Re: How to get a value of a var in Java

[Justin Smith]

anyway - vars implement IFn, as far as I can see there's no real problem
here, you can deref the var object and it just happens to also implement IFn

(control-return adds a new line without sending in slack, but sends
immediately in gmail, clearly my brain is having trouble code switching
here)


On Thu, Jun 24, 2021 at 9:43 AM Justin Smith  wrote:

> (sorry, hit reply too soon)
>
> On Thu, Jun 24, 2021 at 9:42 AM Justin Smith  wrote:
>
>> >  Clojure vars under the IFn interface. In other words, you can only
>> import Clojure functions, not Clojure values, through that API.
>>
>> On Fri, Jun 18, 2021 at 12:29 PM ru  wrote:
>>
>>> Thank you, Gary, for the comprehensive answer. I have a control over
>>> Clojure side, so I decide to add special functions to get values of needed
>>> vars.
>>> Thanks to all for the help.
>>>
>>> Best regards,
>>>   Ru
>>>
>>> пятница, 18 июня 2021 г. в 20:23:31 UTC+3, gary.ve...@gmail.com:
>>>
 The official Clojure API for Java is defined here
  
 and
 only supports importing Clojure vars under the IFn interface. In other
 words, you can only import Clojure functions, not Clojure values, through
 that API. What you are trying to do is not supported.

 That does not mean it's impossible. If you control the Clojure side,
 the easiest approach is to just make a function and call that through the
 official API. If for some reason that's not an option, you can try
 gen-class , which may
 be faster.

 If you can't change the Clojure side, you'll have to use undocumented
 APIs. The Clojure.var
 
  call
 will return a Var
 
  (cast
 to the IFn
 
 interface), which has a deref()
 
 method that should get you the underlying value. This is undocumented so it
 may break and all that, but it really looks like all you need to do is cast
 that IFn back to a Var (or an IDeref
 ,
 as Chris suggested).

 Overall, I'd strongly recommend going through the documented API and
 just add a no-arg function.

 On Fri, 18 Jun 2021 at 12:53, ru  wrote:

> Dear Clojure users and team!
> Citation 1 from Clojure documentation:
>
> "Calling Clojure From Java..
> IFn plus = Clojure.var("clojure.core", "+");
> plus.invoke(1, 2);.."
>
> With functions all well but with def..
>
> Citation 2:
>
> "(def *symbol* *doc-string*? *init*?)
>
> Creates and interns or locates a global var
>  with the name of *symbol* and a
> namespace of the value of the current namespace (*ns*). "
>
> I can not figure out how to get the value of the symbol, created with
> def construct in Clojure and, for example, print it with 
> System.out.println
> in Java.
>
> I tried everything, nothing works! :(
>
> Any help would be greatly appreciated.
>
> Sincerely,
>
>   Ru
>
>
>
>
>
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Re: How to get a value of a var in Java

[Justin Smith]

(sorry, hit reply too soon)

On Thu, Jun 24, 2021 at 9:42 AM Justin Smith  wrote:

> >  Clojure vars under the IFn interface. In other words, you can only
> import Clojure functions, not Clojure values, through that API.
>
> On Fri, Jun 18, 2021 at 12:29 PM ru  wrote:
>
>> Thank you, Gary, for the comprehensive answer. I have a control over
>> Clojure side, so I decide to add special functions to get values of needed
>> vars.
>> Thanks to all for the help.
>>
>> Best regards,
>>   Ru
>>
>> пятница, 18 июня 2021 г. в 20:23:31 UTC+3, gary.ve...@gmail.com:
>>
>>> The official Clojure API for Java is defined here
>>>  
>>> and
>>> only supports importing Clojure vars under the IFn interface. In other
>>> words, you can only import Clojure functions, not Clojure values, through
>>> that API. What you are trying to do is not supported.
>>>
>>> That does not mean it's impossible. If you control the Clojure side, the
>>> easiest approach is to just make a function and call that through the
>>> official API. If for some reason that's not an option, you can try
>>> gen-class , which may
>>> be faster.
>>>
>>> If you can't change the Clojure side, you'll have to use undocumented
>>> APIs. The Clojure.var
>>> 
>>>  call
>>> will return a Var
>>> 
>>>  (cast
>>> to the IFn
>>> 
>>> interface), which has a deref()
>>> 
>>> method that should get you the underlying value. This is undocumented so it
>>> may break and all that, but it really looks like all you need to do is cast
>>> that IFn back to a Var (or an IDeref
>>> ,
>>> as Chris suggested).
>>>
>>> Overall, I'd strongly recommend going through the documented API and
>>> just add a no-arg function.
>>>
>>> On Fri, 18 Jun 2021 at 12:53, ru  wrote:
>>>
 Dear Clojure users and team!
 Citation 1 from Clojure documentation:

 "Calling Clojure From Java..
 IFn plus = Clojure.var("clojure.core", "+");
 plus.invoke(1, 2);.."

 With functions all well but with def..

 Citation 2:

 "(def *symbol* *doc-string*? *init*?)

 Creates and interns or locates a global var
  with the name of *symbol* and a
 namespace of the value of the current namespace (*ns*). "

 I can not figure out how to get the value of the symbol, created with
 def construct in Clojure and, for example, print it with System.out.println
 in Java.

 I tried everything, nothing works! :(

 Any help would be greatly appreciated.

 Sincerely,

   Ru





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 .

>>> --
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>> 

Re: How to get a value of a var in Java

[Justin Smith]

>  Clojure vars under the IFn interface. In other words, you can only
import Clojure functions, not Clojure values, through that API.

On Fri, Jun 18, 2021 at 12:29 PM ru  wrote:

> Thank you, Gary, for the comprehensive answer. I have a control over
> Clojure side, so I decide to add special functions to get values of needed
> vars.
> Thanks to all for the help.
>
> Best regards,
>   Ru
>
> пятница, 18 июня 2021 г. в 20:23:31 UTC+3, gary.ve...@gmail.com:
>
>> The official Clojure API for Java is defined here
>>  and
>> only supports importing Clojure vars under the IFn interface. In other
>> words, you can only import Clojure functions, not Clojure values, through
>> that API. What you are trying to do is not supported.
>>
>> That does not mean it's impossible. If you control the Clojure side, the
>> easiest approach is to just make a function and call that through the
>> official API. If for some reason that's not an option, you can try
>> gen-class , which may be
>> faster.
>>
>> If you can't change the Clojure side, you'll have to use undocumented
>> APIs. The Clojure.var
>> 
>>  call
>> will return a Var
>> 
>>  (cast
>> to the IFn
>> 
>> interface), which has a deref()
>> 
>> method that should get you the underlying value. This is undocumented so it
>> may break and all that, but it really looks like all you need to do is cast
>> that IFn back to a Var (or an IDeref
>> ,
>> as Chris suggested).
>>
>> Overall, I'd strongly recommend going through the documented API and just
>> add a no-arg function.
>>
>> On Fri, 18 Jun 2021 at 12:53, ru  wrote:
>>
>>> Dear Clojure users and team!
>>> Citation 1 from Clojure documentation:
>>>
>>> "Calling Clojure From Java..
>>> IFn plus = Clojure.var("clojure.core", "+");
>>> plus.invoke(1, 2);.."
>>>
>>> With functions all well but with def..
>>>
>>> Citation 2:
>>>
>>> "(def *symbol* *doc-string*? *init*?)
>>>
>>> Creates and interns or locates a global var
>>>  with the name of *symbol* and a
>>> namespace of the value of the current namespace (*ns*). "
>>>
>>> I can not figure out how to get the value of the symbol, created with
>>> def construct in Clojure and, for example, print it with System.out.println
>>> in Java.
>>>
>>> I tried everything, nothing works! :(
>>>
>>> Any help would be greatly appreciated.
>>>
>>> Sincerely,
>>>
>>>   Ru
>>>
>>>
>>>
>>>
>>>
>>> --
>>> 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.
>>> To view this discussion on the web visit
>>> https://groups.google.com/d/msgid/clojure/fcbd3883-705a-4180-9b99-7ccad64a09afn%40googlegroups.com
>>> 
>>> .
>>>
>> --
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> 
> .
>

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