小编dfh*_*ton的帖子

我有一个包，我想添加一个可选功能。我已在 Cargo.toml 中添加了适当的部分：

[features]
foo = []

我为宏的基本功能编写了一个实验测试cfg!：

#[test]
fn testing_with_foo() {
    assert!(cfg!(foo));
}

看起来我可以在测试期间通过以下选项之一激活功能--features：--all-features

(master *=) $ cargo help test
cargo-test 
Execute all unit and integration tests and build examples of a local package

USAGE:
    cargo test [OPTIONS] [TESTNAME] [-- <args>...]

OPTIONS:
    -q, --quiet                      Display one character per test instead of one line
        ...
        --features <FEATURES>...     Space-separated list of features to activate
        --all-features               Activate all available features

不过，两者cargo test --features foo testing_with_foo都不起作用。 …

我想实现一个线索为整数索引的序列。为了效率起见，重要的是节点的子节点通过索引序列而不是某种映射与节点相关联。为了说明基本思想，这里有一个 Ruby 实现：

require 'virtus'

class TrieNode
  include Virtus.model

  attribute :terminal, Boolean, default: false
  attribute :children, Array,   default: []

  def add(i, vec)
    if i == vec.length
      terminal = true
    else
      ( children[vec[i]] ||= TrieNode.new ).add i + 1, vec
    end
  end
end

这是 Perl 中的相同内容：

package TrieNode;
use Moo;

has terminal => ( is => 'rw' );
has children => ( is => 'ro', default => sub { [] } );

sub add {
   my ( $self, $i, …