Add support for trim option to String.split and Regex.split

[vanstee]

To support the trim option I had to reimplement split to remove all empty strings from the result.

Here's an example:

iex> String.split(" a b c ", " ", trim: false)
["", "a", "b", "c", ""]
iex> String.split(" a b c ", " ", trim: true)
["a", "b", "c"]

[rafacv]

Hi @vanstee,
String.split has a very strict purpose; IMO adding trim option to it would not only add complexity as also blur its definition. I'd rather implement String.trim to use in support of String.split to achieve the desired outcome.

Going beyond, I think global argument in String.split is pretty bland. A limit option that enables you to choose how many iterations to be performed would be much more useful. It's matter for another PR though.

Please, take into account that I'm completely unaware of any context to this Pull Request so my opinion might be wrong and I reserve my right to change my mind later. 😄

[josevalim]

@vanstee Why did you have to reimplement it? Couldn't you simply filter the results afterwards? :)

[vanstee]

@josevalim That's a way better idea. I think I got a little carried away :P

[josevalim]

@vanstee ok, let me know when you change it and i will merge it right away :)

[vanstee]

@rafacv Oh I should have linked to the previous issue for some more context: #1645

Since :binary.split supports trim, it seemed fitting to add it to String.split. I don't have a strong opinion about global but I know Regex.split has a parts option similar to your limit idea. I think both of these are copying the options available in Erlang.

[vanstee]

Ahh... So much nicer with less code :) Thanks for the suggestion @josevalim!