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From Ralph Johnson <john...@cs.uiuc.edu>
Subject recursive calls on Script object?
Date Fri, 01 Sep 2017 16:35:28 GMT
I've been extending a system that is mainly in Groovy.   It has a database
that includes thousands of scripts, each of which gets turned into a Script
object.  Most are very small, but a few are large.  Often one script calls
another.  In fact, the call hierarchy of scripts can get pretty deep.
There is nothing to prevent these scripts from being recursive, though I
don't think any are.

I ran into a problem where bindings were being reused inappropriately, and
it made me study Scripts in more detail.   It looks to me like a script
that calls itself recursively will reuse the original binding.  That is
because you set the binding with setBinding and then just use the existing
binding when you call evaluate().   I would prefer a design in which you
would pass in the binding to evaluate() so that a script could call itself
recursively or you could have two concurrent evaluations of a script in
different threads.

Now, it is possible that recursion works fine on Scripts.   I haven't
tested it.  Perhaps the execution of a Script clones the relevant info
including the binding and changing the binding during the execution of a
Script will have no effect on the Script.   I couldn't find any
documentation that said anything about this.  I will do some experiments,
but it will be a lot of work because I have to change some things in our
system before I can use it for the experiments.  So, I thought I would ask
here first.

I tried cloning a Script.   I know that compiling a Script creates a
subclass of Script and the result is a unique instance of that class.   I
imagined that the instance held the binding and used it as a delegate.  I
figured we could clone the Script instance, set a new binding, and all
would be well.   However, Scripts don't seem to like to be cloned.   If
Scripts don't like to call themselves recursively, is there any way to make
a copy so each call can be to a unique instance?

-Ralph Johnson

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