Wow. Very clever. I know pretty much nothing about binary (currently working on changing that), so I guess that explains why I didn't understand it. It's really incredible how much I've learned new skills and refined old skills thanks to this site and its knowledgeable users. Looking forward to learning more, thanks so much for the help!

As alpardel said it's the left bitwise shift operator if applied to a Number

If you take an integer 11 which is 1011 in binary and shift the bits 1 to the left you get 10110 = 22
if you shift them 2 to the left you get 101100 = 44

It's a left-shift bit operator: x << n shifts the bits of 'x' n position to the left, doubling its value once for each shift. E.g.: 3 << 2 = 3 * 2 * 2 = 12

http://en.wikipedia.org/wiki/Bitwise_operation#Bit_shifts

I thought "<<" only adds things to a hash/array. What is its function here?

I up voted it as Clever - by way of an apology

Yeah, sorry - I saw that after my comment (see my EDIT) :)

Don't know how I misread it!!

"My" description says (Assumptions):

• You **CAN** assume that you are **only given numbers**.
  

• You cannot assume the size of the array.
  

• ...

This is a 4 kyu kata. If you are completely stuck, perhaps you should consider doing some of the katas closer to your current kyu.
If you still wish to proceed, then read the description carefully. It tells you how to extract the arguments from a function.

It would be nice if someone would respond to my plea for help!

Help please I'm stuck on this, I have it working for all test cases where the function params are (a, b) - because I define my returned function as

return function (a, b) {

But when the params are (x, y) for example it fails unless I change it to return function (x, y) { - I cannot work out how to abstract the returned function parameters

I can post my solution if necessary

loved this one, some really cool solutions out there

finally got there!