The precondition should be a vector of expressions.
(defn foo [x] {:pre [(not (nil? x))]} (* 3 x))
On Jan 9, 2012, at 12:53 PM, Tom Chappell wrote:
> Ok, I've got a couple thousand lines of Clojure under my belt, but
> this has me stumped, unless it's a compiler etc. issue. If I'm
> missing something dumb, what is it, please?
>
> I have a function that is failing a not-nil precondition. Here are
> four versions of the same test; only #3 works correctly. Obviously I
> can work around the problem, but am I doing something wrong?
>
> user> (def fq (frequencies "abbccc"))
> #'user/fq
>
> user> fq
> {\a 1, \b 2, \c 3}
>
> user> (fq \a)
> 1
>
> user> ; incorrectly fails :pre
> (defn test-fun1
> [mp k]
> {:pre (not (nil? (mp k)))}
> (mp k))
> #'user/test-fun1
>
> user> (test-fun1 fq \a)
>
> Assert failed: (nil? (mp k))
> [Thrown class java.lang.AssertionError]
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