How to debug blocking programs

Torsten Anders torsten.anders at
Thu Jun 7 18:48:53 CEST 2012

Dear fellow Oz programmers,

I guess that it already happened to many of you that your program blocks without any error message (e.g., the program performs some operation on a free variable and just waits for more information to be bound to that variable before it can continue). This ability is clearly a strength of the language.

On the other hand, accidental blocks are also particularly frustrating bugs for the programmer, because the language gives no feedback about the cause of the problem. I often have spend hours identifying some trivial cause, because it took so long to isolate the bug. Quite likely, this is the single kind of bug on which I spend by far most time fixing them.

Question: what are your strategies for fixing blocking programs? Thanks a lot! 

Best wishes,

Dr Torsten Anders
Course Leader, Music Technology
University of Bedfordshire
Park Square, Room A315

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