perl6/rakudo:无法解析postcircumfix:sym <()>

Question

为什么我收到此错误消息？

#!perl6
use v6;

my @a = 1..3;
my @b = 7..10;
my @c = 'a'..'d';


for zip(@a;@b;@c) -> $nth_a, $nth_b, $nth_c { ... };


# Output:

# ===SORRY!===
# Unable to parse postcircumfix:sym<( )>, couldn't find final ')' at line 9

Answer 1

Rakudo 尚未实现 lol（“列表的列表”）形式，因此无法解析@a;@b;@c. 出于同样的原因，zip还没有包含三个列表的表单。显然，错误消息不太好。

目前还没有真正好的解决方法，但这里有一些可以完成工作的方法：

sub zip3(@a, @b, @c) {
    my $a-list = flat(@a.list);
    my $b-list = flat(@b.list);
    my $c-list = flat(@c.list);
    my ($a, $b, $c);
    gather while ?$a-list && ?$b-list && ?$c-list {
        $a = $a-list.shift unless $a-list[0] ~~ ::Whatever;
        $b = $b-list.shift unless $b-list[0] ~~ ::Whatever;
        $c = $c-list.shift unless $c-list[0] ~~ ::Whatever;
        take ($a, $b, $c);
    }
}

for zip3(@a,@b,@c) -> $nth_a, $nth_b, $nth_c {
    say $nth_a ~ $nth_b ~ $nth_c;
}