Took me a while looking through the Array docs to find product, I was trying hacky ways with permutation before that.

This code is better than my own though!

Use chars instead of split(//). It's several times faster and (IMO) more readable

that line is so long it hurts my eyes

Thanks for your comments. I fixed the first two issues—thanks for catching them!

There are plenty of situations where having this in a separate class would be useful: you may want to initialize an instance once with an unknown parameter and then use that same instance a number of different times throughout your application, without having to specify unknown again.

You could compare it to Redcarpet's API, e.g. (taken from its Readme):

# Initializes a Markdown parser
markdown = Redcarpet::Markdown.new(renderer, extensions = {})

markdown.render("This is *bongos*, indeed.")
# => "<p>This is <em>bongos</em>, indeed.</p>"

What would you have done instead?

The method names in the description mismatch those in the skeleton code. Also, the method #transcode_char has a parameter in the skeleton code which is misleading / not required. Moreover, why does this transcoder need to be a seperate class?

Clever solution. I wish I knew product method before.

This is not correct, as I had the exact same solution to start with. When given 100, this will return ",100".

Can we help to improve katas with better tests so errors like this (and I noticed a few) will not pass? And ... make sure that better test-suites are re-run against entered solutions?

This gets an upvote for best practice, but the solution is just plain wrong.

Damn it, submitted to early :D
remove output

Using it and works like a charm... What was it that frustrated you?

If no initial value is given, this implementation does however change the originating array since '#shift' deletes the first value from the array.

So, handle with care ;)

Same here, either some tests or an more ellaborate description of the Kata would be helpful.