Re: [boost] [Boost.Parameter] questions and advice

From: Cédric Venet (cedric.venet_at_[hidden])
Date: 2007-07-10 10:00:32

Quoting Andrew Sutton <asutton_at_[hidden]>:

>
> On Jul 10, 2007, at 9:02 AM, Cédric Venet wrote:
>> boost.optional should serve your purpose.
>
> I had previously considered that as an option (no pun).
> Unfortunately, I don't think this helps if I choose to adopt a
> compile-time function selection. Otherwise, it would work very nicely
> at runtime. I've still got it on my short list of solutions.
>

first, doing compile time dipatching is only usefull if your function  
is very short and the additionnal function call time is relevant (I  
don't think it is the case for you).

If you really want a compile time dispatch, you can try to use mpl in  
order to find out if the parameter is in the ArgumentPack and dispatch  
on the result. from the doc:

"""
An ArgumentPack is a collection of tagged references to the actual  
arguments passed to a function. Every ArgumentPack is also a valid MPL  
Forward Sequence consisting of the keyword tag types in its tagged  
references.
"""

so it shouldn't be to hard to do. But you trade compile time versus  
runtime (and the runtime loss of dynamique dispatch is pretty low).

for your other question:

"""
7   Configuration Macros
7.1   BOOST_PARAMETER_MAX_ARITY
Determines the maximum number of arguments supported by the library.  
Will only be #defined by the library if it is not already #defined.
Defined in:	boost/parameter/config.hpp
Default Value:	5
"""

so you can easily augment this (at the cost of some compile time probably)

doc link => http://www.boost.org/libs/parameter/doc/html/reference.html