Help with macro.

[Andrey Antukh]

Hi!

I have a little trouble writing a macro because I'm getting unexpected (for me) behavior.

Let see some code:

(ns foo.bar)

(defn debug

  [x]

  (println "debug:" x)

  x)

(defn debug-expr?

  [expr]

  (and (seq? expr)

       (symbol? (first expr))

       (= 'foo.bar/debug  (first expr))))

(defmacro without-debug

  [& body]

  (let [body' (reduce (fn [acc v]

                        (if (debug-expr? v)

                          (conj acc (second v))

                          (conj acc v)))

                      [] body)]

    `(do

       ~@body')))

And then I use it from other namespace:

(ns foo.baz)

(require '[foo.bar :as b])

(macroexpand '(b/without-debug (b/debug 3)))

;; => (do (b/debug 3))

(macroexpand '(b/without-debug (foo.bar/debug 3)))

;; =>(do 3)

  

I expect that the both expressions will evaluate to the same result, but is not. Seems that symbols inside macros are not fully qualified. It there any way to get them fully qualified? I'm missing something?

Any help is welcome!

Thank you very much.

Andrey

--

Andrey Antukh - Андрей Антух - <ni...@niwi.nz>

http://www.niwi.nz

https://github.com/niwinz

[gianluca torta]

Hi,

the behavior you describe is not specific to macros, but is due to the use of aliases

after:

(require '[foo.bar :as b])

this will give you false:
(= 'foo.bar/x (first '(b/x)))

while this will give you true:
(= 'foo.bar/x (first '(foo.bar/x)))

one way to solve it, is comparing the resolved vars instead of the names:
(= (resolve 'foo.bar/x) (resolve (first '(b/x))))
;=>true
(= (resolve 'foo.bar/x) (resolve (first '(foo.bar/x))))
;=>true

hth,
Gianluca

[Andrey Antukh]

On Sat, Oct 3, 2015 at 5:24 PM, gianluca torta <giat...@gmail.com> wrote:

Hi,

the behavior you describe is not specific to macros, but is due to the use of aliases

after:
(require '[foo.bar :as b])

this will give you false:
(= 'foo.bar/x (first '(b/x)))

while this will give you true:
(= 'foo.bar/x (first '(foo.bar/x)))

one way to solve it, is comparing the resolved vars instead of the names:
(= (resolve 'foo.bar/x) (resolve (first '(b/x))))
;=>true
(= (resolve 'foo.bar/x) (resolve (first '(foo.bar/x))))
;=>true

Yes, your solution works, but only on clojure. ClojureScript doesn't have `resolve`. It there any portable solution?

Thanks!

Andrey

 

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[gianluca torta]

Yes, your solution works, but only on clojure. ClojureScript doesn't have `resolve`. It there any portable solution?

I'm not sure if and how you can do it in ClojureScript... have you tried:
https://groups.google.com/forum/#!forum/clojurescript

cheers,
Gianluca