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POLisp code called from Java
 

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    <p>Long story:</p> <p>I am doing a project for my functional programing class, and I thought of writing an AI controller in Lisp, for the <a href="http://julian.togelius.com/mariocompetition2009/" rel="noreferrer">Mario AI competition</a>.</p> <p>I was looking over frameworks/libraries/ways of calling Lisp code from Java, or even better Lisp-Java intercommunication. </p> <p>I have looked at <a href="http://jacol.sourceforge.net/" rel="noreferrer">Jacol</a>, but it is old, and it does not compile fine for me. </p> <p>My best choice so far is: <a href="http://jatha.sourceforge.net/" rel="noreferrer">Jatha</a>. It is really neat, although some lisp constructs are not yet implemented, one can easily define his own constructs. For example <strong>mapcar</strong> and <strong>cond</strong> are not implemented. I have implemented my own <strong>mapcar</strong>, named <strong>mapp</strong> in Lisp like this:</p> <pre><code>(defun map* (f l r) (if (null l) r (map* f (rest l) (cons (funcall f (first l)) r)))) (defun mapp (f l) (reverse (map* f l nil))) </code></pre> <p>Now I have a simple function that uses this, for example, a function that numbers how many atoms there are in a non-linear list</p> <pre><code>(defun myfunc (l) (if (atom l) '1 (apply '+ (mapp 'myfunc l)))) (myfunc '(6 2)) </code></pre> <p>This all works fine in <strong>clisp</strong> Now to call Lisp code from Java I used <strong>Jatha</strong>. All one has to do is import the Jatha library in the java project and load a lisp file like this (ex):</p> <pre><code>import org.jatha.*; import org.jatha.dynatype.*; public class Main { public static void main(String[] args) { Jatha lisp = new Jatha(false, false); lisp.init(); lisp.start(); LispValue file = lisp.makeString("X:\\lispproject\\test1.lisp"); LispValue rez1 = lisp.load(file); } } </code></pre> <p>While that code works fine in clisp, and other implementations, this code produces a StackOverflow</p> <p><code> run: APPLY: fn = +, args = ((1 1)) S: ((+ (QUOTE 1) (QUOTE 1))) Exception in thread "main" java.lang.StackOverflowError at java.lang.Long.toString(Long.java:242) at java.lang.Long.toString(Long.java:100) at java.lang.String.valueOf(String.java:2946) at org.jatha.dynatype.StandardLispInteger.toString(StandardLispInteger.java:113) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:152) at org.jatha.dynatype.StandardLispCons.toStringAsCdr_internal(StandardLispCons.java:174) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:153) at org.jatha.dynatype.StandardLispCons.toStringAsCdr_internal(StandardLispCons.java:174) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:153) at org.jatha.dynatype.StandardLispCons.toStringAsCdr_internal(StandardLispCons.java:174) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:153) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:152) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:152) at org.jatha.dynatype.StandardLispCons.toStringAsCdr_internal(StandardLispCons.java:174) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:153) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:152) at org.jatha.dynatype.StandardLispCons.toStringAsCdr_internal(StandardLispCons.java:174) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:153) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:152) at org.jatha.dynatype.StandardLispCons.toStringAsCdr_internal(StandardLispCons.java:174) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:153) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:152) at org.jatha.dynatype.StandardLispCons.toStringAsCdr_internal(StandardLispCons.java:174) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:153) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:152) at org.jatha.dynatype.StandardLispCons.toStringAsCdr_internal(StandardLispCons.java:174) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:153) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:152) at org.jatha.dynatype.StandardLispCons.toStringAsCdr_internal(StandardLispCons.java:174) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:153) at org.jatha.dynatype.StandardLispCons.toString(StandardLispCons.java:152) at org.jatha.dynatype.StandardLispCons.toStringAsCdr_internal(StandardLispCons.java:17 </code></p> <p>So my question is, why does it do this? Is my code wrong? <br/> Is it a bug in Jatha? See for yourself, it doesn't take long to set up. <br/> Have you ever done something similar?<br/> Do you know any other better ways to do this? All I want is to call from Java some Lisp code, get it executed, and get back results computed by the Lisp code. <br/> Thanks.</p> <p>[Edit] Fixed code, pasted something wrong.</p>
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    1. COGenerally go for pure Java solutions, not Java with calls to native code. Your life will be happier :) In this case, a LISP running on theJVM.
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      1. USThorbjørn Ravn Andersen
 

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