I settled for:

(defmacro defcomponent [name co]
`(let [c# ~co]
  (assert (component? c# "Not a valid IComponent"))
  (def ~name c#)))

Jim

On 21/02/13 14:18, AtKaaZ wrote:
that one doesn't actually work, maybe, not sure why exactly but the assert is ignored

=> (def component? number?)
#'runtime.q/component?

=> (defmacro defcomponent [name co]
    `(assert (component? ~co) "Not a valid IComponent")
    `(def ~name ~co))
#'runtime.q/defcomponent

=> (defcomponent a "a")
#'runtime.q/a


The `(do ...) one works though,
=> (defmacro a []
     `(println 1)
     `(println 2)
     )
#'runtime.q/a
=> (a)
2
nil

=> (defmacro a []
     `(do
        (println 1)
        (println 2)
        )
     )
#'runtime.q/a
=> (a)
1
2
nil




On Thu, Feb 21, 2013 at 3:14 PM, Jim foo.bar <jimpil1...@gmail.com <mailto:jimpil1...@gmail.com>> wrote:

    I tried this and it works, but I need 2 backticks and I'm
    essentially generating the assert-form when the macro is
    called...I'd like to generate only the def-form at run-time...

    (defmacro defcomponent [name co]
      `(assert (component? ~co) "Not a valid IComponent")
      `(def ~name ~co))

    it looks ugly doesn't it?

    Jim




    On 21/02/13 14:11, AtKaaZ wrote:
    or you could place the assert inside the backquote


    On Thu, Feb 21, 2013 at 3:10 PM, Jim foo.bar
    <jimpil1...@gmail.com <mailto:jimpil1...@gmail.com>> wrote:

        On 21/02/13 14:07, Jim foo.bar wrote:

            Hi all,

            I''d like to have a macro like the following but
            preferably without the 'eval' inside the assertion form:

            (defmacro defcomponent [name co]
             (assert (component? (eval co)) "Not a valid IComponent")
             `(def ~name ~co))

            If I don't use eval, everything works as long as I pass a
            var in...However if I pass in something like (String.
            "jam") it is not being evaluated and thus is a list not
            an object...and it will never satisfy IComponent.

            any thoughts?
            thanks in advance :)

            Jim



        I could have phrased this better...One of my arguments has to
        NOT be evaluated (name) but the other needs to be evaluated
        (co) so I can assert whatever I want to assert on it...I
        cannot use 'defn' (it will cause 'name' to be evaluated) so
        my only option is a macro that forces eval on the second arg,
        yes?


        Jim

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