Thanks - you have covered a fair bit of gorund here - I will modify myRange taking your suggestions into account. The one suggestion that I'm going to have to think through is repeatedly incrementing res.
I deliberately did not use this as repeated addition can cause rounding errors to accumulate, making the loop run a little longer or shorter than necessary. I thought I would be far less likely to run into rounding issues with a multiplicative construct - hence my use of epsilon, and my question about an appropriate value for it -- http://mail.python.org/mailman/listinfo/python-list
