Non-empty strings & various operations

[garyb]

Kinda depends on #99, since I continued after that.

Alternative to #98 that keeps the underlying representation as just being a plain String, and adds functions and tests for all the usual stuff.

[safareli]

fromString returns Maybe NonEmptyString so here I guess should be unsafeFromString or something like that.

[garyb]

Hmm, yeah I guess so. I didn't want to add that originally as the unsafeFromString I had in mind was really unsafe, but I guess if we do it as fromJust <<< ... and give it the Partial constraint that'll work well enough.

[safareli]

btw where do you think this should leave?

class IsSymbolNonEmpty sym where
  safeStr :: SProxy sym -> NonEmptyString

instance isSymbolNonEmpty :: (IsSymbol s, Equals s "" False) => IsSymbolNonEmpty s where
  safeStr _ = asNonEmpty $ reflectSymbol (SProxy :: SProxy s)
    where
    asNonEmpty :: String -> NonEmptyString
    asNonEmpty = unsafeCoerce

[garyb]

For now, not in here. The compiler solved classes are going to be moved around a bit in 0.12, so after that we can consider including it in here perhaps :)

[hdgarrood]

Can I just say pre-emptively, I'm not a big fan of the name "safe", since it implies possibly-empty strings / String types which are inhabited by an empty string are "unsafe", which I don't think really makes sense as a claim; often you do want or even need to include the empty string in your consideration. It's just that having more specific types is sometimes (not always) more appropriate. I think a more appropriate name would be reflectNonEmptySymbol or reflectNonEmpty, to mirror reflectSymbol.

[garyb]

Yeah, that sounds perfectly reasonable. Any thoughts on the rest of this @hdgarrood? (No need to review fully if you don't have the time)

[hdgarrood]

I've only looked over it briefly but it all looks good to me 👍