Adds toEither :: a -> b? -> Either a b

[rjmk]

A function for converting a possibly null-y value to an Either
Closes #83

[davidchambers]

Very nice! I'll make several comments about minor issues, but they should all be easy to address. :)

[davidchambers]

Let's include an assertion for S.toEither('a', undefined).

[rjmk]

@davidchambers Do you prefer that I add commits separately during the review process and squash at the end, or just push up the amended commit as I fix?

[davidchambers]

I find mention of "'x'" and "'y'" a bit confusing. I think we could get away with referring to "the first argument" and "the second argument".

How about this?

Converts an arbitrary value to an Either: a Left if the value is null or undefined; a Right otherwise. The first argument specifies the value of the Left in the "failure" case.

I'd like to improve the descriptions of many of the library's functions. In many cases the description is just an English translation of the type signature. In this case, for example, a direct translation would be:

Returns a Left of its first argument if its second argument is null or undefined; a Right of its second argument otherwise.

I like the mention of a "failure value" in your description. I'd like to avoid mention of "'x'" and "'y'" though.

[rjmk]

Agreed! I'd modelled this after encaseEither, but I guess naming arguments is more important when some are functions

[davidchambers]

Do you prefer that I add commits separately during the review process and squash at the end, or just push up the amended commit as I fix?

I'm happy either way. Use whichever process works better for you.

[rjmk]

@davidchambers I think that's everything addressed

[davidchambers]

Thanks for the quick updates. I have three more requests:

• Please use single-quoted strings in the examples (sorry, the linter doesn't catch this).
• Let's drop the // from the protocol. location.protocol does not include the slashes, and the regexp literal will look less noisy without the \/\/.
• toMaybe is defined between fromMaybe and maybe. Let's move the definition of toEither to between fromEither and either.

[rjmk]

⚡

[davidchambers]

👍

[davidchambers]

Very nice patch, @rjmk. Thank you for tolerating my nitpicking. :)

🌳

[davidchambers]

$ npm install sanctuary@0.12.0

$ node
> const S = require('sanctuary')
undefined
> S.toEither
toEither :: a -> b -> Either a b