Ah seems the repl state was the cause, restarted and the ordering worked
correctly though it still confuses me greatly! but I'll get there
eventually (I hope). as for the extra ')' that was manually retyping into
forum error :)
Using nightcode editor's insta-repl for testing and seems it doesn't
refresh the changes. Also does mutlimethod handle varargs? purely for
testing purposes, doubt it'll be used but just incase
On Wednesday, 11 January 2017 22:29:00 UTC, Alex Miller wrote:
>
>
>
> On Wednesday, January 11, 2017 at 4:23:28 PM UTC-6, david swift wrote:
>>
>> Been working on a tiny snippet of code related to multimethods (something
>> I've never quite wrapped my head around) and when it comes to the
>> dispatching of the function I'm confused by the order in which I've to pass
>> the arguments in as it seems to go against all common sense.
>>
>> To show what I am trying to do (to begin with); ignoring name
>> conflictions. Without implementing algorithm details I supply a simple
>> string for ease.
>> (defmulti transform (fn [language data] language))
>>
>> (defmethod transform :html
>> [_ data]
>> (str data " will be transformed into html")))
>>
>
> ^ extra ) at the end there fyi
>
>
>>
>>
>> (defmethod transform :java-fx
>> [_ data]
>> (str data " will be transformed into javafx"))
>>
>> What I would expect from this outcome would be to do the following on
>> dispatch
>> (transform :html "some data") => "some data will be transformed into
>> html"
>>
>
> This is what I see and that looks right to me. I suspect you somehow have
> old method impls in your repl state. You should try with a fresh repl.
>
>
>>
>> But instead the output I actually get ends up being
>> "some data"
>> which I assume to be the default for mulitmethods to return the data
>> value. Though if I were to instead to change the order of the arguments
>> like so.
>>
>> (transform "some data" :html) => "some data will be transformed into
>> html"
>> The expect outcome I wanted but not with the "correct" argument order I
>> was expecting, and to also note this (for me) prevents me from having more
>> than one argument and dispatch case.
>>
>
> I get
>
> IllegalArgumentException No method in multimethod 'transform' for dispatch
> value: some data clojure.lang.MultiFn.getFn (MultiFn.java:156)
>
>
> I know that I can do this approach
>> (transform {:language :html} "some data")
>> and it would work in the correct order but it's extra data I'm looking to
>> avoid for the sake of correct argument order
>>
>> Ideally I would of like the code to look something like below
>> (defmulti transform :language)
>>
>> (defmethod transform :html
>> [data]
>> (str data " will be transformed into html"))
>>
>> (defmethod transform :java-fx
>> [data]
>> (str data " will be transformed into javafx"))
>>
>> I'd be grateful if someone could give me some simple examples to go by
>> that work by keyword dispatch that isn't foobaz, thank you :)
>>
>
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