Ahh, thanks for the explainations guys. I knew what I was trying to get at.
I didn't realise C++ didn't like two part comparisions.

(And JulzMighty, I don't take it the wrong way. Anything helps me learn. )

I might give it another go when I've thought about it more. Maths is normally my strong point so I'm disappointed I forgot about the equal probabilities.

Edit: oh and the last line was supposed to be "a = b;" not "int b = a;.. I'll change the first post to suit.