Macros 长生不老药宏观扩张的问题,但只有在一个理解
作为我们开发图书俱乐部工作的一部分,我用Elixir编写了一个随机密码生成器。决定玩元编程,用宏来编写它,让事情干涸一点 这非常有效:Macros 长生不老药宏观扩张的问题,但只有在一个理解,macros,elixir,Macros,Elixir,作为我们开发图书俱乐部工作的一部分,我用Elixir编写了一个随机密码生成器。决定玩元编程,用宏来编写它,让事情干涸一点 这非常有效: # lib/macros.ex defmodule Macros do defmacro define_alphabet(name, chars) do len = String.length(chars) - 1 quote do def unquote(:"choose_#{name}")(chosen, 0) do
# lib/macros.ex
defmodule Macros do
defmacro define_alphabet(name, chars) do
len = String.length(chars) - 1
quote do
def unquote(:"choose_#{name}")(chosen, 0) do
chosen
end
def unquote(:"choose_#{name}")(chosen, n) do
alphabet = unquote(chars)
unquote(:"choose_#{name}")([(alphabet |> String.at :random.uniform(unquote(len))) | chosen], n - 1)
end
end
end
end
# lib/generate_password.ex
defmodule GeneratePassword do
require Macros
Macros.define_alphabet :alpha, "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
Macros.define_alphabet :special, "~`!@#$%^&*?"
Macros.define_alphabet :digits, "0123456789"
def generate_password(min_length, n_special, n_digits) do
[]
|> choose_alpha(min_length - n_special - n_digits)
|> choose_special(n_special)
|> choose_digits(n_digits)
|> Enum.shuffle
|> Enum.join
end
end
我想在Dict/map,甚至是列表中定义字母表,然后迭代调用Macros.define_alphabet,而不是手动调用它3次。然而,当我尝试使用下面的代码时,无论我使用什么结构来保存字母表,编译都会失败
alphabets = %{
alpha: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ",
special: "~`!@#$%^&*?",
digits: "0123456789",
}
for {name, chars} <- alphabets, do: Macros.define_alphabet(name, chars)
我试过让字母表映射为列表列表、元组列表、原子映射->字符串和字符串->字符串,这似乎并不重要。我还尝试将这些对管道化到Enum.each中,而不是使用“for”理解,如下所示:
alphabets |> Enum.each fn {name, chars} -> Macros.define_alphabet(name, chars) end
它们都给出了相同的结果。认为这可能与调用:random.uniform有关,并将其更改为:
alphabet |> to_char_list |> Enum.shuffle |> Enum.take(1) |> to_string
这只是将错误稍微更改为:
Erlang/OTP 18 [erts-7.1] [source] [64-bit] [smp:8:8] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]
== Compilation error on file lib/generate_password.ex ==
** (Protocol.UndefinedError) protocol String.Chars not implemented for {:name, [line: 24], nil}
(elixir) lib/string/chars.ex:3: String.Chars.impl_for!/1
(elixir) lib/string/chars.ex:17: String.Chars.to_string/1
expanding macro: Macros.define_alphabet/2
lib/generate_password.ex:24: GeneratePassword (module)
(elixir) lib/kernel/parallel_compiler.ex:100: anonymous fn/4 in Kernel.ParallelCompiler.spawn_compilers/8
即使有这样的更改,当我手动调用宏.define_alphabet(如顶部)时,它也可以正常工作,但在任何理解或使用Enum.each时都不行
这不是什么大问题,但我希望能够根据用户定义的配置以编程方式在字母表列表中添加和删除字母表
我相信,随着我深入研究,我会弄明白这一点,但如果有人有任何建议,我将不胜感激。列表理解是一种使用一个列表并从中获取另一个列表(或在一般情况下可枚举)的方法。在您的情况下,您不希望获得新列表,而是希望在模块中定义函数。所以,列表理解不是合适的方法
您可以使用另一个宏从地图定义字母表。解决了这个问题。如果我将bind_quoted列表传递给quote,则无论哪种方式都有效,尽管我还没有找到一种方法来预先计算长度并像以前一样使用:random.uniform,以避免为每个字符选择进行整个列表转换
# lib/macros.ex
defmodule Macros do
defmacro define_alphabet(name, chars) do
quote bind_quoted: [name: name, chars: chars] do
def unquote(:"choose_#{name}")(chosen, 0) do
chosen
end
def unquote(:"choose_#{name}")(chosen, n) do
unquote(:"choose_#{name}")([(unquote(chars) |> to_char_list |> Enum.shuffle |> Enum.take(1) |> to_string) | chosen], n - 1)
end
end
end
end
现在我可以用我喜欢的任何方式来称呼它:
# lib/generate_password.ex
defmodule GeneratePassword do
require Macros
alphabets = [
alpha: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ",
special: "~`!@#$%^&*?",
digits: "0123456789",
]
for {name, chars} <- alphabets do
Macros.define_alphabet name, chars
end
# or alphabets |> Enum.map fn {name, chars} -> Macros.define_alphabet name, chars end
# or Macros.define_alphabet :alpha2, "abcd1234"
def generate_password(min_length, n_special, n_digits) do
[]
|> choose_alpha(min_length - n_special - n_digits)
|> choose_special(n_special)
|> choose_digits(n_digits)
|> Enum.shuffle
|> Enum.join
end
end
输出:
iex> 1..20 |> Enum.map(fn _ -> PasswordGenerator.generate_password(20, 3, 3) end)
["01?dZQRhrHAbmP*vF3I@", "UUl3O0vqS^S3CQDr^AC$", "%1NOF&Xyh3Cgped*5xnk",
"Scg$oDVUB8Vx&b72GB^R", "SnYN?hlc*D03bW~5Rmsf", "R5Yg6Zr^Jm^!BOCD8Jjm",
"ni^Cg9BBQDne0v`M`2fj", "L8@$TpIUdEN1uy5h@Rel", "6MjrJyiuB26qntl&M%$L",
"$9hTsDh*y0La?hdhXn7I", "6rq8jeTH%ko^FLMX$g6a", "7jVDS#tjh0GS@q#RodN6",
"dOBi1?4LW%lrr#wG2LIu", "S*Zcuhg~R4!fBoij7y2o", "M!thW*g2Ta&M7o7MpscI",
"r5n3$tId^OWX^KGzjl4v", "L2CLJv&&YwncF6JY*5Zw", "DJWT`f6^3scwCO4pQQ*Q",
"mm2jVh5!J!Zalsuxk8&o", "O#kqGRfHGnu042PS`O*A"]
我不知道这个问题的答案,但这可能会对您有所帮助:当您向宏传递参数时,您传递的是AST表示。如果传递的是
“string”
或:atom
,它们将作为文本传递,而当传递变量时,它们将作为变量在Elixir AST中的表示方式传递:{:name,[line:24],Elixir}
@davoclavo:看起来这就是问题所在。制作了第二个宏,该宏接受list/dict,并且它可以完美地工作,除非(再次)list是一个变量。将其作为变量传入会给出“{:alphabets,[line:14],nil}”未实现的“(Protocol.UndefinedError)协议可枚举性,因此看起来它得到的是Macro.var的结果,我不确定如何将其扩展到实际值,或者是否应该。
defmodule ChooseFrom do
defmacro __using__(_options) do
quote do
import unquote(__MODULE__)
end
end
defmacro alphabet(name, chars) when is_binary(chars) do
function_name = :"choose_#{name}"
quote do
defp unquote(function_name)(remaining) when is_integer(remaining) and remaining > 0 do
unquote(function_name)([], remaining)
end
defp unquote(function_name)(chosen, remaining) when is_integer(remaining) and remaining > 0 do
next_char = Enum.random(unquote(String.graphemes(chars)))
unquote(function_name)([next_char | chosen], remaining - 1)
end
defp unquote(function_name)(chosen, _), do: chosen
end
end
end
defmodule PasswordGenerator do
use ChooseFrom
alphabet(:alpha, "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
alphabet(:digits, "0123456789")
alphabet(:special, "~`!@#$%^&*?")
def generate_password(min_length, num_special, num_digits) do
num_alpha = min_length - num_special - num_digits
num_alpha
|> choose_alpha()
|> choose_special(num_special)
|> choose_digits(num_digits)
|> Enum.shuffle()
|> Enum.join()
end
end
iex> 1..20 |> Enum.map(fn _ -> PasswordGenerator.generate_password(20, 3, 3) end)
["01?dZQRhrHAbmP*vF3I@", "UUl3O0vqS^S3CQDr^AC$", "%1NOF&Xyh3Cgped*5xnk",
"Scg$oDVUB8Vx&b72GB^R", "SnYN?hlc*D03bW~5Rmsf", "R5Yg6Zr^Jm^!BOCD8Jjm",
"ni^Cg9BBQDne0v`M`2fj", "L8@$TpIUdEN1uy5h@Rel", "6MjrJyiuB26qntl&M%$L",
"$9hTsDh*y0La?hdhXn7I", "6rq8jeTH%ko^FLMX$g6a", "7jVDS#tjh0GS@q#RodN6",
"dOBi1?4LW%lrr#wG2LIu", "S*Zcuhg~R4!fBoij7y2o", "M!thW*g2Ta&M7o7MpscI",
"r5n3$tId^OWX^KGzjl4v", "L2CLJv&&YwncF6JY*5Zw", "DJWT`f6^3scwCO4pQQ*Q",
"mm2jVh5!J!Zalsuxk8&o", "O#kqGRfHGnu042PS`O*A"]