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From: Ralph Johnson <johnson@cs.uiuc.edu>
Date: Fri, 1 Sep 2017 11:35:28 -0500
Message-ID: <CAB_aMcsnijE0sWNX2gsqdPAcJFUpsgE=2vRpiL1yjwauqxddcw@mail.gmail.com>
Subject: recursive calls on Script object?
To: users@groovy.apache.org
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archived-at: Fri, 01 Sep 2017 16:35:35 -0000

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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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<div dir=3D"ltr">I&#39;ve been extending a system that is mainly in Groovy.=
 =C2=A0 It has a database that includes thousands of scripts, each of which=
 gets turned into a Script object.=C2=A0 Most are very small, but a few are=
 large.=C2=A0 Often one script calls another.=C2=A0 In fact, the call hiera=
rchy of scripts can get pretty deep.=C2=A0 There is nothing to prevent thes=
e scripts from being recursive, though I don&#39;t think any are.<div><br><=
/div><div>I ran into a problem where bindings were being reused inappropria=
tely, and it made me study Scripts in more detail. =C2=A0 It looks to me li=
ke a script that calls itself recursively will reuse the original binding.=
=C2=A0 That is because you set the binding with setBinding and then just us=
e the existing binding when you call evaluate(). =C2=A0 I would prefer a de=
sign 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.</div><div><br></div><div>Now, it is possi=
ble that recursion works fine on Scripts. =C2=A0 I haven&#39;t tested it.=
=C2=A0 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. =C2=A0 I couldn&#39;t find any documentation=
 that said anything about this.=C2=A0 I will do some experiments, but it wi=
ll be a lot of work because I have to change some things in our system befo=
re I can use it for the experiments.=C2=A0 So, I thought I would ask here f=
irst.</div><div><br></div><div>I tried cloning a Script. =C2=A0 I know that=
 compiling a Script creates a subclass of Script and the result is a unique=
 instance of that class. =C2=A0 I imagined that the instance held the bindi=
ng and used it as a delegate.=C2=A0 I figured we could clone the Script ins=
tance, set a new binding, and all would be well. =C2=A0 However, Scripts do=
n&#39;t seem to like to be cloned. =C2=A0 If Scripts don&#39;t like to call=
 themselves recursively, is there any way to make a copy so each call can b=
e to a unique instance?</div><div><br></div><div>-Ralph Johnson</div></div>

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