[Boost-users] [Boost.function_types] Function synthesis and property tags

Subject: [Boost-users] [Boost.function_types] Function synthesis and property tags
From: Yury Korobkin (yuryk_at_[hidden])
Date: 2009-08-24 04:12:05

Hi, everybody.

I'm trying to synthesize a function type G from another function type F
with some changes on return and arg types. What I need to leave
constant, are all these additional properties that are returned by
components<F>::tag. I want them all as a bunch, don't really fancy
querying them one by one, they sorta look contradictive or at least
redundant. 

The naive approach of passing the same tag to the function_type<Seq,
Tag> does not make a change - 
it leads to the same result as if default null_tag were passed. 

How do you generate a function type with the same additional properties
as the given one?

 

Sample code: 
//----------------------------------------------------------------------
---------------------------- 

typedef int (__stdcall * pF)(char); 

typedef int (          * pG)(char);

 

typedef remove_pointer<pF>::type                       F; 

typedef components<F>                             compsF; 

 

// generate type hopefully like pF

typedef function_pointer<compsF,

                             //create tag from mask and bits 

                             detail::property_tag<compsF::bits::value,
compsF::mask::value> 

                            >::type pfn_gen; 

 

BOOST_MPL_ASSERT((is_same<pfn_gen, pG>));                   // this one
passes, should fail, though 

BOOST_MPL_ASSERT((is_same<pfn_gen, pF>));                   // I wish,
but fails 

//----------------------------------------------------------------------
----------------------------

 

Thanks,

YuryK

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