Joel Falcou wrote:
Eric Niebler a écrit :
You can use proto::if_ with some mpl meta-functions and proto::arity_of. See below: Ah, I missed that v_v Times to print out the new docs and pin it on my office walls
struct ArityLessThan3 : proto::or_< proto::terminal<_> , proto::and_< proto::function< proto::vararg<ArityLessThan3> > , proto::if_< mpl::less< proto::arity_of<_>, mpl::long_<4>
() > > > {}; Shouldn't it be : proto::function< _, proto::vararg<ArityLessThan3> > ? or does vararg also count the function tag ?
No, proto::function< proto::vararg<X> > is equivalent to proto::nary_expr< proto::tag::function, proto::vararg<X> >. Note also that we compare to 4 instead of 3 above because Proto considers an expression like i(i,i,i) to have arity 4 ... because there are four child expressions. HTH, -- Eric Niebler BoostPro Computing http://www.boostpro.com