Re: why not apply-macro

2014-02-25 Thread 刘家财 
hi JW,
First thank you for your reply.
my origin question is somethine about redis.here i refer 
https://github.com/ptaoussanis/carmine 
I follow this two line
 (def server1-conn {:pool {opts} :spec {opts}}) ; See `wcar` docstring 
for opts

(defmacro wcar* [ body] `(car/wcar server1-conn ~@body))

then I can exec some redis commands,but I want to exec commands dynamicly.
for example I here a vector [[foo bar][hello world]]
i want to exec following commands
(wcar* (car/set foo bar) (car/set hello world))
so i have write a macro like this

(defmacro batchly-redis [cmd params] 
  (let [car-fns (map #(cons cmd %) params)]
`(wcar* ~@car-fns)))


then I can invoke this macro using this way
(batchly-redis cat/set [[foo bar][hello world]])
in this way,my macro works ok.but here my vector is coming from the return 
of other fn ,so as you said above,this will not work, because marco 
evaluates args at compile time.Do your have some ideas on my problem.
Really thanks


在 2014年2月24日星期一UTC+8下午6时29分09秒，Jozef Wagner写道：

 Well the evil thing is that apply-macro evaluates arguments at compile 
 time. Example where this won't work follows

 (defn foo [numbers]
   (apply-macro + numbers))

 JW


 On Mon, Feb 24, 2014 at 10:27 AM, 刘家财 jiaca...@gmail.com javascript:wrote:

 I have one problem using Clojure
 we all know there is a apply for a fn to prepend intervening arguments to 
 args. 
 such as (apply + [2 3]) will equals to (+ 2 3)
 this is really handy,
 BUT,this is no apply-macro fn to use,I find a contrib(
 https://github.com/clojure/clojure-contrib/blob/73accf597eafb8dfcb642702a3b98b057bbdbbdf/src/main/clojure/clojure/contrib/apply_macro.clj#L34)
  
 which has somethine like this,but deprecated.
 and says it is evil,I can't understand why the docs says it was evil?
 Is there anything harmful? Can someone show me some examples?
 Thank U


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Re: why not apply-macro

2014-02-25 Thread 刘家财 
Hi James,
I really appreciate your code,it really help me much.
just a little modification:

(defn batchly-redis [cmd params]
  (doseq [p params]
(apply cmd p)))

doseq requires an even number of args

在 2014年2月25日星期二UTC+8下午6时33分48秒，James Reeves写道：

 You could just write it as a function and leave out wcar*.

 (defn batchly-redis [cmd params]
   (doseq [params]
 (apply cmd params)))

 Then to execute:

 (wcar* (batchly-redis cat/set parameters))

 As far as I can tell, wcar is just a container macro, like with-open, in 
 that it initiates the connection and then cleans up after itself. Within 
 wcar, you can execute functions in whatever way you want.

 - James


 On 25 February 2014 09:00, 刘家财 jiaca...@gmail.com javascript: wrote:

 hi JW,
 First thank you for your reply.
 my origin question is somethine about redis.here i refer 
 https://github.com/ptaoussanis/carmine 
 I follow this two line
  (def server1-conn {:pool {opts} :spec {opts}}) ; See `wcar` 
 docstring for opts

 (defmacro wcar* [ body] `(car/wcar server1-conn ~@body))

 then I can exec some redis commands,but I want to exec commands dynamicly.
 for example I here a vector [[foo bar][hello world]]
 i want to exec following commands
 (wcar* (car/set foo bar) (car/set hello world))
 so i have write a macro like this

 (defmacro batchly-redis [cmd params] 
   (let [car-fns (map #(cons cmd %) params)]
 `(wcar* ~@car-fns)))


 then I can invoke this macro using this way
 (batchly-redis cat/set [[foo bar][hello world]])
 in this way,my macro works ok.but here my vector is coming from the 
 return of other fn ,so as you said above,this will not work, because marco 
 evaluates args at compile time.Do your have some ideas on my problem.
 Really thanks


 在 2014年2月24日星期一UTC+8下午6时29分09秒，Jozef Wagner写道：

 Well the evil thing is that apply-macro evaluates arguments at compile 
 time. Example where this won't work follows

 (defn foo [numbers]
   (apply-macro + numbers))

 JW


 On Mon, Feb 24, 2014 at 10:27 AM, 刘家财 jiaca...@gmail.com wrote:

 I have one problem using Clojure
 we all know there is a apply for a fn to prepend intervening arguments 
 to args. 
 such as (apply + [2 3]) will equals to (+ 2 3)
 this is really handy,
 BUT,this is no apply-macro fn to use,I find a contrib(
 https://github.com/clojure/clojure-contrib/blob/
 73accf597eafb8dfcb642702a3b98b057bbdbbdf/src/main/clojure/
 clojure/contrib/apply_macro.clj#L34) which has somethine like this,but 
 deprecated.
 and says it is evil,I can't understand why the docs says it was evil?
 Is there anything harmful? Can someone show me some examples?
 Thank U


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why not apply-macro

2014-02-24 Thread 刘家财 
I have one problem using Clojure
we all know there is a apply for a fn to prepend intervening arguments to 
args. 
such as (apply + [2 3]) will equals to (+ 2 3)
this is really handy,
BUT,this is no apply-macro fn to use,I find a contrib(
https://github.com/clojure/clojure-contrib/blob/73accf597eafb8dfcb642702a3b98b057bbdbbdf/src/main/clojure/clojure/contrib/apply_macro.clj#L34)
 
which has somethine like this,but deprecated.
and says it is evil,I can't understand why the docs says it was evil?
Is there anything harmful? Can someone show me some examples?
Thank U


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