Re: Using Kawa as an embedded scripting language

[Jamison Hope <jrh at theptrgroup dot com>]

On Aug 25, 2011, at 1:45 PM, John-Paul Verkamp wrote:

> I'm writing a project uses Kawa as an embedded scripting language, but
> one part of the behavior is a little puzzling.
>
> I'm doing this:
>
> Scheme kawa = new Scheme();
> kawa.eval("(define add1 (lambda (n) (+ n 1)))");
>
> But when I try to use the add1:
>
> Object result = kawa.eval("(add1 5)");
>
> I'm getting a NoSuchFieldError from the ModuleExp class.
>
> Alternatively, if I use kawa.defineFunction(...) to define add1 or put
> in in a file and use kawa.eval("(load \"add1.ss\")") it works just
> fine.
>
> I managed to work around the issue for the time being by automatically
> wrapping any top-level S-expressions that I pass to kawa.eval with
> Scheme's eval; for example:
> kawa.eval("(eval '(define add1 (lambda (n) (+ n 1))))")
>
> But that feels hacky (and doesn't work with some more complicated  
> forms).
>
> Is there something I'm doing wrong / should be doing to make this  
> work?
>
> Thanks ahead of time for any assistance.

I'm not sure why that doesn't work, but I'm guessing that the one- 
argument
eval isn't using the right Environment. Try this instead:

    Scheme.registerEnvironment();
    Scheme kawa = Scheme.getInstance(); // or new Scheme();
    Environment env = Environment.getCurrent();

    kawa.eval("(define add1 (lambda (n) (+ n 1)))", env);

    Object result = kawa.eval("(add1 5)", env);

That works for me.

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