Try Python ;)

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Please do Kata for programing, not for English.
It is not spoiling to see error messages.

Ye, it's a good note) I have forgotten about it)

Ah, I see. I would recommend incorporating the "returns an integer" into that first sentence; it's all a bit wordy, and as I was familiar with the concept (and thought it usually works with strings), I kinda skimmed that wall of text at the top. So it's my fault, but it could be eased nonetheless.

I would recommend those backticks, yes. They are a great way of setting text/code/values apart from the description without confusing people with actual code-like text (quotes, etc).

You're right, I'll do that

It does require a little more mathematical background than some other kata, but being able to translate mathematical concepts into code is an important programming skill. If someone understands basic algebra, they can understand the derivative well enough to complete this kata just by poking around wikipedia.

Yes. The codewars ranking system does not apply very well to this problem because in order to solve it, one is required to know more about math than they are required to know about programming.

Got it. Insight much appreciated.

Ok, rather than rewrite the kata, I just updated the instructions to reflect that, in this case, only integers are acceptable. Also included a method to convert negatives to positive and drop any decimals. Added additional Test.assertEquals() for negatives and zeros, and will use those Test methods going forward. Thanks.

Yeah-- that's right. Thanks for your help!

Given that expression is in postfix notation I don't think eval() makes big difference.

indeed, my next secret message kata is random

Thanks for your suggestions. It's my first authored kata. Question: If I update the function so it only accepts positive integers, would it break the attempts submitted by other members, or rather, make them invalid?