Clojure:如何获取函数的元数据？

Question

我正在尝试获取所有内置 Clojure 函数的元数据。

在 previous question我了解到这可以使用类似 ^#'func_name (获取 var 对象的元数据)来实现。但我没能以编程方式做到这一点，因为事先不知道 func-name 。

例如尝试获取 clojure.core 中最后一个函数的元数据:

user=> (use 'clojure.contrib.ns-utils)
nil
user=> (def last-func (last (vars clojure.core)))

user=> last-func
zipmap

;The real metadata (zipmap is hardcoded)
user=> ^#'zipmap
{:ns #<Namespace clojure.core>, :name zipmap, :file "clojure/core.clj", :line 1661, :arglists ([keys vals]), :doc "Returns a map .."}

;Try to get programmatically, but get shit
user=> ^#'last-func
{:ns #<Namespace user>, :name last-func, :file "NO_SOURCE_PATH", :line 282}

如何才能做到呢？我已经尝试了多种变体，但没有任何效果。

Answer 1

您正在寻找meta和ns-resolve。

user=> (let [fun "map"] (meta (ns-resolve 'clojure.core (symbol fun))))
{:ns #<Namespace clojure.core>, :name map, :file "clojure/core.clj", :line 1705, :arglists ([f coll] [f c1 c2] [f c1 c2 c3] [f c1 c2 c3 & colls]), :doc "Returns a lazy sequence consisting of the result of applying f to the\n  set of first i tems of each coll, followed by applying f to the set\n  of second items in each coll, until any one of the colls is\n  exhausted.  Any remaining items in other colls are ignored. Function\n  f should accept number-of-colls arguments."}