Oh, I see what you mean now. No I would not pass that test. I'll modify the description to clarify that R will contain only unique pairs.

Yes that would be fine I think. But if I remember correctly in set theory the set [[1,1],[2,2],[2,2]] is equivalent to [[1,1],[2,2]]. R itself is also a set; a set of ordered pairs.

I have placed a blockquote for the readers convenience and changed the name philosophy to the title of the page where you land :). You are probably right that it is doubtful wheteher people will want to click/read the links.

I do intend to keep the excercise abstract as it is in fact a very abstract notion. To me that is part of the fun actually. Do you still have trouble opening the link (it is now beneath the blockquote)? For me its working both at home and at work.

Thanks. You have a good point. Instead of rephrasing I did some research to provide useful links to understand more about the topic.
Relations are an important concept in Logic/Math/Philosophy and a lot of more complex topics rely on ones knowledge of them. If the kata proves to be a success then I was planning on making a series out of it where people can learn a lot more about relations and at some point we can see some more interesting applications.

Thanks for your input Johan. From your reply I gather that my instructions were garbage :).

I have now rewritten the instructions to make it less abstract and added an image.

Let me know what you think.

Thanks for your feedback.
I changed it.

Could someone have a look at my clumsy solution and tell me why the first pattern test I do does not exclude white spaces? The other solutions seem very similar to my own but somehow do exclude the whitespace and so do not need the second check.

Thanks. Good point.

It seems to me that the errors generated by the tests have 'actual' and 'expected' mixed up. Kind of confusing :).