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Cycles in family tree software Asked 12 years, 7 months ago Modified 8 years, 5 months ago Viewed 286k times 1590 votes Locked. This question and its answers are locked because the question is off-topic but has historical significance. It is not currently accepting new answers or interactions. I am the developer of some family tree software (written in C and Qt). I had no problems until one of my customers mailed me a bug report. The problem is that the customer has two children with their own daughter, and, as a result, he can’t use my software because of errors. Those errors are the result of my various assertions and invariants about the family graph being processed (for example, after walking a cycle, the program states that X can’t be both father and grandfather of Y). How can I resolve those errors without removing all data assertions? C graph cycle assertions family-tree