I'm trying to make a macro that transform this:
(defn-check my-checked-function
check-function
[a A
b B]
(do-something a b))
into:
(defn my-checked-function [a b]
{:pre [(= (check-function a) A)
(= (check-function b) B)]}
(do-something a b))
I'm new to clojure, could anyone show me how to do that?
(defmacro defn-check [name check-fn args & tail]
(let [docstring (if (string? (first tail)) (first tail))
tail (if docstring (next tail) tail)
params (take-nth 2 args)
checks (take-nth 2 (next args))
cf (gensym "cf__")]
`(let [~cf ~check-fn]
(defn ~name
~@(if docstring [docstring])
~(vec params)
{:pre ~(mapv (fn [p c]
`(= (~cf ~p) ~c))
params
checks)}
~@tail))))
This allows you to specify a docstring if you'd like, but not an attribute map (see (doc defn); adding support for that would be straightforward).
Example:
user> (defn-check funky-add odd? [x true y false] "foo" (+ x y))
#'user/funky-add
user> (doc funky-add)
-------------------------
user/funky-add
([x y])
foo
nil
user> (funky-add 1 2)
3
user> (funky-add 2 1)
AssertionError Assert failed: (clojure.core/= (cf__2268 x) true) user/eval2269/funky-add--2270 (form-init1446120099766722611.clj:1)
