我应该调用没有参数的 Perl 子程序作为海洋()还是海洋? [英] Should I call Perl subroutines with no arguments as marine() or marine?

问题描述

根据我下面的示例代码，调用子程序有两种样式:subname 和 subname().

As per my sample code below, there are two styles to call a subroutine: subname and subname().

#!C:\Perl\bin\perl.exe
use strict;
use warnings;

use 5.010;

&marine(); # style 1
&marine; # style 2

sub marine {
    state $n = 0; # private, persistent variable $n
    $n += 1;
    print "Hello, sailor number $n!\n";
}

如果调用中没有参数，&marine(); 或 &marine; 哪个是更好的选择?

Which one, &marine(); or &marine;, is the better choice if there are no arguments in the call?

推荐答案

在学习 Perl，这个例子来自哪里，我们刚开始向您展示子程序.我们只告诉您使用 & 以便您，作为开始的 Perler，不会遇到定义与 Perl 内置同名的子例程的问题，然后想知道为什么它不起作用.前面的 & 总是调用你定义的子程序.初学者经常创建他们自己的子程序 log 来打印消息，因为他们习惯于在他们使用的其他技术中这样做.在 Perl 中，这是内置的数学函数.

In Learning Perl, where this example comes from, we're at the very beginning of showing you subroutines. We only tell you to use the & so that you, as the beginning Perler, don't run into a problem where you define a subroutine with the same name as a Perl built-in then wonder why it doesn't work. The & in front always calls your defined subroutine. Beginning students often create their own subroutine log to print a message because they are used to doing that in other technologies they use. In Perl, that's the math function builtin.

在您习惯使用 Perl 并了解 Perl 内置程序后(浏览 perlfunc)，删除 &.& 有一些你几乎不需要的特殊魔法:

After you get used to using Perl and you know about the Perl built-ins (scan through perlfunc), drop the &. There's some special magic with & that you hardly ever need:

 marine();

如果您预先声明了子例程，您可以省略 ()，但我通常将 () 留在那里，即使是空参数列表也是如此.由于您向 Perl 提示 marine 是一个子例程名称，因此它更健壮一些.对我来说，我更快地认识到这是一个子程序.

You can leave off the () if you've pre-declared the subroutine, but I normally leave the () there even for an empty argument list. It's a bit more robust since you're giving Perl the hint that the marine is a subroutine name. To me, I recognize that more quickly as a subroutine.

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