Henning Thielemann wrote:

I've attached a Haskell module demonstrating the beauty of solving ordinary differential equations in terms of power series. A power series is expressed by the (infinite) list of its coefficients. What do you think about that?

Sorry for shameless personal plugin, but, please, check out my old paper: http://users.info.unicaen.fr/~karczma/arpap/lazysem.ps (published in Theor. Comp. Sci. some centuries ago). You should perhaps see also the paper of Doug McIlroy, who cooked-up some algorithms quite similar to mine, independently, and published a Functional Pearl in JFP. There is an another piece of my stuff, where there is something about the dif- ferential equations here: http://users.info.unicaen.fr/~karczma/arpap/laseq.pdf Jerzy Karczmarczuk