获取列表clojure中的元素类型

Question

I have a quoted expression eg

(def foo '(+ 1 (bar)))

I want to be able to find the type of any element of this list, eg to do something like

(type (second foo))

I get different results depending on the type of value, for example the following both evaluate to java.lang.Double, which is what I would want

(type '3.0)
(type 3.0)

Yet

(type '+)
(type +)

yields respectively

clojure.lang.Symbol
clojure.core$_PLUS_

I thought perhaps the resolve key would help yet

(type (resolve '+))

evaluates to:

clojure.lang.Var

Answer 1

There are just symbols '+ , 'bar and self-evaluating object 1 (long) in your list

(= '(+ 1 (bar))
   (list '+ '1 (list 'bar)))
=> true

Use eval .

(type (eval '+)) 
=> clojure.core$_PLUS_

And

(type '3.0) = (type 3.0) = (type (eval '3.0)) = java.lang.Double

because numbers are self-evaluating objects.

Answer 2

取消引用已解决的Var：

(type (deref (resolve '+)))