我可能患有大脑衰退，但根据有关项目和列表分配的文档（https://docs.raku.org/language/variables#Item_and_list_assignment https://docs.raku.org/language/variables#Item_and_list_assignment ),

对列表容器（列表上下文）的分配始终会触发列表分配。

然而，这似乎与我从代码中得到的内容相冲突（此处在 raku repl 中复制）。

> my %syns-by-name = %(Bq => ["Bq", "becquerel", "becquerels"], C => ["C", "coulomb", "coulombs"],)
    {Bq => [Bq becquerel becquerels], C => [C coulomb coulombs]}
> my Str @res = %syns-by-name{'Bq'};
    Type check failed in assignment to @res; expected Str but got Array (["Bq", "becquerel", ...) in block <unit> at <unknown file> line 1
> my Str @res = [|%syns-by-name{'Bq'}];
    [Bq becquerel becquerels]

这是一个错误，还是我误解了意图......？

Welcome to ????????????????????????™ v2020.10.
Implementing the ????????????????™ programming language v6.d.
Built on MoarVM version 2020.10.

TL;DR If a non-native item is mutable via assignment, it's a Scalar. List assignment does not flatten Scalar items. ^[1]

一个暗示

考虑这段代码：

my %map = :a;
%map<a> = 42;
say %map<a>; # 42

该作业之所以有效，是因为：

say %map<a>.VAR.WHAT; # (Scalar)

“列表分配”

考虑这段代码：

my $scalar = 1,2;       # Useless use of constant integer 2
say $scalar;            # 1

my @list1 = 1,2;        # "list assignment", so RHS is iterated
say @list1;             # [1 2]

这就是项目分配和列表分配之间的区别之一。

my @list3 = [1,2];      # Again, RHS is iterated
say @list3;             # [1 2]

my @list2 = (1,2);      # Again, RHS is iterated
say @list2;             # [1 2]

my @list4 = 1,(2,3);    # Again, RHS is iterated. Second element stays as a `List`.
say @list4;             # [1 (2 3)]

my @list5 = 1,[2,3];    # Again, RHS is iterated. Second element stays as an `Array`.
say @list5;             # [1 [2 3]]

如果 RHS 上只列出了一项，这不是一个Scalar，列表分配将其展平。但在所有其他情况下，列表分配不会展平项目。

my @list6 = $[1,2];     # RHS is a `Scalar`. So it doesn't get flattened.
say @list6;             # [[1 2]]

我很困惑！

高尔夫Q中的情况：

my Str @res = %( :a[42,99] )<a>;

这会产生同样类型的错误。

Because:

say .VAR.WHAT given :a[42,99]<a>;       # (Array)
say .VAR.WHAT given (% = :a[42,99])<a>; # (Scalar)

脚注

^[1] When surmise yields surprise, and you turn that into learning, you realize and idealize your investment in ERN https://en.wikipedia.org/wiki/Error-related_negativitying.