Incidentally, your message is very timely. Joel and I have just been discussing off-list the possibilities opened up by giving users access to Phoenix expressions at this level. It's really very exciting.
Indeed very timely. See also:http://tinyurl.com/37mguzo "phoenix domain language (to write mathematical formulas)"
right, since C++ is "mathematical enough" (or as mathematical as it can be with the small set of available symbols [+,-,/,*,==]) then phoenix is mathematical enough, creating a mathematical DSEL on proto probably won't be better than phoenix [except for very specific mathematical area, e.g. tensor manipulation] this discussion is very nice, and now that you know the context maybe I can recast the question: I am extracting a subexpression (don't know the exact name in phoenix jargon) called LambdaExp, by recognizing the pattern actor<composite< divides_eval, vector< LambdaExp, composite< minus_eval, vector< argument<0>, boost::phoenix::value< quantity<UnitIntegrandDomain> > > > > > > f_expr now I want to use this LambdaExp (extracted as at_c<0>(f_expr)) applied to a bind expression, and subsecuently binded. ie in a composition of this kind, with the functions 'value' and 'from_value'. value( LambdaExp (from_value( x) ) ) (this in the context of boost.units is necesary to adimensionalize an expression, apply a normal function and then restore de dimension), this is the closest I got but doesn't work: bind( &result_type::value, actor<LambdaExp>(at_c<0>(f_expr))( // Question: what goes here? to apply the subexpr. bind( &quantity<UnitIntegrandDomain>::from_value, arg_names::arg1 ) ) // end here ); Thank you, Alfredo