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Re: calling scheme procedure from java and passing a list as argument...
- From: Damien Mattei <damien dot mattei at unice dot fr>
- To: kawa at sourceware dot org
- Date: Fri, 18 Sep 2015 15:51:16 +0200
- Subject: Re: calling scheme procedure from java and passing a list as argument...
- Authentication-results: sourceware.org; auth=none
- References: <55FABBA1 dot 4080106 at unice dot fr> <55FB0C6E dot 3060506 at bothner dot com> <55FBDEF8 dot 4040707 at unice dot fr>
finally i understand my error,result of many years without coding in java...
here is the solution:
LList glst = new LList();
//glst = glst.list2(2,3); // works also
glst = LList.list2(2,3);
System.out.println("glst : "+glst);
Object result0 = vec.plus(glst);
System.out.println("result0 :"+result0);
Pair pair = new Pair(2, LList.Empty);
Pair pair2 = new Pair(3, pair);
LList glst2 = new LList();
glst2 = pair2;
System.out.println("glst2 : "+glst2);
Object result = vec.plus(glst2);
System.out.println("result : "+result);
and the result:
glst : (2 3)
result0 :5
glst2 : (3 2)
result : 5
Le 18/09/2015 11:52, Damien Mattei a Ãcrit :
>
> Le 17/09/2015 20:54, Per Bothner a Ãcrit :
>>
>> On 09/17/2015 06:09 AM, Damien Mattei wrote:
>>> hello again,
>>> suppose i have a java code (the case is running on tomcat web server but
>>> that's make no difference)
>>> and i want to pass a list to a scheme routine, i have two questions:
>>> -is there a way to call a scheme procedure in kawa,i suppose the answer
>>> is yes but how?
>>> ( i know i can do it making a method in a kawa class definition and call
>>> the method)
>> This page talks about *evaluating* Scheme from Java:
>>
>> http://www.gnu.org/software/kawa/Evaluating-Scheme-expressions-from-Java.html
>>
>>
>> If you have a Scheme Proecdure object you can call by using one of the
>> apply methods. For example:
>>
>> Object[] args = {x, y};
>> Object result = myProc.applyN(args);
>> or:
>> Object result = myProc.apply2(x, y);
>>
>>> - but how can i pass a list as parameter, what is the equivalent of
>>> scheme list in java or kawa??
>>> I would greatly appre"ciate a little example...
>> To create a list you can use one of the static methods in
>> gnu..lists.LList,
>> like makeList or list1 ... list4.
>>
>> It's usually best to do as much as you can in Scheme: It is easier (and
>> better documented with a more stable API) calling Java from Scheme
>> than calling Scheme from Java.
> unfortunalely this is a java project including scheme,not the reverse,
> i tried to use list2 in this example but it complains that
> gnu.lists.LList is not a pair,
> in scheme a list is a pair.
> i have this error:
> Exception in thread "main" Argument #1 '(. #<not a pair>)' to 'car' has
> wrong type (gnu.lists.LList) (gnu.lists.LList cannot be cast to
> gnu.lists.Pair)
> at Vector2D.plus(Vector2D.scm:28)
> at helloworld.main(helloworld.java:30)
> Caused by: java.lang.ClassCastException: gnu.lists.LList cannot be cast
> to gnu.lists.Pair
> ... 2 more
> when i try to run this code:
>
> LList glst = new LList();
> glst.list2(2,3);
> Object result = vec.plus(glst);
>
> on this method definition in Vector2D class:
> ((plus L) ::int
> (+ (car L) (cadr L)))
>
> this is of course for testing before doing serious work...
>
>
>
>