Fix implementation of isEmpty and overlaps in Interval.hs

[norman-thomas]

A fellow Plutus Pioneer Program student (BC Chuah) noticed an odd behavior of the overlaps function.

Upon further investigation, I noticed that both overlaps and isEmpty needed a change to work as expected.

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[j-mueller]

The implementation looks ok now, thank you.

You could add some property tests for this to plutus-ledger/test/Spec.hs as well. For example, every non-empty interval overlaps with itself. There are some examples already.

[j-mueller]

Oops!

[norman-thomas]

Sure, I already started implementing basic test cases, e.g.
norman-thomas@ff495db

Am currently familiarizing myself more with Haskell and (property based) testing in Haskell before daring to submit those.
I will follow up shortly with the tests.

Thanks for the example and pointing me in the direction!

[norman-thomas]

@j-mueller

I added a couple of test cases covering isEmpty, overlaps and intersection.

Sadly, the Hydra CI check fails, but it seems to be failing in master as well.

[michaelpj]

Flaky VM test, restarted.

[j-mueller]

Great, thanks for adding the tests.