This kinda defeats the purpose, but still the right call nonetheless

155+ general obviouses.

This does not preseve whitespace.
" this is wrong" should arguably still include a leading space (as said by babakgh)
"this [space space space] is wrong" should arguably still have multiple spaces between 'this' and 'is'
EDIT: Aparently codewars also doesnt preserve multiple whitespace even in code blocks, but hopefully its clear what I mean

Fails with this " this is wrong "

test this:

I say "go"

It won't work

it's a very neat and idiomatic code but as the pattern you capitalize is defined in split, it is not robust nor flexible at all.

wow. great job on this.

Then you displays a validation error until the user types without any errors.

what if space symbol is missed by a mistake, like: "No body really cares,what are you thinking about."

Are "Best Practices" just the top Google result for a properly asked question? [serious]

Oops. Thanks xcthulhu!

Hmmm... yeah... that's a typo. I've gone ahead and fixed it for the author. Does it make more sense now?

I mean, why 12345 becomes [2, 2, 2, 3, 2]?

You have to go through and double every other digit...

Great kata. I added 500 test cases to the haskell fixture from http://www.getcreditcardnumbers.com/ , so I am really confident that it's impossible to cheat now...