Hi Fused,
Nice to see more about ISL. I 've been playing around with a shader for wood and trying to work some of this out is trial and error.
Something that would be very useful is a description of the parameters passed into the eval() functions, and what is meant by the different types of coordinates (e.g. UV, ST, etc).
Also, for people not used to functional programming, a description of how to implement a loop with recursion might help. But I'm sure all of this and more is coming in the future tutorials!
Cheers,
gra.