[crashandburn4]

I was finding it hard to understand why it wasn't differentiable (guess my maths is getting a bit rusty) until I read the below[0] which helped it make sense to me:

>The function has detail at every level, so zooming in on a piece of the curve does not show it getting progressively closer and closer to a straight line. Rather between any two points no matter how close, the function will not be monotone.

[0] http://en.wikipedia.org/wiki/Weierstrass_function

[gballan]

Good point, thanks. I added the quote from wikipedia, and moved the link from the CoffeeScript to the HTML.

[gohrt]

Also note that your code is for a differentiable finite approximation, unless you implement unlimited zoom.