Re: Java enum in JPL

JPL was conceived before Java acquired enums (in 1.5) and is still 
compiled to target Java 1.4, so it is enum-oblivious :-/

It's a JNI application, and so I guess we first need to understand how 
the JNI handles enums.

JPL is entirely "call-by-name", so maybe it should treat enums as 
opaque values; first you would jpl_get/3 the value of the named enum 
field, then pass it back as an arg?

Do enums correspond to anything which Java 1.4 knows about?

How would we do this from C/C++?

Paul Singleton


On 18/07/2013 12:14, Jerry wrote:
> All,
>
> I have been researching the web to find out how to create enum variables in
> JPL. So far I have found now examples and trial and error has been mostly
> error. Here is the fragment I need to emulate from SWI Prolog:
>
>
>      ArrayList< String > namesOfInterest = new ArrayList< String >();
>
>      AppTierSourceUsageRequestMessage.MessageType messageType =
>        getInvokeArgs( args, namesOfInterest );
>
>      ArrayList< String > result = null;
>
>      try {
>        result = invoke( messageType, namesOfInterest );
>      }
>      catch( CannotProcessException ex ) {
>        System.out.println( "MakeAppTierRequest.invoke() failed! Got ex=" +
> ex );
>        System.exit( 1 );
>      }
>
>
> MessageType is an enum. I know how to make an array of strings as needed
> for the 2nd argument of invoke but not so much luck with the first
> argument. I want to pass the constant enum value:
> GET_FILE_NAMES_AND_TOKEN_NAMES.
>
> My call so far looks like:
>
>      jpl_call( 'com.xxxxxx.xxxxx.messages.MakeAppTierRequest', invoke,
> ['????',Ac], F),
> Ac is an array of Strings and seems to be correct.
>
>
> Any thoughts or example uses of enum variables in JPL would be appreciated!
>
> Thanks!
>
> Jerry
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