Rational Numbers: Add error test case to expreal property

[natanaelsirqueira]

As suggested by @jiegillet in gleam!248, we would like to add a failure edge case when doing the exponentiation of a real number to a rational number.

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[jiegillet]

(sorry I meant to send this days ago, but I forgot to click send, so it stayed pending)

[jiegillet]

This is kind of an edge case because a [1, 1] exponent is the same as doing nothing, and also the power -1 is not so interesting. If we want to test an actual case, maybe -8 ^ [1, 3] == -2 might be a better choice.
Same for the non-reduded case, it could be [2, 6] instead.

[natanaelsirqueira]

Hey! I tried using that example in my Gleam implementation but stumbled on this. This behaviour is the same in Elixir/Erlang. Any thoughts?

[jiegillet]

Yeah, that's a sensible choice. What I would do is check if the base is negative and the denominator odd, then take the power of the absolute value and negate it.

There is also the option of backing out of these strange cases altogether, although I kid of like them :)

[natanaelsirqueira]

Yeah... I'm up for dropping all of this tbh. It's starting to feel like we are overcomplicating the exercise and not adding much value. Plus, the initial motivation was to add an error case to our Gleam implementation because the function returns a result. Maybe we could just make that same check that float.power/2 does and have that be our error case?

[lpil]

Is this good to go? :)

[natanaelsirqueira]

@lpil Thank you for the reminder. In the interest of time, I believe it's reasonable to back out of this change to unblock the PR in the Gleam track. In hindsight, adding an error case to the problem spec solely because the Gleam function returns a Result may not be necessary. I'm open to being challenged on this, but if you agree with this approach, please feel free to leave your review/approval on that PR, and I'll proceed with closing this one.

[lpil]

Thank you. What do you think @jiegillet ?