Store.unfold, List.iterate, Stream.iterate about base HOT 9 CLOSED

Merged in base hash #p47o3ehssr 🌈🌟

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Cool! I probably won't get to take a closer look at this until next week and @runarorama is also out.

One thing I noticed: I don't think there should be any patch updates with this PR. The name Abort.toOptional was repurposed but the old definition is still valid, and I think the definition is now called Abort.toOptional!. Me or @runarorama can fix up the PR though, the functionality looks great!

The workflow for this needs improvement and is being tracked here unisonweb/unison#2248 since it's pretty error prone. One tip is you can do update .trash to send updates to a dummy patch that you delete occasionally.

https://www.unisonweb.org/2020/04/10/reducing-churn/ is a good post for more reading on this.

Here's another List function we noticed was missing that would be a good addition, if you want to take a crack at it!

List.find : (a ->{g} Boolean) -> [a] ->{g} Optional a
List.find! : (a ->{g} Boolean) -> [a] ->{g, Abort} a

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Having thought about it more, I think iterate ought to return a stream, not a list, and should not require the passed function to decide when to stop. That should be the responsibility of the caller, using something like take or takewhile. In Haskell iterate returns a lazy infinite list, and I was confused since Haskell collapses the distinction between the two.

This only really occurred to me when I started coming up with examples and the passed functions were always something like

if n > 10 then abort else n + 1

Which is extremely not composable.

I'm not sure whether unfold ought to as well, as in this case the provided function is supposed to be responsible for stopping, and the output will often in fact be finite. I guess it can't hurt to have both versions of both functions? Thoughts?

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Here's another List function we noticed was missing that would be a good addition, if you want to take a crack at it!

For sure, I also have List.deleteFirst : (a -> Boolean) -> [a] -> [a], which I could generalize and add

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@sullyj3 You'll also want to add aliases for your Author and License metadata to the metadata.authors and metadata.licenses namespaces, respectively. e.g., alias.term sullyj3 .prs.base.unfoldStore.metadata.authors.sullyj.

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Ah yep, do I also need to alias my CopyrightHolder and GUID?

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Updated with just Author and License for now

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Ah yep, do I also need to alias my CopyrightHolder and GUID?

Yep, mirror the structure of one of the existing authors. I think it's just a couple copy.namespace commands at this point.

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Righto cool. Updated with the additional metadata as well as Stream.iterate

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