erlang 如何从本地函数获取Elixir AST

shstlldc 于 2022-12-08 发布在 Erlang

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我想从作为参数传递的本地函数（如doSomething(fn a -> a * 10 end)）获取AST
所以我试着

def test do
    inspectAST(fn a,b -> a + b + 42 end)
    inspectAST(quote do: fn a,b -> a + b + 42 end)
    inspectFunctionInfo(fn a,b -> a + b + 42 end)
    :ok
  end

  def inspectAST(this_is_AST) do
    IO.inspect(this_is_AST)
    IO.inspect("--------------------------------")
  end

  def inspectFunctionInfo(fun) do
    IO.inspect(Function.info(fun))
    IO.inspect("--------------------------------")
  end

结果：

iex(3)> Utils.test
#Function<0.30424669/2 in Utils.test/0>
"--------------------------------"
{:fn, [],
 [
   {:->, [],
    [
      [{:a, [], Utils}, {:b, [], Utils}],
      {:+, [context: Utils, import: Kernel],
       [
         {:+, [context: Utils, import: Kernel],
          [{:a, [], Utils}, {:b, [], Utils}]},
         42
       ]}
    ]}
 ]}
"--------------------------------"
[
  pid: #PID<0.485.0>,
  module: Utils,
  new_index: 1,
  new_uniq: <<58, 7, 203, 172, 99, 108, 54, 80, 24, 151, 75, 56, 73, 174, 138,
    177>>,
  index: 1,
  uniq: 30424669,
  name: :"-test/0-fun-1-",
  arity: 2,
  env: [],
  type: :local
]
"--------------------------------"

我想要的是inspectAST(quote do: fn a,b -> a + b + 42 end)（AST）的结果，但我想发送类似inspectAST(fn a,b -> a + b + 42 end)的函数，而不发送quote do:
如果有人对此有一些想法，你的帮助将非常感激：）

erlang

来源：https://stackoverflow.com/questions/72543491/how-to-get-elixir-ast-from-local-function

1条答案

按热度按时间

hgb9j2n61#

If you want a "function" to be called on the AST, not values, it should be a macro, not a function.
The following should be a good base for what you want to achieve:

defmacro inspectAST(ast) do
    quote do
      IO.inspect(unquote(Macro.escape(ast)))
      :ok
    end
  end

  def test do
    inspectAST(fn a,b -> a + b + 42 end)
  end

you need to use defmacro to treat your parameter as AST, not a regular value
we want IO.inspect to happen at runtime, not compile time, so we need to return the AST for it using quote
what we want to inspect is the content of the ast variable, so we are using unquote
but unquote will unescape ast as well, so we need to escape it once more using Macro.escape/2

Please note that the macro should be defined before calling it, so defmacro has to be before test , not after.
For more advanced explanations about macros, you should check this serie of articles which is very detailed.

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erlang 如何从本地函数获取Elixir AST

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