Alfonso Acosta
2) An implementation of type-level Naturals would really help. What has already been done?
I see you have received many suggestions already and personally I don't think you can go wrong with Oleg (et al)'s implementations. For a decimal representation you probably don't have much choice anyway! For completeness let me mention that an unadvertised part of the Dimensional[1] library is an implementation of type-level unary Integers[2] (as opposed to Naturals). Addition, subtraction, multiplication and division is supported. As I side note I've spent quite some time experimenting with fixed-size vectors and matrices with heterogeneous elements. For this I've been using Oleg, Ralf and Keean's HList[3] library which also has type-level unary Naturals. -Bjorn [1] http://dimensional.googlecode.com [2] http://www.buckwalter.se/~bjorn/darcs/dimensional/Numeric/NumType.lhs [3] http://homepages.cwi.nl/~ralf/HList/