If you want keywords to participate in a multimethod hierarchy, you must qualify them.
You can however make up some namespace and use it throughout your code, so instead of ::foo, you'll use :my-ns/foo. This namespace don't have to the current or even a real one. Jozef On Saturday, August 9, 2014 9:49:58 PM UTC+2, larry google groups wrote: > > Thank you for the responses. However, when I look here: > > http://clojure.org/multimethods > > I see that it says: > > "You can define hierarchical relationships with (derive child parent). > Child and parent can be either symbols or keywords, and must be > namespace-qualified" > > Is there any way I can establish a hierarchical relationship without it > being name-spaced qualified? I would like to be able to (slingshot/throw+ > {:type some-symbol}) and have this be caught in a different namespace, but > I need a way to match the some-symbol, and I would ideally like it if > some-symbol > might be part of a hierarchy, such that I'm matching again some-symbol's > parent. > > Is that possible? > > I guess I could hard-code all of the namespaces, such that the symbols are > all: > > some-namespace/some-symbol > > but that does great reduce the flexibility of the system. > > > > > > > On Saturday, August 9, 2014 3:30:33 PM UTC-4, James Reeves wrote: >> >> Jozef is correct, but to give some examples: >> >> (ns example.core >> (:require [example.other :as other])) >> >> (= ::foo :example.core/foo) >> (= ::other/foo :example.other/foo) >> >> (not= :foo :example.core/foo) >> (not= :example.core/foo :example.other/foo) >> (not= :other/foo ::other/foo) >> >> - James >> >> >> >> On 9 August 2014 19:14, Jozef Wagner <jozef....@gmail.com> wrote: >> >>> Keep in mind that :: is just a syntax sugar that is processed by the >>> reader, before the compiler kicks in. ::foo is a shorthand for >>> :your.current.ns/foo. Its purpose is to make it easy to create keywords >>> that do not clash with other ones. >>> >>> Keywords are equal (and identical) only when both of their namespaces >>> and names are equal. :ns1/foo is thus not equal to :ns2/foo, nor to just >>> :foo. :: is used in cases where you want to exploit this important >>> property of keywords, so that your keyword won't e.g. clash with other >>> keywords in a collection, contents of which you don't know. >>> >>> Jozef >>> >>> >>> On Saturday, August 9, 2014 7:46:45 PM UTC+2, larry google groups wrote: >>>> >>>> Please forgive this stupid question, but I'm still trying to understand >>>> exactly what the double "::" means. I have read that I can use (derive) to >>>> establish a hierarchy and I can imagine how this would be useful for >>>> things >>>> like throwing errors and catching them and logging, but I've also read >>>> that >>>> "::" adds the namespace to the symbol, so I would assume that I can not >>>> match ::logging from one namespace with ::logging from another? >>>> >>>> I'm thinking of this especially in my use of Slingshot, where I was >>>> thinking of doing something like: >>>> >>>> (throw+ {:type ::database-problem :message "something wrong in the >>>> database query"}) >>>> >>>> and then at a higher level in my code I was going to catch it with >>>> something like: >>>> >>>> (derive ::database-problem ::logging) >>>> >>>> and then using Dire: >>>> >>>> (dire/with-handler! #'database/remove-this-item >>>> [:type ::logging] >>>> (fn [e & args] >>>> (timbre/log (str " database/remove-this-item: The time : " >>>> (dates/current-time-as-string) ( str e)))) >>>> >>>> but conceptually I am having trouble understanding how ::logging in one >>>> namespace can match ::logging in another namespace. Perhaps I should just >>>> use normal keywords? >>>> >>>> >>>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To post to this group, send email to clo...@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+u...@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+u...@googlegroups.com. >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- You received this message because you are subscribed to the Google Groups "Clojure" group. 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