Limits and the system of near-numbers

(http://arxiv.org/abs/math/0412157)
I am in ecstasies.

This is how first-semester calculus ought to be taught.

My one complaint is that the list of references is incomplete. It doesn't reference, for example, Abraham Robinson's infinitesimals. I think there are intuitionists who work with intervals in formalizing a rigorous and constructive theory of calculus and analysis, but I can't find a good reference in a few google searches.

I highly recommend this paper.