($string, $fileHandle)) )
  {

  }

  return $Message;
}


sub parseAMessage($$)
{
}

sub parseBMessage($$)
{
}

# The function seems to use arguments arg1: string from file, arg2: filehandle of file
# presumably idea behind this is to process current line in file but also have access to file
# handle to move to next line where required. So the way I am calling this is probably not
# great Perl - I am a beginner perler
$fh = FileHandle->new;
    if ($fh->open("< myfile.log")) {
        # here we evaluate the file handle in a scalar context to get next line
        while($line = <$fh>) {
            parseMessage($line, $fh);   
            #print <$fh>;
        }

        $fh->close;
    }
    print "DONE\n";
1;

Answer 1

它们是原型并定义函数作为参数的内容（不安全..）。

它允许您定义内置函数之类的函数，因此您可以像调用sub doSomething一样调用print。

doSomething($scalar)或doSomething $scalar会产生相同的结果，例如print($scalar)与print $scalar

根据上述评论：http://perldoc.perl.org/perlsub.html#Prototypes

Perl函数（$$）形式有什么特别之处？

1 个答案: