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Re: Using Kawa as an embedded scripting language

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 \"\")") it works just

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 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

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