ClassCastException (class java.lang.Integer cannot be cast to class gnu.math.IntNum)

[Zachary Kurmas <kurmasz@gvsu.edu>]

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Does anybody recognize this exception:

java.lang.ClassCastException: class java.lang.Integer cannot be cast to class gnu.math.IntNum (java.lang.Integer is in module java.base of loader 'bootstrap'; gnu.math.IntNum is in unnamed module of loader 'app')

I apologize for the overly vague question, but I can’t seem to come with a minimum example, so I was hoping someone had seen the error before and could point me in a useful direction.

If you are curious, here is an example of why I’m having trouble isolating the source of the error.

  *   I am having my students write Connect 4 in Kawa.  Only one student has run into this problem.
  *   The basic structure of the project is that
     *    (1) connect4.scm parses the command line (which is mostly code I wrote)
     *    (2) connect4_engine.scm has the students’ code.
  *   My code parses the command line, calls include-relative on the “engine” code then calls the function play-connect-4
  *   I see the bug when running connect4.scm — even if I hard-code all the parameters to play-connect-4.
  *   I don’t see the bug if I copy the call to play-connect-4 (with hard-coded parameters) to the end of connect4_engine.scm and run that file directly.

So, trying to isolate the bug makes it go away.  Also, when connect4.scm calls connet4_engine.scm the stack trace does not contain line numbers of connect4_engine, so I don’t have a good sense of where the bug is popping up.


Thanks,
Zack

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Zachary Kurmas
Associate Professor of Computer Science
Grand Valley State University
https://kurmasgvsu.github.io