Re: JESS: Binding a lambda function to a variable

[Eithon Cadag]

Thank you -- that's the exact solution I was searching for, and it works 
perfectly.

Just out of curiosity, is there a particular reason that the 
Userfunction you provided also implements the Serializable interface? I 
know the example user function implementation online just implements the 
Userfunction interface and not the Serializable one. When we make our 
own Userfunctions, is it good practice for us to implement Serializable 
as well?

Thanks again for the help!

- Eithon

Ernest Friedman-Hill wrote:

On Mar 14, 2007, at 8:40 PM, Eithon Cadag wrote:

Hi all,

Is binding a lambda function to a variable, and then using that 
function, possible in Jess?


You know, I don't think there *is* a way to do this. You can use the 
"map" function, but you'll get back the answer inside a list, which 
isn't terribly convenient. The "apply" function should be modified to 
handle lambdas as well as names. Here's a version of "apply" which 
does the right thing:

--------------------------------------------------------------
class Apply implements Userfunction, Serializable {
    public String getName() {
        return "apply";
    }

    public Value call(ValueVector vv, Context context) throws 
JessException {
        Userfunction uf = vv.get(1).functionValue(context);
    ValueVector args = new ValueVector();
    args.add(uf.getName());
        for (int i = 2; i < vv.size(); i++)
            args.add(vv.get(i));
        return uf.call(args, context);
    }
}
--------------------------------------------------------------

Then (apply ?fnc 2) would return "4".

---------------------------------------------------------
Ernest Friedman-Hill
Advanced Software Research          Phone: (925) 294-2154
Sandia National Labs                FAX:   (925) 294-2234
PO Box 969, MS 9012                 [EMAIL PROTECTED]
Livermore, CA 94550                 http://www.jessrules.com

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