Dynamic function call question
Hello, I've been trying to design a function dispatch system and I was wondering if the following is possible with the current boost libraries... I currently parse json data into an vector of variants, I would like to be able to take those variants and invoke an arbitrary boost function object with a consistent return type. Is it possible to determine the function argument types, get the typed value from the proper index in the array of variants, and call the function with arguments? This sounds like something the boost fusion library might be able to do, but I can't find any example code using the library to see if this is the right fit for the capabilities of the library or if what I'm looking to do is not possible without tons of boiler plate. Any insight would be greatly appreciated, Regards, Daniel Perry
AMDG Perry, Daniel wrote:
I've been trying to design a function dispatch system and I was wondering if the following is possible with the current boost libraries...
I currently parse json data into an vector of variants, I would like to be able to take those variants and invoke an arbitrary boost function object with a consistent return type.
Is it possible to determine the function argument types, get the typed value from the proper index in the array of variants, and call the function with arguments?
This sounds like something the boost fusion library might be able to do, but I can't find any example code using the library to see if this is the right fit for the capabilities of the library or if what I'm looking to do is not possible without tons of boiler plate.
Is apply_visitor what you are looking for? http://www.boost.org/doc/html/boost/apply_visitor.html In Christ, Steven Watanabe
I've been trying to design a function dispatch system and I was wondering if the following is possible with the current boost
AMDG Perry, Daniel wrote: libraries...
I currently parse json data into an vector of variants, I would like to be able to take those variants and invoke an arbitrary boost function object with a consistent return type.
Is it possible to determine the function argument types, get the typed
value from the proper index in the array of variants, and call the function with arguments?
This sounds like something the boost fusion library might be able to do, but I can't find any example code using the library to see if this
is the right fit for the capabilities of the library or if what I'm looking to do is not possible without tons of boiler plate.
Is apply_visitor what you are looking for? http://www.boost.org/doc/html/boost/apply_visitor.html In Christ, Steven Watanabe Steven, No I was aware of the visitors. I am thinking more along the lines of template< Signature> void Execute( vector<variant> args, function<Signature> & Fun ) { fusion::vector< parameter_types<Signature>::type > typed_args( magic_happens_here(args)); fusion::invoke_procedure(Fun, typed_args); } What can I do to make the magic happen? Regards, Daniel Perry
On Thu, Feb 26, 2009 at 6:53 PM, Perry, Daniel
AMDG
I've been trying to design a function dispatch system and I was wondering if the following is possible with the current boost
Perry, Daniel wrote: libraries...
I currently parse json data into an vector of variants, I would like to be able to take those variants and invoke an arbitrary boost function object with a consistent return type.
Is it possible to determine the function argument types, get the typed
value from the proper index in the array of variants, and call the function with arguments?
This sounds like something the boost fusion library might be able to do, but I can't find any example code using the library to see if this
is the right fit for the capabilities of the library or if what I'm looking to do is not possible without tons of boiler plate.
Is apply_visitor what you are looking for? http://www.boost.org/doc/html/boost/apply_visitor.html
In Christ, Steven Watanabe
Steven,
No I was aware of the visitors. I am thinking more along the lines of
template< Signature> void Execute( vector<variant> args, function<Signature> & Fun ) { fusion::vector< parameter_types<Signature>::type > typed_args( magic_happens_here(args)); fusion::invoke_procedure(Fun, typed_args); }
What can I do to make the magic happen?
Regards,
Daniel Perry
Seems, to me you are looking for multi-methods, which might become the part of the next standard. I can only find this document describing the approach, but there is no status on it: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2216.pdf
From this document you might also be able to derive you solution.
Ovanes
AMDG Perry, Daniel wrote:
No I was aware of the visitors. I am thinking more along the lines of
template< Signature> void Execute( vector<variant> args, function<Signature> & Fun ) { fusion::vector< parameter_types<Signature>::type > typed_args( magic_happens_here(args)); fusion::invoke_procedure(Fun, typed_args); }
What can I do to make the magic happen?
So the function has a fixed signature?
You'll need to adapt a vector to the fusion interface.
The easiest way it to convert it to a boost::array (which is a fusion
sequence)
and use transform (untested).
struct variant_get {
template<class Sig>
struct result {
typedef typename boost::mpl::at_c
participants (3)
-
Ovanes Markarian -
Perry, Daniel -
Steven Watanabe