Re: Java enum in JPL

It seems Java 1.5+ enums are syntactic sugar for constructs which Java 
1.4 (and hence JPL) understands: given

public class Foo {
     public enum Bar {
         UP, DOWN
     }
     public static String legend(Bar x) {
         switch(x) {
             case UP:
                 return "upwards";
             case DOWN:
                 return "downwards";
             default:
                 return "?";
         }
     }
}

we can do

   1 ?- jpl_get('Foo$Bar', 'UP', X).
   X = @('J#00000000000056425292').

or

   1 ?- jpl_get('Foo$Bar', 'UP', X), jpl_call('Foo', legend, [X], S).
   X = @('J#00000000000056425292'),
   S = upwards.

where X is bound to the nominated enum constant (actually an object 
reference), then passed as an arg to legend/1

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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