[eigen] Operations involving constants

[oz <dwwork@xxxxxxxxx>]

So I'm working on my own little test class to learn expression 
templates, etc. and have run into a bit of a snag.
I'd appreciate any help in understanding. I'm uncertain how to implement 
the following kinds expressions:

2*array
array+1

It looks like Eigen somehow implements this in the Unary Operators, 
which makes sense, but I can't figure it out.

I tried encapsulating the constant into a Constant<T> class, and using 
the BinaryOps like normal, but that gave me segfaults for some reason.
How would y'all suggest I approach this issue?

Thanks for the help.

Dalon