Re: [Boost-users] [Proto] How to access the grammar of an expression?

Roland Bock wrote:

On 09/24/2010 02:33 PM, Roland Bock wrote:

...

Hi,

ist there a way to access the grammar that was used to construct an expression?

I have defined a metafunction

template struct grammar_less: mpl::false_ {};

which has specialization for some grammar combinations.

Now I want to define a function that can take two arguments so that

child0.grammar < child1.grammar

Any idea how to do that? My test-code is attached.

Regards,

Roland

Hi,

since I know the structure of the types in question, I can circumvent the problem as shown in the attached code. Not nice, but I could probably use it.

Regards,

Roland

you can compute that type information directly in your proto transform: struct sorted_argument_function: proto::and_ < proto::function, proto::if_ < grammar_less< proto::_value(proto::_child0(proto::_child1)) , proto::_value(proto::_child0(proto::_child2))>() > > {}; btw: there is a proto specific list: proto@lists.boost.org