https://golang.org/pkg/reflect/#DeepEqual
"Pointer values are deeply equal if they are equal using Go's == operator or if they point to deeply equal values." By the rules described here, the fact that both pointers have the same value means it does not even NEED to check what they point to, so I don't think it ever even sees the cycle. So yeah, you would have to write your own implementation, or find one. https://github.com/google/go-cmp is an example of a custom DeepEqual implementation that allows overriding of the comparison basis by implementing an interface (it was designed for equality testing in tests). >From a programmatic perspective, there are two basic ways of comparing two objects for equality - you either walk both objects, returning false the first time you find a mismatch; or you render both objects into a more directly comparable form, and then compare those. For objects that contain directed or cyclic graphs, going the latter route (which *must* include cycle-breaking to avoid infinite loops) provides the opportunity of applying a 'canonicalization' pass on the intermediate form before the comparison. As an example, if you had two List pointers of the sort you used in your example, that *did* have the same structure, they would be unequal under DeepEqual (if they carried any comparable, non-equal information *aside* from the next pointer), but if canonicalized in a consistent manner that rotated each cycle to have the same starting point in a resulting acyclic graph subsequent to cycle-breaking, could then be compared equal. This requires general graph manipulations, though, and could greatly increase the cost to compare on complicated objects. (After all, it is effectively the same as asking whether two mathematical objects share the same topology, and that is the sort of question that can provide someone a PHD thesis!) But while a *general* solution may be quite expensive, for a specific case where you have control over the objects, it could be as simple as always walking a list until you find the node marked with a head flag before comparing them. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
