子例程中的默认参数值 [英] Default argument values in subroutines

问题描述

我现在已经和Perl一起工作了两个月了。我发现我不知道如何为子例程设置默认参数。这是我考虑的：

  sub hello {
 print @_ || 你好，世界; 
} 
  

如果你需要的只是一个参数，你将如何为多个参数设置默认值？我打算这样做：

  sub hello {
 my $ say = $ _ [0] || 你好; 
 my $ to = $ _ [1] || 世界！; 
打印$ say $ to; 
} 
  

但是这需要很多工作......必须有一个更简单的方法;可能是最佳做法？感谢！

解决方案

我使用如下所示的命名参数完成它：

  sub hello {
 my（％arg）=（
'foo'=>'default_foo'，
'bar'=>'default_bar '，
 @_ 
）; 
 
} 
  

我相信 Params :: Validate 支持默认值，但这比我喜欢的要麻烦。

I have been working with perl for about two months now; it just occurred to me that I don't know how to set default arguments for subroutines. Here is what I considered:

sub hello {
  print @_ || "Hello world";
}

And that works fine for if all you needed was one argument. How would you set default values for multiple arguments? I was going to do this:

sub hello {
  my $say = $_[0] || "Hello";
  my $to  = $_[1] || "World!";
  print "$say $to";
}

But that's a lot of work... There must be an easier way; possibly a best practice? Thanks!

解决方案

I do it with named arguments like so:

sub hello {
    my (%arg) = (
        'foo' => 'default_foo',
        'bar' => 'default_bar',
        @_
    );

}

I believe Params::Validate supports default values, but that's more trouble than I like to take.

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