Still the following is not clear: What is the main difference of unevaluated<> to different types of callables like - function pointers - class instances with operator() - lambdas Any of those can be chosen to return a value, so they not only can be called, but evaluated. According to the paper, unevaluated<> can be evaluated several times. Is it the use as function parameters? Any of the callables above can be used as function parameters. Is it the type erasure? labmdas typically would need template functions. Is it the specific syntax? -----Ursprüngliche Nachricht----- Von:Lorand Szollosi via Std-Proposals <std-proposals_at_[hidden]> Uneval is completely different from lambdas [...] What lambda stands for is a callable thing (function-like or procedure-like); what uneval stands for is something you can request to be evaluated.