Hi, I tried follwoing the tutorial to create new functions to use in Proto but it failed. Let's say I want to have a new unary function called worker that create an expression that ought to be matched by the following grammar : struct worker_grammar : or_< terminal< user_func<_> >, function< worker_tag, terminal< user_func<_> > > {}; I keep getting a 'no type named proto_expr_base in worker_tag' error. Related question, how can I make a new function which tag is a tempalte class whose tempalte parameter is used to change how the associated transform is performed, I tried : struct worker_grammar : or_< terminal< user_func<_> >, function< worker_tag<_>, terminal< user_func<_> > > {}; but it failed too. Thanks in advance -- Joel FALCOU Research Engineer @ Institut d'Electronique Fondamentale Université PARIS SUD XI France