On Monday, March 31, 2014 12:13:25 PM UTC-5, Jony Hudson wrote:
>
>
> (defmacro functionalise
>   [ex var]
>   (let [arg (gensym)
>         body (postwalk-replace {var arg} ex)]
>     `(fn [~arg] ~body)))
>
>
This works as written, it is just that macros do not evaluate their 
arguments, so you do not want to quote you expression. 

(def foo (functionalise (+ 2 x) x))
(foo 40) ;=> 42

If you are working with quoted expressions, you'll have to eval in the 
macro and take the one-time hit there

(defmacro functionalise2
  [ex var]
  (let [arg (gensym)
        body (clojure.walk/postwalk-replace {var arg} ex)]
    `(fn [~arg] ~(eval body))))

(def foo2 (functionalise2 '(+ 2 x) x))
(foo2 40) ;=> 42

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