在 Perl 6 中将正则表达式作为参数传递 [英] Passing regexes as arguments in Perl 6

问题描述

这个问题的延续，可能还有一个更奇怪的问题.

A continuation of this question, and probably an even more weird one.

我可以例如使用 sub 连接两个 regex?(当然，我明白，如何用 regex 做到这一点)

Can I e.g. concatenate two regexes using a sub? (Of course, I understand, how to do it with a regex)

下面的代码是完全错误的，但我希望它能解释我想做什么:

The following code is totally wrong, but I hope it can explain what I want to do:

my Regex sub s12 ( $c, $v) {
   return / <{$c}> <{$v}> /
}

my regex consonant { <[a .. z] -[aeiou]>  }
my regex vowel { <[aeiou]> }

my regex open_syllable { &s12( &consonant, &vowel ) }

"bac" ~~ m:g/ <open_syllable> /;
say $/; # should be 'ba'

推荐答案

你写的基本上是对的，但你需要稍微调整一下语法.首先，您应该像任何其他子程序一样声明您的组合函数.接下来，似乎将一个正则表达式插入另一个，<$r> 是正确的语法，并将函数调用插入到一个正则表达式中，<{my-sub(args)}> 是正确的语法.(调用时不需要在 sub 前面加上 & 号——& 主要用于当你想引用 Callable 而不调用它时.)结合这些小修复并且您的代码有效:

What you wrote is basically right, but you need to tweak the syntax a little. First, you should declare your combining function like any other sub. Next, it seems like to interpolate a regex into another, <$r> is the right syntax, and to interpolate a function call into a regex, <{my-sub(args)}> is the right syntax. (No need to prefix the sub with an ampersand when calling it—& is mostly for when you want to refer to a Callable without calling it.) Combine these little fixes and your code works:

sub combine(Regex $a, Regex $b --> Regex) {
    / <$a> <$b> /
}

my regex consonant { <[a .. z] -[aeiou]>  }
my regex vowel { <[aeiou]> }

my regex open_syllable { <{combine(&consonant, &vowel)}> }

"bac" ~~ m:g/ <open_syllable> /;
say ~$/; # output: ba

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