Jess's "apply" differs from the classic Lisp "apply" in that the
varargs are in the "apply" funcall, rather than being bundled up in a
list. This is by accident rather than by design, I'm afraid. In
classic Lisp, this form
(apply str-cat "foo" " bar" " baz")
is an error, but in Jess, it's correct. In classic Lisp, you'd have
to say something like
(apply 'str-cat (list "foo" " bar" " baz")).
to get the same effect.
I think Steve Solomon wrote:
> Jess> (apply str-cat "foo" " bar" " baz")
> "foo bar baz"
Here there are three arguments to str-cat; each is converted into a
String, the strings concatenated, and the result is returned as a
String.
>
> Jess> (deffunction test ($?args) (apply str-cat ?args))
> Jess> (test "foo" " bar" " baz")
> "\"foo\" \" bar\" \" baz\""
Here, on the other hand, there is just one, the list in ?args. That
list is converted to a String, and that String is returned.
> To concatenate strings inside a function currently I use a foreach loop:
> (bind ?res "")
> (foreach ?str ?args (bind ?res (str-cat ?res ?str)))
> where ?args is the multifield parameter of the function as above.
Here's an (untested, but probably works) "apply*" function which acts
like classic Lisp "apply". Feel free to use it:
import jess.*;
public class ApplyStar implements Userfunction, Serializable {
public String getName() { return "apply*"; }
public Value call(ValueVector vv, Context c) {
Funcall f = new Funcall(vv.get(1).stringValue(c), c.getEngine());
ValueVector args = vv.get(2).listValue(c);
for (int i = 0; i < args.size(); i++)
f.arg(args.get(i));
return f.execute(c);
}
}
---------------------------------------------------------
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://herzberg.ca.sandia.gov
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