Perl 6中有哪些重要空间？

Question

Perl 6清除了其前身中的一些奇怪情况，它不允许在某些位置使用空格，但也允许在其他位置执行作业。空间在哪里重要？如果有一个完整的参考资料就好了，因此我添加了一个社区维基答案，我会用你的代表收入答案更新。感谢您的示例！

但是，还要记住Perl 6有unspace，因此可以使用\使空白有效地不可见。例如，不应显示子例程名称及其参数列表，但使用unspace可以：

sub-name    ( @arguments );  # not okay
sub-name\   ( @arguments );  # okay

Answer 1

为什么这个Perl 6提要操作符是“伪语句”？我有一个例子，其中grep的}将作为语句的结尾，因为隐含的分号：

my @rakudo-people = <scott patrick carl moritz jonathan jerry stephen>;
@rakudo-people
    ==> grep { /at/ } \
    ==> map { .uc } ==> my @who-it's-at;
say ~@who-it's-at;

我忘了我在哪里找到这个例子

my @a = [[<foo>],]; # Is that a reduction?

my @a = [[ <foo>],]; # That space certainly means it's not one?

$hash <key>; # Error, indexing uses postfix operators
$hash<key>; # Works

call-this-subroutine    ( @arguments );  # Error
call-this-subroutine( @arguments ); # Works

my $x = 5;
say $x ++;  # Error
say $x++;   # Works

这对于前缀运算符不是问题：

my $x = 5;
say ++ $x;  # Works
say ++$x;   # Works

Answer 2

结束模式的位置（此处为结束）决定了此heredoc中的重要空间：

my $letter = q:to/END/;
    Foo, bar, baz
      <- The preceding two spaces are included in the heredoc.
    END

put $letter;

当run为我们提供：

Foo, bar, baz
  <- The preceding two spaces are included in the heredoc.

尽可能不缩进结尾，会导致heredoc中出现更多的空白：

my $letter = q:to/END/;
    Foo, bar, baz
      <- The preceding four spaces are included in the heredoc.
  END

put $letter;

  Foo, bar, baz
    <- The preceding four spaces are included in the heredoc.

my $greeting = " Hello World! ";
my $salutation = "Hello World!";

put $greeting;
put $salutation;

 Hello World!
Hello World!

下面的例子来自https://docs.perl6.org/language/quoting#Literal_strings：_Q。

Q'this will not work!'
Q(this won't work either!)
Q (this is fine, because of space after Q)
Q 'and so is this'

但是其他分隔符可以使用或不使用空格：

Q^This works!^
Q ^so does this^

Answer 3

> my %a = (A=>1, B=>2, C=>3);
{A => 1, B => 2, C => 3}
> %a<A>;
1
> %a <A>;
===SORRY!=== Error while compiling:
Missing required term after infix
------> %a <A>⏏;
    expecting any of:
        prefix
        term
> %a\ <A>;
1

同样，插值被空格打破，我不知道在插值环境中使用unspace的方法。但是当使用{}插值代码的结果时，您可以在打开{之后引入空格：

> put "%a<A>";
1
> put "%a <A>";
%a <A>
> put "%a\ <A>";
%a <A>
> put "%a {'A'}"
%a A
> put "%a{<A>}"
1
> put "%a{ <A> }"
1

此循环适用于Perl 5，但不适用于Perl 6：

for (1,2,3){
    print "counting $_!\n";
}

===SORRY!=== Error while compiling testing.p6
Missing block (whitespace needed before curlies taken as a hash subscript?)
at testing.p6:4
------> <BOL>⏏<EOL>
    expecting any of:
        block or pointy block

但最后括号后面的空格纠正了这一点：

for (1,2,3) {
    print "counting $_!\n";
}

counting 1!
counting 2!
counting 3!

这曾经一直困扰着我，直到我了解到控制流构造的条件通常不需要括号（例如for、while和if构造）。

为了避免这种情况，只需省略括号：

for 1,2,3 {
    print "counting $_!\n";
}

但你仍然必须在大括号前留出空间：

for 1,2,3{
    print "counting $_!\n";
}

===SORRY!=== Error while compiling testing.p6
Missing block (whitespace needed before curlies taken as a hash subscript?)
at testing.p6:4
------> <BOL>⏏<EOL>
    expecting any of:
        block or pointy block