In boost::random the random number generators #include <iostream> This introduces the unnecessary definitions of the standard stream cin, cout etc. These are not required to define the stream operations and will fail on runtime environments which cannot define the default streams. It would be better to use instead: #include <istream> #include <ostream> On indeed only the forward definition are required to define stream operations #include <iosfwd> The latter requires that when the templates are instantiated a stream definition exists. Michael -- ___________________________________ Michael Stevens Systems Engineering Navigation Systems, Estimation and Bayesian Filtering http://bayesclasses.sf.net ___________________________________