Goodness. See the sci.math FAQ (sorry, you'll have to paste this together again): <http://www.cs.unb.ca/~alopez-o/math-faq/node40.html#SECTION0053000000000000 0000> Knuth is in good company with Euler and Kahan on this one <wink>. practicality-beats-purity-ly y'rs - tim