Given example below, is there any way to enforce parameter type strictness? [-- Example begin: #include <boost/function.hpp> using namespace boost; // some kind of callback sig. // typedef function1<void, int &> signature; void fn1(int v) // notice arg by-value (say, user typo) { // here, assignments to `v' are lost after // return } void fn2(int & v) // OK { // here, assignments to `v' are // preserved after return } int main(int, char**) { // I want this to fail at compile-time... signature f1 = fn1; // ...and this to work signature f2 = fn2; return 0; } -- code end] On my compiler (g++ (GCC) 4.0.2 20051125) everything compiles fine but ideally, I'd like to fail the first case. Rationale: Users of my library register callbacks and occasionally mistype their function signature which causes them to modify temporaries rather than "out" variables. Thanks, -- Slawomir Lisznianski Paramay Group, LLC "Programs for Research Machinery"