Controlling symbol generation in Clojure macros
- by mikera
I'm trying (as a self-learning exercise) to create a Clojure macro that will generate code to apply a function to a sequence of integers and sum the result, e.g.
f(0) + f(1) + f(2) + f(3)
This is my attempt:
(defmacro testsum [func n]
`(fn [x#] (+ ~@( map (fn [i] `(~func x#)) (range n)))))
However something seems to go wrong with the x# gensym and I end up with two different versions of x and hence the function doesn't work:
(macroexpand '(testsum inc 3))
gives:
(fn* ([x__809__auto__]
(clojure.core/+
(inc x__808__auto__)
(inc x__808__auto__)
(inc x__808__auto__))))
This is pretty much exactly what I want apart from the different 809 and 808 versions of x.....
What am I doing wrong? I thought that the auto gensym was meant to create a single unique symbol for exactly this kind of purpose? Is there a better way of doing this?
