in which case it does get evaluated twice if form: => (pred-transform (println 1) #(not (nil? %)) #(println % ".")) 1 1 nil . nil
=> (pred-transform (println 1) nil? #(println % ".")) 1 1 nil so maybe a let + gensym would be in order? On Sat, May 25, 2013 at 3:04 PM, atkaaz <atk...@gmail.com> wrote: > Shouldn't it be like: > > (definline pred-transform [obj pred tf] > `(if (~pred ~obj) ~obj > (~tf ~obj))) > => (pred-transform 1 #(not (nil? %)) println) > 1 > => (pred-transform 1 nil? println) > 1 > nil > > > > > On Sat, May 25, 2013 at 2:55 PM, atkaaz <atk...@gmail.com> wrote: > >> just wondering if obj is a form does it get evaluated twice? >> >> >> On Sat, May 25, 2013 at 2:51 PM, Jim - FooBar(); <jimpil1...@gmail.com>wrote: >> >>> no need for macros... :) >>> >>> (definline safe-assoc [m k v] >>> `(if (contains? ~m ~k) ~m >>> (assoc ~m ~k ~v))) >>> >>> (definline pred-transform [obj pred tf] >>> `(if ~(pred obj) ~obj >>> ~(tf obj))) >>> >>> Jim >>> >>> >>> >>> On 25/05/13 12:44, atkaaz wrote: >>> >>> may I see the macro for the latter, if you decide to go that way ? thx >>> >>> >>> On Sat, May 25, 2013 at 2:24 PM, Steven Degutis <sbdegu...@gmail.com>wrote: >>> >>>> There are two patterns I find in my code that I'm still unhappy with >>>> but I don't know how to clean up. >>>> >>>> The first is: (if (:attr obj) obj (assoc obj :attr something)) >>>> >>>> I'm basically saying, give this hash-map an attribute if it doesn't >>>> already have it. And just return the thing with an attribute, regardless if >>>> I had to add it or not. >>>> >>>> This version is ugly because it repeats obj three times. I could >>>> write my own macro to de-duplicate it, but I avoid doing that when I can >>>> because there's usually a better built-in solution that I just don't know >>>> about yet. >>>> >>>> The second is like it: (if (some-test obj) obj (some-transformation >>>> obj)) >>>> >>>> In this one, I just want to return the object, but maybe transform it >>>> first. But the reference to obj happens three times! Still feels like it >>>> could be cleaned up. >>>> >>>> Any thoughts on how to clean these up? >>>> -- >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "Clojure" group. >>>> To post to this group, send email to clojure@googlegroups.com >>>> Note that posts from new members are moderated - please be patient with >>>> your first post. >>>> To unsubscribe from this group, send email to >>>> clojure+unsubscr...@googlegroups.com >>>> For more options, visit this group at >>>> http://groups.google.com/group/clojure?hl=en >>>> --- >>>> You received this message because you are subscribed to the Google >>>> Groups "Clojure" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to clojure+unsubscr...@googlegroups.com. >>>> For more options, visit https://groups.google.com/groups/opt_out. >>>> >>>> >>>> >>> >>> -- >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To post to this group, send email to clojure@googlegroups.com >>> Note that posts from new members are moderated - please be patient with >>> your first post. >>> To unsubscribe from this group, send email to >>> clojure+unsubscr...@googlegroups.com >>> For more options, visit this group at >>> http://groups.google.com/group/clojure?hl=en >>> --- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to clojure+unsubscr...@googlegroups.com. >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >>> >>> >>> >>> -- >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To post to this group, send email to clojure@googlegroups.com >>> Note that posts from new members are moderated - please be patient with >>> your first post. >>> To unsubscribe from this group, send email to >>> clojure+unsubscr...@googlegroups.com >>> For more options, visit this group at >>> http://groups.google.com/group/clojure?hl=en >>> --- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to clojure+unsubscr...@googlegroups.com. >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >>> >>> >> >> > -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
