Re: Adding a new procedure to standard Scheme

[Jamison Hope <jrh at theptrgroup dot com>]

On May 27, 2011, at 4:03 PM, Charles Turner wrote:

> Hi,
>
> I'm trying to add a new procedure to the standard Scheme in Kawa.  
> The procedure is called write-ss and it's supposed to be a new  
> procedure in the lib.ports file, defined like so,
>
> (define (write-ss value #!optional (out (current-output-port))) ::  
> <void>
>  (*:format (kawa.standard.Scheme:.sharedWriteFormat) value out))
>
> The idea is for it to pick up a sub-class of DisplayFormat called  
> SSDisplayFormat, so I added the following to kawa.standard.Scheme,
>
> defProcStFld("write-ss", "kawa.lib.ports");
>
> and
>
> public static final AbstractFormat sharedWriteFormat = new  
> SSDisplayFormat(true, 'S');
>
> SSDisplayFormat is just overriding #writeList and #writeObjectRaw  
> from DisplayFormat.
>
> So everything compiles fine, but I get the following exception in  
> the REPL when I try to make sure it's picked up,
>
> #|kawa:3|# write-ss
> <unknown>: exception loading 'write-ss' - null
>
> I realise I haven't shown you what's happening in SSDisplayFormat,  
> just because it's quite long and I figured the problem is I'm not  
> registering the new procedure properly in Kawa.
>
> Any thoughts?
>
> Thanks for your time,
>
> Charlie.

That ought to work. I just tried adding a function to ports.scm:

(define (jrh-foo x) ::void
  (display x) (newline))

and to Scheme.java's kawaEnvironment:

      defProcStFld("jrh-foo", "kawa.lib.ports");

and after recompiling with ant,

#|kawa:1|# jrh-foo
#<procedure jrh-foo>

Are you sure that kawa/lib/ports.scm got rebuilt after you added your  
function? If I delete my function but leave the defProcStFld line in  
Scheme.java and recompile, then I see an error like yours:

#|kawa:1|# jrh-foo
<unknown>: exception loading 'jrh-foo' - null

If I also remove the defProcStFld call (reverting the last of my  
changes), then the REPL error is different:

#|kawa:1|# jrh-foo
<unknown>: warning - no declaration seen for jrh-foo
unbound location jrh-foo
[followed by stack trace]


The first thing I would try (after double-checking that the spelling  
matches in both places) would be to do `make clean` or `ant clean` or  
whatever to be sure that you aren't inadvertently picking up an old  
class file or an old jar file.

Jamie

--
Jamison Hope
The PTR Group
www.theptrgroup.com