The OP found an answer to their question.

Fixed.

the list monad bind operation will only work iff the given function also returns a list. the author's intention was to make sure an error is thrown in these cases, to make sure no invalid result is produced.

Was also a lot less work than the 1kyu and 2kyu ones I did; solution is quite small even. Thinking wise it's a bit you'll have to chew through, but I guess the same applies to the harder problems if you don't happen to be familiar with the area yet.

The old API supports it: http://www.codewars.com/users/tansaku.json. You should be fine to use that for now, I'll add it to the list to add to the http://www.codewars.com/api/v1/users/tansaku.json version, which will eventually supersede the non-versioned API.

Ahh, I was so bummed to find out that you couldn't do this!! Please Codewars make this happen!

Your left associative parser was the correct one.

i think this one was rather easy. much easier than several 4kyu kata such as LRU cache and List monad for example

Disabling 'eval' doesn't disable Kernel#eval.

Try this link: http://www.codewars.com/kata/evaluate-mathematical-expression/edit/ruby
Does it work for you?

You CAN edit directly. It used to be a bug that contributors did not have edit link, but now you should see it.

In addition, the C# version should say the requirement is to throw an ArgumentException under these conditions.

yes-ish... it is not about "a double or a non-double" but about "just one double or nothing".

a Maybe Double differs from a Double.
a Maybe a is like a list of as with at most one element.

let me hoogle that for you... https://www.haskell.org/hoogle/?hoogle=Maybe

From what I can see in your profile, you only solved one 6 kyu and one 5 kyu katas recently. Of course this will not be noticeable from single low-level katas! Try solving a pack of these, I think you'll see some small progress.

Glad we came to some common understanding. And thank you, this was an interesting discussion, I've learnt something new from you.