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Add genBoundedEnum #29

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merged 3 commits into from
Jun 8, 2017
Merged

Add genBoundedEnum #29

merged 3 commits into from
Jun 8, 2017

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garyb
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@garyb garyb commented Jun 8, 2017

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@garyb garyb mentioned this pull request Jun 8, 2017
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paf31 reviewed Jun 8, 2017
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src/Data/Enum/Gen.purs Outdated
-- | `fromEnum bottom` and `fromEnum top`.
genBoundedEnum :: forall m a. MonadGen m => BoundedEnum a => m a
genBoundedEnum =
unsafePartial fromJust <<< toEnum
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This unsafePartial is only safe if the Enum instance is valid, I think.

Another option is oneOf (bottom .. top), or something along those lines, right?

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This generator I lifted from QuickCheck actually, it was recently added there, so it suffers from any of the same problems that that one has.

Can you explain what you're thinking with oneOf (bottom .. top), I'm not sure I follow?

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It does say in the comment that toEnum must be well behaved too 😉

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@paf31 paf31 Jun 8, 2017 •
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By bottom .. top, I meant to say enumFromTo bottom top, which must be safe, I think.

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Ahh yeah, that'd work. It'll be kinda expensive if used for large enums, but can revisit if we have a case where it's obviously terrible. :)

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garyb commented Jun 8, 2017

How's this? A slight bias to bottom now, but necessary without adding dependencies or FFI something, since there's no array/list dependency even transitively.

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paf31 commented Jun 8, 2017

👍 Thanks!

@garyb garyb merged commit d307db5 into master Jun 8, 2017
@garyb garyb deleted the gen branch June 8, 2017 20:27
hdgarrood pushed a commit that referenced this pull request Jul 29, 2017
@garyb @hdgarrood
Add genBoundedEnum (#29)
7903b52 
* Add `genBoundedEnum`

* Use `enumFromTo` for `genBoundedEnum`

* Un-bias the enum generator
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