Eric, Guillaume, Thanks for the info, I think the solution is partly simple, partly complex. Firstly it is now clear to me (as stated in the documentation) that max(interval_a,interval_b) is not std::max. The difference in semantics is however only represented by the difference in return value. The new std_max/ std_min should ONLY be used as a -- ___________________________________ Michael Stevens Systems Engineering 34128 Kassel, Germany Phone/Fax: +49 561 5218038 Navigation Systems, Estimation and Bayesian Filtering http://www.sf.net/Bayes++ ___________________________________