I saw a similar error using Javascript. I had an error in my code that had nothing to do with JSON. I fixed the error and everything worked.

Great kata. Worthly of it's rank.

I liked this kata a lot. The introduction is spare, but I thought the requirement was clear from the context of the example. It took longer than I'd want to admit, but it was satifying and instructive to arrive at a simple solution to a simple problem. Thanks for offering another excellent kata!

I was confused about the format of the answer. I thought you were looking for a string of comma separated results, or perhaps separated by newline. In fact, the answer is supposed to be an array of strings.

Elegant, satisfying kata!

It worked correctly when I reset. Thanks again!

Thanks for letting me know. I wonder if a whitespace is being added at the beginning. When I run the test, there is a space in the code in the line following "Your code:". You might consider trimming leading and following whitespace. Thanks for your response and for the challenging kata.

I retyped it in directly, and got the same result.

Tough but fair ;)

I like how you did the compose function. I used recursion, but yours is cleaner.

Outstanding kata, both in grappling with monads and in delving into how to use arguments in a more sophisticated way. The functional way of thinking has changed how I code.

Thanks for clarifying that point for me, and for your huge contribution of katas. I assume the alternative would be <= ordering, which would allow duplicates. Does this notation come from the mathematics of sequences or from computer science? I tried looking it up but couldn't find it.