perl - 如何在“闭包范围”内执行 lambda？

Question

这怎么行？

    use strict;
    use warnings;

    sub base {
      my $constant = "abcd";
      my ($driver_cr) = (@_);
      &$driver_cr;
    }

    base(sub {print $constant});

换句话说，$driver_cr 如何在没有以下条件的情况下访问 $constant：

1. 将 $constant 作为 arg 传递给驱动程序 &$driver_cr($constant)
2. 将 $constant 的范围更改为全局our $constant = "abcd";

3. 制作一个公共块并从基础移动 $constant：

   use strict;
   use warnings;
   
   {
     my $constant = "abcd";
     sub base {
       my ($driver_cr) = (@_);
       &$driver_cr;
     }
     base(sub {print $constant});
   }
   

Answer 1

这就是函数参数的用途。

use strict;
use warnings;

sub base {
  my $constant = "abcd";
  my ($driver_cr) = (@_);
  $driver_cr->($constant);
}

base(sub {
    my $constant = shift;
    print $constant;
});

但如果你真的反对传递参数，那么：

use strict;
use warnings;
use Acme::Lexical::Thief;

sub base {
  my $constant = "abcd";
  my ($driver_cr) = (@_);
  &$driver_cr;
}

base(sub {
    steal $constant;
    print $constant;
});