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#2No Eq/Ord/Read/Show instances for IntervalMap or PriorityQueue?

Zemyla

IntervalMap and PriorityQueue don't have Eq, Ord, Read, or Show instances, and IntervalMap has no toList method that would make implementing such an instance possible. PriorityQueue could have a toList method hacked together with unfoldr minViewWithKey, but a native toList method would be much more efficient.

• Ertugrul SöylemezSun Apr 17 21:38:55 UTC 2016

  Both are Foldable, so use toList from Data.Foldable.

• ZemylaSun May 15 15:31:32 UTC 2016

  The toList from Foldable only gets the values, not their associated intervals.

• Ross PatersonMon Jul 25 18:16:15 UTC 2016

  added Eq, Ord and Show instances for these two. The instances for PriorityQueue use unfoldr minViewWithKey, because they have to be done in key order to be meaningful.

• treeowlTue Nov 3 07:40:46 UTC 2020

  I have grave doubts about the Eq instance for priority queues. Do the other operations actually respect this equality? Which copy of a key we get, and therefore which value, when we extract the minimum is sensitive to tree balance. I don't think there's a really valid Eq instance available for this type. If you squint your eyes and don't care which values you get in which order, then I think you at least get a meaningful equivalence (not implemented by this instance), but it really doesn't feel like == to me.

• treeowlWed Nov 4 07:32:49 UTC 2020

  Ugh... Please ignore my ignorant comment