Hi Eric, Thank you for the LHS grammar. I have made the changes you suggested in the attached files. The main header <math.h> (I'll change this name later) includes constants (c0 ... c100), variables(x0... x100 and x y z S r q v t), basic functions from <cmath> and general functions defined by the user, with dimensions 0 to 100. Question1: With PP, I define constants c0 to c100, as non-const because I let the user initialize them to a integer variables or literals or floating point variables or literals. Does the non-constness matter? They are defined in a header file included by users of the library. Question2: With PP, I also define variables. I had variable_tag as a template taking <unsigned int subscript>. Not subscript has nothing to do with the dimensionality here. These are just different 1d variables. But then to match the proto:_ in the grammar, I high jacked your idea of a numerical MPL metafunction mpl::size_t<> for variables as well. Also, note the non-constness?? What do you think of the stand alone x y z S .... non subscripted variables? Queestion3: I made dimension_of a numerical metafunction with an embedded value member. What is the convenience of making metafunctions numerical? Should dimension_of be specialized for function_tag<> templates rather than on any type, as: template <size_t dim> struct dimension_of< function_tag< mpl::size_t<dim> > > { ... }; Any advantage to this? Question4: What is a quick way to test fundef_lhs_grammar does what I intend? Thank you for your help, Regards, -----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Eric Niebler Sent: 03 February 2009 17:46 To: boost-users@lists.boost.org Subject: Re: [Boost-users] proto: analytical-only math functions Hi Hicham, Hicham Mouline wrote:
Hello,
There are a few posts these days about generic libraries for math derivation of math functions, analytically or numerically.
<snip>
template <size_t dim =1> struct function_tag {};
Use MPL Integral Constants here instead: template<typename dim = mpl::size_t<1> > struct function_tag { typedef dim dimension; }; And define a dimension_of metafunction like this: template<typename FunTag> struct dimension_of { typedef typename FunTag::dimension type; };
I want to have 0 variables (nothing) for the 0-dim function in the proto::function case, and I want to have exactly dim variables in the dim>0 proto::function case.
Is it possible to "math-define" the function at the same time of the function<> object definition (in c++ terms) and have the dimension deducted, like:
function f(x,y,z) = x+y+z ;
Yes. Your LHS grammar should look something like this (untested): struct lhs_grammar : proto::or_< // lone functions are ok proto::terminal< function_tag< mpl::size_t<0> > > , proto::and_< // f(x,y,z,...) is ok ... proto::function< proto::terminal< function_tag< proto::_ > > , proto::vararg< proto::terminal< variable_tag > > > // ... as long as the dimension of the function // matches the number of arguments. , proto::if_< mpl::equal_to< dimension_of< proto::_value(proto::_child0) > , mpl::prior<proto::arity_of<proto::_> > >() > > > {}; HTH, -- Eric Niebler BoostPro Computing